143 Sentences With "intermediate frequency"

TMEM171 has signatures of balancing selection, which include a significant excess of polymorphisms and intermediate-frequency alleles.

Transmitters also must adhere to a spectral mask, to prevent adjacent-channel interference, intermediate frequency interference, and intermodulation.

Superheterodyne transmitter is a radio or TV transmitter which uses an intermediate frequency signal in addition to radio frequency signal.

There may be several such stages of intermediate frequency in a superheterodyne receiver; two or three stages are called double (alternatively, dual) or triple conversion, respectively.

The result is a demodulated output just as would be obtained from a superheterodyne receiver using synchronous detection (a product detector) following an intermediate frequency (IF) stage.

Another design, modified circuit. A piezofilter is used in the intermediate frequency path. In Audio power amplifier two diodes are used instead of resistors to set the mode of the output stage.

For example, a key component of a superheterodyne receiver is a mixer used to move received signals to a common intermediate frequency. Frequency mixers are also used to modulate a carrier signal in radio transmitters.

Each lead had a different color since relative polarity or phase was more important for these transformers. Intermediate-frequency tuned transformers were coded blue and red for the primary and green and black for the secondary.

The IF stage from a Motorola 19K1 television set circa 1949. In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. Intermediate frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is done.

The second switching stage mixes the intermediate frequency to baseband. By connecting the two switching stages in series, current is reused and harmonic content from the first stage is fed into the second stage thereby improving the mixer gain.

Most superheterodyne receivers use a variable-frequency oscillator, mixer, and filter to tune the desired signal to a common intermediate frequency or baseband, where it is then sampled by the analog-to-digital converter. However, in some applications it is not necessary to tune the signal to an intermediate frequency and the radio frequency signal is directly sampled by the analog-to-digital converter (after amplification). Real analog-to-digital converters lack the dynamic range to pick up sub-microvolt, nanowatt-power radio signals. Therefore, a low-noise amplifier must precede the conversion step and this device introduces its own problems.

After sound (amplitude modulation, AM) transmission began around 1920, the term evolved to mean a demodulator, (usually a vacuum tube) which extracted the audio signal from the radio frequency carrier wave. This is its current meaning, although modern detectors usually consist of semiconductor diodes, transistors, or integrated circuits. In a superheterodyne receiver the term is also sometimes used to refer to the mixer, the tube or transistor which converts the incoming radio frequency signal to the intermediate frequency. The mixer is called the first detector, while the demodulator that extracts the audio signal from the intermediate frequency is called the second detector.

Block diagram of a typical superheterodyne receiver. Red parts are those that handle the incoming radio frequency (RF) signal; green are parts that operate at the intermediate frequency (IF), while blue parts operate at the modulation (audio) frequency. An important and widely used application of the heterodyne technique is in the superheterodyne receiver (superhet), which was invented by U.S. engineer Edwin Howard Armstrong in 1918. In the typical superhet, the incoming radio frequency signal from the antenna is mixed (heterodyned) with a signal from a local oscillator (LO) to produce a lower fixed frequency signal called the intermediate frequency (IF) signal.

During the development of radar in World War II, the superheterodyne principle was essential for downconversion of the very high radar frequencies to intermediate frequencies. Since then, the superheterodyne circuit, with its intermediate frequency, has been used in virtually all radio receivers.

Negative bias is applied to the grid to bring the plate current almost to cutoff.J. Scott-Taggart, The Manual of Modern Radio, London: The Amalgamated Press LTD., 1933, p. 115 The grid is connected directly to the secondary of a radio frequency or intermediate frequency transformer.

Ferrite-core transformers are widely used in (intermediate frequency) (IF) stages in superheterodyne radio receivers. They are mostly tuned transformers, containing a threaded ferrite slug that is screwed in or out to adjust IF tuning. The transformers are usually canned (shielded) for stability and to reduce interference.

Paul Horowitz, Winfred Hill The Art of Electronics Second Edition, Cambridge University Press 1989, pp. 885–887. For example, a communications receiver might contain two mixer stages for conversion of the input signal to an intermediate frequency and another mixer employed as a detector for demodulation of the signal.

Signal reception is invariably done via a superheterodyne receiver: the first stage is a tuner which selects a television channel and frequency-shifts it to a fixed intermediate frequency (IF). The signal amplifier performs amplification to the IF stages from the microvolt range to fractions of a volt.

World Health Organization. Retrieved Aug 2013. However, many studies have been conducted with electromagnetic fields to investigate their effects on cell metabolism, apoptosis, and tumor growth. Electromagnetic radiation in the intermediate frequency range has found a place in modern medical practice for the treatment of bone healing and for nerve stimulation and regeneration.

Mixing the two created an intermediate frequency of 50 kHz, which was well within the capability of the tubes. The name "superheterodyne" was a contraction of "supersonic heterodyne", to distinguish it from receivers in which the heterodyne frequency was low enough to be directly audible, and which were used for receiving "continuous wave" (CW) Morse code transmissions (not speech or music). After the war, in 1920, Armstrong sold the patent for the superheterodyne to Westinghouse, who subsequently sold it to RCA. The increased complexity of the superheterodyne circuit compared to earlier regenerative or tuned radio frequency receiver designs slowed its use, but the advantages of the intermediate frequency for selectivity and static rejection eventually won out; by 1930, most radios sold were 'superhets'.

Above: Direct modulation, below superheterodyne transmitter There are two types of transmitters. In some transmitters, the information signal (audio (AF), video (VF) etc.) modulates the radio frequency (RF) signal. These direct modulation transmitters are relatively simple transmitters. In more complicated transmitters which are called superheterodyne, the information signal modulates an intermediate frequency (IF) signal.

The difference frequency is then amplified and filtered in an 'intermediate frequency' or i.f. amplifier before being converted back to audible frequencies again. This design, which is based on standard radio design, gives improved frequency discrimination and avoids problems with interference from the local oscillator. In more recent DSP-based detectors, the heterodyne conversion can be done entirely digitally.

Conversion to an intermediate frequency is useful for several reasons. When several stages of filters are used, they can all be set to a fixed frequency, which makes them easier to build and to tune. Lower frequency transistors generally have higher gains so fewer stages are required. It's easier to make sharply selective filters at lower fixed frequencies.

Every baseband has a unique Electronic Serial Number (or Sirius ID). Another major section of a Sirius receiver is the tuner. The tuner is also a custom ASIC, the STA210. The tuner connects to the antenna, and receives the incoming satellite and terrestrial signals at 2.315 GHz and downconverts them to intermediate frequency signals at around 75 MHz.

The next level in integration is "software-defined radio", where all filtering, modulation and signal manipulation is done in software. This may be a PC soundcard or by a dedicated piece of DSP hardware. There will be a RF front-end to supply an intermediate frequency to the software defined radio. These systems can provide additional capability over "hardware" receivers.

Alternatively, a signal may be intentionally oversampled without an intermediate frequency to reduce the requirements on the anti-alias filter. For example, CD audio typically extends up to 20 kHz, but is sampled with a 22.05 kHz Nyquist rate. By oversampling by 2.05 kHz, both aliasing and attenuation of higher audio frequencies can be prevented even with less than ideal filters.

High current power-frequency devices, such as electric motors, generators and transformers, use multiple small conductors in parallel to break up the eddy flows that can form within large solid conductors. The same principle is applied to transformers used at higher than power frequency, for example, those used in switch-mode power supplies and the intermediate frequency coupling transformers of radio receivers.

This had originally been a television receiver designed by Pye Ltd. to pick up BBC transmissions on 45 MHz. It was adapted to the MK. IV's ~200 MHz by using it as the intermediate frequency stage of a superheterodyne system. To do this, they had added another tube that stepped down the frequency from the radar's 193 MHz to 45 MHz.

Another change was to move from the early-war standard of 60 MHz intermediate frequency to a new receiver strip working at 13.5 MHz. These changes reduced the receiver system noise by about 2 dB. In addition, new anti-jamming systems were added. This consisted of a third stage in the IF receiver that could optionally be switched in if jamming was seen.

AST/RO also had a Nasymth focus accessed by the removal of the fourth mirror. Over its lifetime, AST/RO observed with five heterodyne receivers. These receivers operated at 230 GHz, 450-495 GHz (two), 800-820 GHz, and an array of four 800-820 GHz. AST/RO was able to process seven intermediate- frequency bandpasses using acousto-optical spectrometers.

A roofing filter is a type of filter used in a HF radio receiver. It is usually found after the first receiver mixer. The goal of a roofing filter is to limit the passband of the first intermediate frequency (IF) stage. Strong signals outside the channel which may cause overloading and distortion by the following amplifier stages and mixers are blocked.

The crystal's stability and its high Q factor allow crystal filters to have precise center frequencies and steep band-pass characteristics. Typical crystal filter attenuation in the band-pass is approximately 2-3dB. Crystal filters are commonly used in communication devices such as radio receivers. A crystal filter is very often found in the intermediate frequency (IF) stages of high-quality radio receivers.

A typical analog monochrome television receiver is based around the block diagram shown below: alt=block diagram of a television receiver showing tuner, intermediate frequency amplifier. A demodulator separates sound from video. Video is directed to the CRT and to the synchronizing circuits. The tuner is the object which "plucks" the television signals out of the air, with the aid of an antenna.

There are two types of tuners in analog television, VHF and UHF tuners. The VHF tuner selects the VHF television frequency. This consists of a 4 MHz video bandwidth and a 2 MHz audio bandwidth. It then amplifies the signal and converts it to a 45.75 MHz Intermediate Frequency (IF) amplitude-modulated picture and a 41.25 MHz IF frequency-modulated audio carrier.

In the superheterodyne, the radio frequency signal from the antenna is shifted down to a lower "intermediate frequency" (IF), before it is processed. Terman, Frederick E. (1943) Radio Engineers' Handbook, p. 636-638 The incoming radio frequency signal from the antenna is mixed with an unmodulated signal generated by a local oscillator (LO) in the receiver. The mixing is done in a nonlinear circuit called the "mixer".

The result at the output of the mixer is a heterodyne or beat frequency at the difference between these two frequencies. The process is similar to the way two musical notes at different frequencies played together produce a beat note. This lower frequency is called the intermediate frequency (IF). The IF signal also has all the information that was present in the original RF signal.

Almost all Indian members of haplogroup L are L1 derived, with L3-M357 occurring only sporadically (0.4%). Conversely in Pakistan, L3-M357 subclade account for 86% of L-M20 chromosomes and reaches an intermediate frequency of 6.8%, overall. L1-M76 occurs at a frequency of 7.5% in India and 5.1% in Pakistan, exhibiting peak variance distribution in the Maharashtra region in coastal western India.

Yet another technique that could determine the frequency to which a receiver is tuned was the technique of Operation RAFTER, which listened for the direct or additive frequency of the local oscillator in a superheterodyne receiver. This technique can be countered by shielding the intermediate frequency circuitry of superheterodyne receivers, or moving into software-defined radio using digital signal processors with no local oscillator.

The IF stage from a Motorola 19K1 television set circa 1949. More modern IF amplifier and demodulator in integrated circuit form Intermediate-frequency (IF) amplifiers are amplifier stages used to raise signal levels in radio and television receivers, at frequencies intermediate to the higher radio- frequency (RF) signal from the antenna and the lower (baseband) audio or video frequency that the receiver is recovering.

RSSI is often derived in the intermediate frequency (IF) stage before the IF amplifier. In zero-IF systems, it is derived in the baseband signal chain, before the baseband amplifier. RSSI output is often a DC analog level. It can also be sampled by an internal analog-to-digital converter (ADC) and the resulting codes available directly or via peripheral or internal processor bus.

Each receiver comprised a large spherical radome mounted on the top of a 25 m fixed mast. This radome, made of identical segments of polyurethane foam, contained the radio antennas and the microwave components, intermediate frequency preamplifiers and the two-way communications equipment for communicating between central and side sites. At first glance the system bore a striking resemblance to typical Eastern European water towers.

The chipset converts the signals from 2.3 gigahertz (GHz) to a lower intermediate frequency. Sirius also offers an adapter that allows conventional car radios to receive satellite signals. Sirius broadcasts using 12.5 MHz of the S band between 2320 and 2332.5 MHz. Audio channels are digitally compressed using a proprietary variant of Lucent's Perceptual audio coder compression algorithm and encrypted with a proprietary conditional access system.

The sinewave output of an ideal oscillator is a single line in the frequency spectrum. Such perfect spectral purity is not achievable in a practical oscillator. Spreading of the spectrum line caused by phase noise must be minimised in the local oscillator for a superheterodyne receiver because it defeats the aim of restricting the receiver frequency range by filters in the IF (intermediate frequency) amplifier.

When mixing signals to produce a desired output frequency, the choice of Intermediate frequency and local oscillator is important. If poorly chosen, a spurious output can be generated. For example, if 50 MHz is mixed with 94 MHz to produce an output on 144 MHz, the third harmonic of the 50 MHz may appear in the output. This problem is similar to the Image response problem which exists in receivers.

82-87 In a digital receiver, the analog-to-digital converter (ADC) operates at low sampling rates, so input RF must be mixed down to IF to be processed. Intermediate frequency tends to be lower frequency range compared to the transmitted RF frequency. However, the choices for the IF are most dependent on the available components such as mixer, filters, amplifiers and others that can operate at lower frequency.

TR-1, circuit board and casing. Exhibit of Deutsches Museum, Munich 22.5 Volt battery used in the Regency TR-1 (AA battery for comparison shown on left) The TR-1 is a superheterodyne receiver madeRegency schematic with four n-p-n germanium transistors and one diode. It contains a single transistor converter stage, followed by two intermediate- frequency amplifier stages. After detection, a single-transistor stage amplifies the audio frequency.

In telecommunications and signal processing, baseband signals are transmitted without modulation, that is, without any shift in the range of frequencies of the signal. Baseband has a low-frequency—contained within the bandwidth frequency close to 0 hertz up to a higher cut-off frequency. Baseband can be synonymous with lowpass or non-modulated, and is differentiated from passband, bandpass, carrier-modulated, intermediate frequency, or radio frequency (RF).

In order to equalise the low frequency and high frequency components of the VF signal, a filter named a Nyquist filter is used in receivers. This filter, which is used before demodulation, is actually a low-pass filter with 6 dB suppression at the intermediate frequency (IF) carrier. Thus the level of double sideband portion of the VF signal is suppressed and the original band characteristic is reconstructed at the output of the demodulator.

The Receiver, T.3515 or T.3516, took the 13.5 MHz intermediate frequency and amplified it to usable levels. The output was sent to the Indicating unit Type 162, which contained the two CRTs. If it was equipped, the Lucero receiver, TR.3190, was connected to the height display, sitting (electrically) between the receiver and display. Which of these circuits was in use, along with many other controls, was located on the Switch Unit.

Achieving constant sensitivity and bandwidth across an entire broadcast band was rarely achieved. In contrast, a superheterodyne receiver translates the incoming high radio frequency to a lower intermediate frequency which does not change. The problem of achieving constant sensitivity and bandwidth over a range of frequencies arises only in one circuit (the first stage) and is therefore considerably simplified. The major problem with the TRF receiver, particularly as a consumer product, was its complicated tuning.

The receiver was then rebuilt, becoming a super-regenerative set with two intermediate-frequency stages. With this improved receiver, the system readily tracked vessels at up to range. In September 1935, a demonstration was given to the Commander-in- Chief of the Kriegsmarine. The system performance was excellent; the range was read off the Braun tube with a tolerance of 50 meters (less than 1 percent variance), and the lobe switching allowed a directional accuracy of 0.1 degree.

A vector signal analyzer operates by first down-converting the signal spectra by using superheterodyne techniques. A portion of the input signal spectrum is down-converted (using a voltage-controlled oscillator and a mixer) to the center frequency of a band- pass filter. The use of a voltage-controlled oscillator allows consideration of different carrier frequencies. After the conversion to an intermediate frequency, the signal is filtered in order to band-limit the signal and prevent aliasing.

A radar detector detector (RDD) is a device used by police or law enforcement in areas where radar detectors are declared illegal. Radar detectors are built around a superheterodyne receiver, which has a local oscillator that radiates slightly. It is therefore possible to build a radar-detector detector, which detects such emissions (usually the frequency of the radar type being detected, plus about 10 MHz for the intermediate frequency). Some radar guns are equipped with such a device.

The bandwidth of a filter is proportional to its center frequency. In receivers like the TRF in which the filtering is done at the incoming RF frequency, as the receiver is tuned to higher frequencies its bandwidth increases. The main reason for using an intermediate frequency is to improve frequency selectivity. In communication circuits, a very common task is to separate out or extract signals or components of a signal that are close together in frequency.

In TV transmitters, both AF and VF modulate intermediate frequency (IF) carriers. (The frequency difference between the two carriers is 4.5 MHz in System M and 5.5 MHz in System B/G) Then the modulated IF signals are added either at the output of the vision modulator or at the output of the vestigial sideband stage. In both cases, the added signals are low level signals and no special combining circuitry is required. Frequency conversion and amplification is common.

More complex transmissions like PAL/NTSC (TV), DAB (digital radio), DVB-T/DVB-S/DVB-C (digital TV) etc. use a wider frequency bandwidth, often with several subcarriers. These are transmitted inside the receiver as an intermediate frequency (IF). Subcarriers are then processed like real radio transmissions, but the whole bandwidth is sampled with an analog-to-digital converter (A/D) at a rate faster than the Nyquist rate (that is, at least twice the IF frequency).

Many of the roots that nourished the work of the Hammond group and its contemporaries were recorded in our paper: the pioneering work of Wilson and Evans, Tesla, Shoemaker, in basic radiodynamics; . . . of Tesla and Fessenden leading to the development of basic intermediate frequency circuitry. Fessenden's receiver did not see much application because of its local oscillator's stability problem. A stable yet inexpensive local oscillator was not available until Lee de Forest invented the triode vacuum tube oscillator.

A computer is a typical example, where spurious emissions may not be contained within the case. A radio receiver will often use an intermediate frequency which is detectable outside the radio--the concept behind at least one audience measurement concept for roadside detection of radio stations which passing motorists are listening to. Other examples include the motor, transformer, dimmer, and corona from electrical powerlines. Unintentional radiation from these devices can create interference on AM radio, and on the video of television stations.

Practically all modern receivers are of the superheterodyne design. The RF signal from the antenna may have one stage of amplification to improve the receiver's noise figure, although at lower frequencies this is typically omitted. The RF signal enters a mixer, along with the output of the local oscillator, in order to produce a so-called intermediate frequency (IF) signal. An early optimization of the superheterodyne was to combine the local oscillator and mixer into a single stage called "converter".

Shortly after Armstrong invented the superheterodyne, a triode mixer stage design was developed that not only mixed the incoming signal with the local oscillator, but the same valve doubled as the oscillator. This was known as the autodyne mixer. Early examples had difficulty oscillating across the frequency range because the oscillator feedback was via the first intermediate frequency transformer primary tuning capacitor, which was too small to give good feedback. Also keeping the oscillator signal out of the antenna circuit was difficult.

Interrogating pulses are directed from the antenna to the receiver, and reply pulses are directed from the transmitter to the antenna. The preselector, consisting of three coaxial cavities, attenuates all RF signals outside the receiving band. The received signal is heterodyned to a 50 MHz intermediate frequency in the mixer and amplified in the IF amplifier which also contains the detector. In case of coded transmission, the decoder module provides a pulse output only if the correct spacing exists between pulse pairs received.

Under conditions of jamming, the P-unit fires on the amplitude peaks of the beat cycle where the two waves constructively interfere. So, a combined stimulus-EOD signal will cause T-units to fire at the intermediate frequency, and cause P-unit firing to increase and decrease periodically with the beat.Scheich, H., Bullock, T., Hamstra, Jr., R. (1973) Coding properties of two classes of afferent nerve fibers: high-frequency electroreceptors in the electric fish, Eigenmannia. J. Neurophysiol. 36:39-60.

Tuning of the R-390A's radio frequency and intermediate frequency front end is synchronized by means of an ingenious mechanical system of racks, gears, and cams. When the front panel tuning controls are rotated, this system raises and lowers ferrite slugs in and out of the receiver's tuning coils. This ensures that all front- end circuits are tracked, meaning all circuits are tuned to the correct frequency to maintain excellent selectivity and sensitivity. The receiver's construction is modular for easy servicing.

The first used a tunable klystron and crystal detector to produce an intermediate frequency (IF) of 65 MHz which then went through a two-stage amplifier. The result was then mixed down to a new IF of 10 MHz and into a three-stage amplifier. A final rectifier produced a signal that was fed directly into the Y-axis deflection plates of the CRTs. Which CRT to feed the signal two was controlled by the phase of the smaller alternator.

At the receiver side, the demodulator typically performs: # Bandpass filtering. # Automatic gain control, AGC (to compensate for attenuation, for example fading). # Frequency shifting of the RF signal to the equivalent baseband I and Q signals, or to an intermediate frequency (IF) signal, by multiplying the RF signal with a local oscillator sine wave and cosine wave frequency (see the superheterodyne receiver principle). # Sampling and analog-to-digital conversion (ADC) (sometimes before or instead of the above point, for example by means of undersampling).

Early pioneer Jeffery Collins incorporated surface acoustic wave devices in a Skynet receiver he developed in the 1970s. It synchronised signals faster than existing technology. They are also often used in digital receivers, and are well suited to superhet applications. This is because the intermediate frequency signal is always at a fixed frequency after the local oscillator has been mixed with the received signal, and so a filter with a fixed frequency and high Q provides excellent removal of unwanted or interference signals.

McNicol, Donald (1946) Radio's Conquest of Space, p. 267-270 After this it became the standard method of receiving CW radiotelegraphy. The heterodyne oscillator is the ancestor of the beat frequency oscillator (BFO) which is used to receive radiotelegraphy in communications receivers today. The heterodyne oscillator had to be retuned each time the receiver was tuned to a new station, but in modern superheterodyne receivers the BFO signal beats with the fixed intermediate frequency, so the beat frequency oscillator can be a fixed frequency.

The ATA Offset Gregorian Design The ATA-42 configuration will provide a maximum baseline of 300 m (and ultimately for the ATA-350, 900 m). A cooled log-periodic feed on each antenna is designed to provide a system temperature of ~45K from 1–10 GHz, with reduced sensitivity in the ranges of 0.5–1.0 GHz and 10–11.2 GHz. Four separate frequency tunings (IFs) are available to produce 4 x 100 MHz intermediate frequency bands. Two IFs support correlators for imaging; two will support SETI observing.

They are common in precision circuitry like A/V components, and may need to be adjusted when the equipment is serviced. Trimpots are often used to initially calibrate equipment after manufacturing. Unlike many other variable controls, trimmers are mounted directly on circuit boards, turned with a small screwdriver and rated for many fewer adjustments over their lifetime. Trimmers like trimmable inductors and trimmable capacitors are usually found in superhet radio and television receivers, in the intermediate frequency (IF), oscillator and radio frequency (RF) circuits.

In early 1937 the Airborne Group received a number of Western Electric Type 316A doorknob vacuum tubes. These were suitable for building transmitter units of about 20 W continual power for wavelengths of 1 to 10 m. Percy Hibberd built a new push–pull amplifier using two of these tubes working at 1.25 m wavelength; below 1.25 m the sensitivity dropped off sharply. Gerald Touch converted the EMI receiver to the same frequency by using it as the intermediate frequency portion of a superheterodyne circuit.

A cascode circuit is very useful as a multiplying mixer circuit in superheterodyne receivers. At the lower gate the RF signal is fed to the mixer, and at the upper gate the local oscillator signal is fed to the mixer. Both signals are multiplied by the mixer, and the difference frequency, the intermediate frequency, is taken from the upper drain of the cascode mixer. This was further developed by cascoding whole differential- amplifier stages to form the balanced mixer, and then the Gilbert cell double- balanced mixer.

This circuit made radio receivers more sensitive and selective and is extensively used today. The key feature of the superheterodyne approach is the mixing of the incoming radio signal with a locally generated, different frequency signal within a radio set. This circuit is called the mixer. The result is a fixed, unchanging intermediate frequency, or I.F. signal which is easily amplified and detected by following circuit stages. In 1919, Armstrong filed an application for a US patent of the superheterodyne circuit which was issued the next year.

The broadcast studios were located at 108 E. Walnut in downtown Salina and programmed Top-40 music to a teen audience and the servicemen at Schilling Air Base, which was still operational in 1964. By the late 1970s KINA was broadcasting country music. KINA's dial position at 910 kHz would prove troublesome, as it was exactly on the second harmonic of radios with a 455 kHz IF (intermediate frequency). This resulted in an annoying tone or whistle in the background of the station's programming on home radios.

Mechanical filters quickly also found popularity in VHF/UHF radio intermediate frequency (IF) stages of the high end radio sets (military, marine, amateur radio and the like) manufactured by Collins. They were favoured in the radio application because they could achieve much higher Q-factors than the equivalent LC filter. High Q allows filters to be designed which have high selectivity, important for distinguishing adjacent radio channels in receivers. They also had an advantage in stability over both LC filters and monolithic crystal filters.

Modern Signal Analyzer Architecture Modern signal analyzers use a superheterodyne receiver to downconvert a portion of the signal spectrum for analysis. As shown in the figure to the right, the signal is first converted to an intermediate frequency and then filtered in order to band-limit the signal and prevent aliasing. The downconversion can operate in a swept-tuned mode similar to a traditional spectrum analyzer, or in a fixed-tuned mode. In the fixed- tuned mode the range of frequencies downconverted does not change and the downconverter output is then digitized for further analysis.

The 12AT7 high-mu dual triode was designed primarily for RF mixing applications where it was incorporated into the oscillator/mixer stage and used to heterodyne incoming RF signals with the local oscillator to create an intermediate frequency in TV and FM sets. Thus, it is intentionally designed to be extremely non-linear. Thus, circuits based around the 12AT7 exhibit a larger degree of non-linearity throughout the entire dynamic operating range, including the middle. As a result, it produces greater even-order harmonic distortion (less objectionable than odd-order distortion).

When the stimulus frequency and discharge frequency are close to each other, the two amplitude-time waves will undergo interference, and the electroreceptive organs will perceive a single wave with an intermediate frequency. In addition, the combined stimulus-EOD wave will have a beat pattern, with the beat frequency equal to the frequency difference between stimulus and EOD. Gymnotiforms have two classes of electroreceptive organs, the ampullary receptors and the tuberous receptors. Ampullary receptors respond to low-frequency stimulation less than 40 Hz and their role in the JAR is currently unknown.

Each stage used a Class B amplifier arrangement of EF8s, special low noise, "aligned-grid" pentodes. The output of the initial amplifier was then sent to the intermediate frequency mixer, which extracted a user-selectable amount of the signal, 500, 200 or 50 kHz as selected by a switch on the console. The first setting allowed most of the signal through, and was used under most circumstances. The other settings were available to block out interference, but did so by also blocking some of the signal which reduced the overall sensitivity of the system.

In some cases the radio frequency inside the tunnel is different from the one used by the broadcaster. More often the program inside is transmitted on the same frequency as outside, in which case the information signal should be demodulated or converted to an intermediate frequency in the outside receiver, and then modulated/shifted back in the transmitter. Otherwise feedback may occur. Tunnel transmitters are used in Germany only for audio transmitters working in FM-range and for further radio services, such as mobile phone services which also work in this frequency range.

The circuit was designed so as to get the maximum possible gain out of the first three transistors (which operated at radio frequencies). The first transistor used as a frequency converter was operated very close to its VCBO of 30 volts (from the 22.5 volt battery). This gives a larger depletion layer between the collector and the base which reduces the parasitic feedback due to the Miller effect and extends the frequency range. The two intermediate frequency amplifier transistors are neutralised to cancel out their parasitic Miller effect feedback which also extends their frequency range.

VHF/UHF tuner of a television set. The antenna connector is on the right. A tuner is a subsystem that receives radio frequency (RF) transmissions and converts the selected carrier frequency and its associated bandwidth into a fixed frequency that is suitable for further processing, usually because a lower frequency is used on the output. Broadcast FM/AM transmissions usually feed this intermediate frequency (IF) directly into a demodulator that converts the radio signal into audio-frequency signals that can be fed into an amplifier to drive a loudspeaker.

The MidSTAR-1 mission includes a single spacecraft under the command and control of a single satellite ground station (SGS) located at the United States Naval Academy, Annapolis, Maryland. The ground station forwards downlinked data files to the principal investigators via the Internet. The launch segment for MidSTAR-1 utilized an Atlas V launch vehicle through the Space Test Program, placing the satellite in a circular orbit at 496 km altitude, 46 degrees inclination. The satellite uses an uplink at 1.767 GHz with an intermediate frequency (IF) of 435 MHz, and a 2.20226 GHz downlink.

The image rejection ratio, or image frequency rejection ratio, is the ratio of the intermediate-frequency (IF) signal level produced by the desired input frequency to that produced by the image frequency. The image rejection ratio is usually expressed in dB. When the image rejection ratio is measured, the input signal levels of the desired and image frequencies must be equal for the measurement to be meaningful. IMRR is measured in dB, giving the ratio of the wanted to the unwanted signal to yield the same output from the receiver.

In an idealised Wright-Fisher model, the fate of an allele, beginning at an intermediate frequency, is largely determined by selection if the selection coefficient s ≫ 1/N, and largely determined by neutral genetic drift if s ≪ 1/N. In real populations, the cutoff value of s may depend instead on local recombination rates. This limit to selection in a real population may be captured in a toy Wright-Fisher simulation through the appropriate choice of Ne. Populations with different selection effective population sizes are predicted to evolve profoundly different genome architectures.

BUC: Block upconverter, Ku band Top: Hughes 1W Bottom: Feed horn with short section of waveguide, Andrew 2W BUC and Swedish microwave LNB BUC: Block upconverter, Ku band 1.2 Andrew dish assembly A block upconverter (BUC) is used in the transmission (uplink) of satellite signals. It converts a band of frequencies from a lower frequency to a higher frequency. Modern BUCs convert from the L band to Ku band, C band and Ka band. Older BUCs convert from a 70 MHz intermediate frequency (IF) to Ku band or C band.

Beginning in 2010, Press Communications attempted to move WBHX inland and to 99.3 MHz. The intent was to force WZBZ, broadcasting on 99.3 from Atlantic City, to move to 99.7 in return. However, stations that are 10.6 or 10.8 MHz apart (near the typical 10.7 MHz intermediate frequency of FM receivers) must be physically separated by 10 km to avoid causing interference in nearby radios. WZBZ's transmitter site is 2 km from that of WAJM (88.9 FM), and moving to 99.7 would separate the two stations by 10.8 MHz.

The IF signal passes through filter and amplifier stages, then is demodulated in a detector, recovering the original modulation. The receiver is easy to tune; to receive a different frequency it is only necessary to change the local oscillator frequency. The stages of the receiver after the mixer operates at the fixed intermediate frequency (IF) so the IF bandpass filter does not have to be adjusted to different frequencies. The fixed frequency allows modern receivers to use sophisticated quartz crystal, ceramic resonator, or surface acoustic wave (SAW) IF filters that have very high Q factors, to improve selectivity.

Alternating electric field therapy / TTF was initially described in 2004 as the use of insulated electrodes to apply very-low-intensity, intermediate-frequency alternating electrical fields to a target area containing proliferating cells. In preclinical cancer models, TTF appeared to show selective toxicity to proliferating cells through an antimitotic mechanism. Proteins and protein complexes that are critical for mitosis and could be affected by electric fields include α/β-tubulin and the mitotic septin heterotrimer. These molecules possess an uneven distribution of charged amino acid residues (a dipole), that could prevent their normal orientation and function when exposed to alternating electric fields.

Demodulating and Decoding GPS Satellite Signals using the Coarse/Acquisition Gold code. A GPS receiver processes the GPS signals received on its antenna to determine position, velocity and/or timing. The signal at antenna is amplified, down converted to baseband or intermediate frequency, filtered (to remove frequencies outside the intended frequency range for the digital signal that would alias into it) and digitalized; these steps may be chained in a different order. Note that aliasing is sometimes intentional (specifically, when undersampling is used) but filtering is still required to discard frequencies not intended to be present in the digital representation.

Perhaps the most commonly used intermediate frequencies for broadcast receivers are around 455 kHz for AM receivers and 10.7 MHz for FM receivers. In special purpose receivers other frequencies can be used. A dual-conversion receiver may have two intermediate frequencies, a higher one to improve image rejection and a second, lower one, for desired selectivity. A first intermediate frequency may even be higher than the input signal, so that all undesired responses can be easily filtered out by a fixed-tuned RF stage.Wes Hayward, Doug De Maw (ed),Solid state design for the radio amateur, (American Radio Relay League, 1977) pp.

This image from an AI Mk. IV radar is similar in concept to the GL Mk. II, although it displays blips on either side of a centreline rather than as two peaks on one side. The blips are just visible about half- way along the baseline. The large triangles at the top and right are caused by ground reflections, and are not present in GL systems. The range signal was received on a single half-wave dipole mounted at the middle of the horizontal antenna array, fed into a four-tube RF receiver, and then into a four-tube intermediate frequency (IF) system.

The Transmitter/Receiver was also responsible for the first part of the receiver system. A CV43 Sutton tube switched the antenna from the transmitter to receiver side of the system after the pulses were sent. From there it was modulated by a CV101 diode, one of the earliest examples of military-grade solid state electronics and a key element of microwave radars. After the diode, the signal had been reduced in frequency from ~3,300 MHz to a 13.5 MHz intermediate frequency that was then fed back through the aircraft in a coaxial cable to the receiver/amplifier.

Image response (or more correctly, image response rejection ratio, or IMRR) is a measure of performance of a radio receiver that operates on the superheterodyne principle. C-W and A-M Radio Transmitters and Receivers, United States Department of the Army, 1952 page 229 In such a radio receiver, a local oscillator (LO) is used to heterodyne or "beat" against the incoming radio frequency (RF), generating sum and difference frequencies. One of these will be at the intermediate frequency (IF), and will be selected and amplified. The radio receiver is responsive to any signal at its designed IF frequency, including unwanted signals.

The original reason for the invention of the superhet was that before the appearance of the screen-grid valve, there was no type of valve which could give good gain at radio frequencies (i.e. frequencies much above 100 kHz), so a technique was applied whereby the incoming RF signal was "mixed" (i.e. multiplied) with a locally generated oscillatory voltage (the local oscillator) so as to produce a beat frequency of about 30 kHz. This intermediate frequency represented the incoming signal in all important respects, but at a significantly lower frequency which could be successfully amplified by the triode amplifiers available then.

In a low-IF receiver, the RF signal is mixed down to a non-zero low or moderate intermediate frequency, typically a few megahertz (for TV), and even lower frequencies (typically 120-130kHz) in the case of FM radio band receivers. Low-IF receiver topologies have many of the desirable properties of zero-IF architectures, but avoid the DC offset and 1/f noise problems. The use of a non-zero IF re-introduces the image issue. However, when there are relatively relaxed image and neighbouring channel rejection requirements they can be satisfied by carefully designed low-IF receivers.

As a result, no frequency up–down conversion is required at the various base stations, thereby resulting in simple and rather cost-effective implementation is enabled at the base stations. b) In IF-over-fiber architecture, an IF (intermediate frequency) radio signal with a lower frequency is used for modulating light before being transported over the optical link. Therefore, before radiation through the air, the signal must be up-converted to RF at the base station. Access to dead zones An important application of RoF is its use to provide wireless coverage in the area where wireless backhaul link is not possible.

Further confusion was added by a captured Coastal Command pilot, who related that ASV was no longer used for search, but only in the last minutes of the approach. Instead, their aircraft were using a receiver tuned to the Metox intermediate frequency that allowed them to detect the submarines at as much as . This led to an urgent 13 August 1943 message from German Naval High Command ordering that submarines turn off their Metox. This incredible deception not only allowed Mark II to once again become effective but further delayed the German discovery of the true nature of the problem.

A single tunable RF filter stage rejects the image frequency; since these are relatively far from the desired frequency, a simple filter provides adequate rejection. Rejection of interfering signals much closer in frequency to the desired signal is handled by the multiple sharply-tuned stages of the intermediate frequency amplifiers, which do not need to change their tuning. This filter does not need great selectivity, but as the receiver is tuned to different frequencies it must "track" in tandem with the local oscillator. The RF filter also serves to limit the bandwidth applied to the RF amplifier, preventing it from being overloaded by strong out-of-band signals.

Frequency converter may also refer to a much-lower-powered circuit that converts radio frequency signals at one frequency to another frequency, especially in a Superheterodyne receiver. See Frequency mixer. The circuit usually consists of a local oscillator and frequency mixer (analog multiplier) that generates sum and difference frequencies from the input and local oscillator, of which one (the Intermediate frequency) will be required for further amplification, while the others are filtered out. The same result was achieved historically by the pentagrid converter or a Triode and Hexode in a single tube, but can be implemented in transistor radios economically by a single transistor functioning as a self-oscillating mixer.

Because of the high cost of waveguide runs, in many parabolic antennas the RF front end electronics of the receiver is located at the feed antenna, and the received signal is converted to a lower intermediate frequency (IF) so it can be conducted to the receiver through cheaper coaxial cable. This is called a low-noise block downconverter. Similarly, in transmitting dishes, the microwave transmitter may be located at the feed point. An advantage of parabolic antennas is that most of the structure of the antenna (all of it except the feed antenna) is nonresonant, so it can function over a wide range of frequencies, that is a wide bandwidth.

The use of 45.75 MHz as an intermediate frequency within television receivers became commonplace after UHF reception became an option in 1953. Channel 1's signal on this frequency (over the air, or on analogue cable) could create interference internally within television sets. Most cable systems use frequencies below 54 MHz (Channel 2) for communication back to the cable provider from cable modems and digital apparatus, so any "Cable 1" channel needs to avoid operation on the original VHF Channel 1 frequencies from the pre-1948 bandplans. As such, "cable 1" is not related to the original 44–50 MHz VHF channel except in name.

This shift allowed the satellite television DTH industry to change from being a largely hobbyist one where only small numbers of systems costing thousands of US dollars were built, to a far more commercial one of mass production. In the United States, service providers use the intermediate frequency ranges of 950–2150 MHz to carry the signal from the LNBF at the dish down to the receiver. This allows for transmission of UHF signals along the same span of coaxial wire at the same time. In some applications (DirecTV AU9-S and AT-9), ranges of the lower B-band and 2250–3000 MHz, are used.

A brief reprieve in the effects of Metox was at hand in December 1942, when British codebreakers once again were able to break into the Naval Enigma and U-boat losses began to climb again due to intercepts revealing their positions and orders. This was combined with a key piece of false information planted by a captured British officer, who claimed their aircraft were equipped with a device to listen for the very weak signals given off by the Metox's intermediate frequency stage. This led to early 1943 orders from German Naval High Command to turn off the Metox, which allowed Mk. II to once again become effective for a time.

Typically only one of the new frequencies is desired, and the other signal is filtered out of the output of the mixer. The output signal will have an intensity proportional to the product of the amplitudes of the input signals. The most important and widely used application of the heterodyne technique is in the superheterodyne receiver (superhet), invented by U.S. engineer Edwin Howard Armstrong in 1918. In this circuit, the incoming radio frequency signal from the antenna is mixed with a signal from a local oscillator (LO) and converted by the heterodyne technique to a lower fixed frequency signal called the intermediate frequency (IF).

The number of pulses per frame gives the number of controllable channels available. The advantage of using PPM for this type of application is that the electronics required to decode the signal are extremely simple, which leads to small, light-weight receiver/decoder units. (Model aircraft require parts that are as lightweight as possible). Servos made for model radio control include some of the electronics required to convert the pulse to the motor position – the receiver is required to first extract the information from the received radio signal through its intermediate frequency section, then demultiplex the separate channels from the serial stream, and feed the control pulses to each servo.

SAT>IP is particularly aimed at satellite TV distribution in the home but can be applied to large multi-dwelling and hospitality reception systems too. Conventional satellite TV reception systems convert the received transmissions to an intermediate frequency (IF) for distribution via dedicated coaxial cables to one or more satellite tuners and demodulators in set-top boxes. SAT>IP allows the satellite TV distribution to share a data network and enables display and viewing of the signals on any multimedia IP device equipped with suitable software. Multiple SAT>IP servers and clients can operate on the same network with both free-to-air and encrypted pay-TV transmissions.

The Pye strip was such an advance on the EMI unit that the EF50 became a key strategic component. As a German invasion of the west loomed in 1940, the British contacted Philips and arranged a plan to remove the company's board of directors to the UK, along with 25,000 more EF50s and another 250,000 bases, onto which Mullard, Philip's UK subsidiary, could build complete tubes. A destroyer, , was dispatched to pick them up in May, and left the Netherlands only days before the German invasion on 15 May 1940. The Pye strip, and its 45 MHz intermediate frequency, would be re-used in many other wartime radar systems.

In place of the klystron, Marconi suggested using an existing magnetron that had proven itself in operation on their test rig at Bushy Hill in use since 1956. This system had been used during air exercises in 1956's Operation Stronghold, where it demonstrated its ability to track in rain, but did have problems with the display of "angels". The magnetron produced only 2 MW, significantly less than desired, but there did appear to be some development potential. To make MTI work with a magnetron, which does not use an intermediate frequency and is not stable, an emerging technique known as COHO was applied.

Subharmonic mixers (a particular form of harmonic mixer where the LO is provided at a sub multiple of the frequency to be mixed with the incoming signal) are often used in direct-digital, or zero IF, communications system in order to eliminate the unwanted effects of LO self- mixing which occurs in many fundamental frequency mixers. Used in frequency synthesizers and network analyzers. A variation on the subharmonic mixer exists that has two switching stages is used to improved mixer gain in a direct downconversion receiver. The first switching stage mixes a received RF signal to an intermediate frequency that is one-half the received RF signal frequency.

The first superheterodyne receiver built at Armstrong's Signal Corps laboratory in Paris during World War I. It is constructed in two sections, the mixer and local oscillator (left) and three IF amplification stages and a detector stage (right). The intermediate frequency was 75 kHz. The superheterodyne, invented in 1918 during World War I by Edwin Armstrong when he was in the Signal Corps, is the design used in almost all modern receivers, except a few specialized applications. It is a more complicated design than the other receivers above, and when it was invented required 6 - 9 vacuum tubes, putting it beyond the budget of most consumers, so it was initially used mainly in commercial and military communication stations.

A major one was that the planned S-band magnetron, the BM 735, was only available in small numbers and would rarely work when pushed beyond 1 MW of its 2 MW rated power. Additionally, the slip-ring system for feeding radio frequency power to the antenna also continued to be a problem. This led to experiments with slip- rings that fed the intermediate frequency (IF) instead, with the magnetron transmitters and first stages of the superheterodyne receivers on the rotating platform. In June 1951, with these problems ongoing, it was decided to move ahead with all the parts that did work in order to get a production system as soon as possible.

Another problem is that MTI requires the pulses to be stored for the length of the pulse repetition frequency. Analogue devices capable of cleanly storing high-frequency signals in the microwave region are not common, so here the solution was to use a much lower frequency intermediate frequency (IF) signal as the basis for the pulse, feeding this into a frequency multiplier before amplification by a device like a klystron. On reception, the signal path is reversed, producing an output similar to the original IF. This lower frequency can be stored in a number of analog devices like an analog delay line. This concept works fine for radars using amplifiers like a klystron, which amplify an input signal.

Basic heptode-based self-oscillating pentagrid converter circuits. Top: Indirectly-heated variant Bottom: Directly-heated variant, which requires the cathode to be grounded Grids of a 12SA7GT pentagrid converter, showing all five grids The pentagrid converter is a type of radio receiving valve (vacuum tube) with five grids used as the frequency mixer stage of a superheterodyne radio receiver. The pentagrid was part of a line of development of valves that were able to take an incoming RF signal and change its frequency to a fixed intermediate frequency, which was then amplified and detected in the remainder of the receiver circuitry. The device was generically referred to as a frequency changer or just mixer.

This problem becomes more complicated when several receivers use several dishes or several LNBs mounted in a single dish are aimed at different satellites. The set-top box selects the channel desired by the user by filtering that channel from the multiple channels received from the satellite, converts the signal to a lower intermediate frequency, decrypts the encrypted signal, demodulates the radio signal and sends the resulting video signal to the television through a cable. To decrypt the signal the receiver box must be "activated" by the satellite company. If the customer fails to pay his monthly bill the box is "deactivated" by a signal from the company, and the system will not work until the company reactivates it.

In wireless telegraphy (WT) and amateur radio, sidetone is the audible indication of a continuous wave (CW) signal as the operator sends Morse Code. As in telephony, sidetone serves as feedback to the operator that what they are sending is what is intended. It is designed to mimic the tone generated by a typical radio receiver when a CW signal is converted to the intermediate frequency (IF), then mixed with the Beat frequency oscillator (BFO) frequency to generate a difference frequency, which is audible over the radio receiver loudspeaker or headphones. Sidetone is also used on voice radio equipment to give the radio operator confidence that they are transmitting over the radio.

On 7 March, U-156 was attacked in a similar fashion, and radioed in that they believed a new radar was being used. In spite of this early warning of a new system, German efforts were hampered by one of the most effective bits of misinformation of the war. A Coastal Command captain who had been captured after crashing told a plausible story, apparently entirely of his own creation, that threw the Germans off the scent for months. He stated that they no longer used Mk. II for the initial detection, and instead used a new receiver that listened for the slight leakage of the intermediate frequency used in the Metox's tuner.

Following 2nd stage amplification, conditioning and filtering the astronomical signal is mixed with a Local Oscillator signal at 1.53 GHz to give a 170 MHz Intermediate Frequency (IF) bandwidth centred at 755 GHz. This IF is then re-routed to the backends in the control room some 5 metres below via a cable wrap. A phasecal signal is also injected to the IF module to remove phase errors. This band is primarily used for atmospheric calibration of VLBI observations?¿. CH-Band :The C-H band is a dual polarisation channel that covers from 3.22 – 3.39 GHzThe receiver consists of a choke ring axial corrugated horn that was designed by the Antenna Group at the Technical University of Madrid.

April 17, 2009. On 99.1, the station had to maintain lower power and a slightly directional antenna due partly to WDEN- FM 99.1 in Macon, which often caused RF interference with the station, particularly early on calm mornings due to overnight temperature inversions that enhance radio propagation. It was required to run at less than 100 watts due to the proximity of WRAS FM 88.5, since the intermediate frequency (IF) of 10.7 MHz used in radio tuners puts the station's IF at 88.4, overlapping the lower half of 88.5's channel. For its initial two weeks on 99.1, the station was required to run at half power due to testing required for all new directional antenna installations.

The development of microwave technology during the 1930s run up to World War 2 for use in military radar led to the resurrection of the point contact crystal detector. Microwave radar receivers required a nonlinear device that could act as a mixer, to mix the incoming microwave signal with a local oscillator signal, to shift the microwave signal down to a lower intermediate frequency (IF) at which it could be amplified. The vacuum tubes used as mixers at lower frequencies in superheterodyne receivers could not function at microwave frequencies due to excessive capacitance. In the mid-1930s George Southworth at Bell Labs, working on this problem, bought an old cat whisker detector and found it worked at microwave frequencies.

McNicol, Donald (1946) Radio's Conquest of Space, p. 272-278 However, by the 1930s the "superhet" had replaced all the other receiver types above. In the superheterodyne, the "heterodyne" technique invented by Reginald Fessenden is used to shift the frequency of the radio signal down to a lower "intermediate frequency" (IF), before it is processed. Its operation and advantages over the other radio designs in this section are described above in The superheterodyne design By the 1940s the superheterodyne AM broadcast receiver was refined into a cheap-to-manufacture design called the "All American Five", because it only used five vacuum tubes: usually a converter (mixer/local oscillator), an IF amplifier, a detector/audio amplifier, audio power amplifier, and a rectifier.

It was known from the start of the LORAN project that the same CRT displays that showed the LORAN pulses could, when suitably magnified, also show the individual waves of the intermediate frequency. This meant that pulse-matching could be used to get a rough fix, and then the operator could gain additional timing accuracy by lining up the individual waves within the pulse, like Decca. This could either be used to greatly increase the accuracy of LORAN, or alternately, offer similar accuracy using much lower carrier frequencies, and thus greatly extend the effective range. This would require the transmitter stations to be synchronized both in time and phase, but much of this problem had already been solved by Decca engineers.

The most common application of the reflex circuit in the 1920s was in inexpensive single tube receivers, because many consumers could not afford more than one vacuum tube, and the reflex circuit got the most out of a single tube, it was equivalent to a two-tube set. During this period the demodulator was usually a carborundum point contact diode, but sometimes a vacuum tube grid-leak detector. However multitube receivers like the TRF and superheterodyne were also made with some of their amplifier stages "reflexed". The reflex principle was used in compact Australian superheterodyne radio receivers of the late 1940s and very early 1950s; the intermediate frequency amplifier stage was also the first audio frequency stage using a reflex arrangement.

Signals to be uplinked to a spacecraft must first be extracted from ground network packets, encoded to baseband, and modulated, typically onto an intermediate frequency (IF) carrier, before being up-converted to the assigned radio frequency (RF) band. The RF signal is then amplified to high power and carried via waveguide to an antenna for transmission. In colder climates, electric heaters or hot air blowers may be necessary to prevent ice or snow buildup on the parabolic dish. Received ("downlinked") signals are passed through a low-noise amplifier (often located in the antenna hub to minimize the distance the signal must travel) before being down-converted to IF; these two functions may be combined in a low-noise block downconverter.

After this success, Bowen was granted two Avro Anson patrol aircraft, K6260 and K8758, along with five pilots stationed at Martlesham to test this ship- detection role. Early tests demonstrated a problem with noise from the ignition system interfering with the receiver, but this was soon resolved by fitters at the Royal Aircraft Establishment (RAE). Meanwhile, Hibberd had successfully built a new push–pull amplifier using two of the same tubes but working in the 1.25-meter band, an upper-VHF band (around 220 MHz); below 1.25 m the sensitivity dropped off sharply. Gerald Touch, originally from the Clarendon Laboratory, converted the EMI receiver to this wavelength by using the existing set as the intermediate frequency (IF) stage of a superheterodyne circuit.

Transverters are most commonly used in amateur radio to convert radio transceivers designed for use on the HF or VHF bands to operate on even higher frequency (microwave) bands. A transceiver used in this fashion is referred to as an IF radio, indicating that it connects into the "intermediate frequency" electronics in the chain of transceiver stages. Common transceiver/transverter combinations include transverters for 50 MHz, 70 MHz, 144 MHz, 222 MHz, and 432 MHz designed for use with 28 MHz IF radios, and transverters for 50 MHz, 902 MHz, 1296 MHz, 2304 MHz, 3456 MHz, 5706 MHz, and 10368 MHz designed for use with 144 MHz IF radios. Some transverters include transmit/receive switching built into the design, whereas other units require external switching.

MTI is accomplished by comparing an incoming signal from the current radar pulse with the last one sent, and looking for changes in frequency due to the Doppler shift. This requires the last pulse to be stored so it can be compared with the current one, which is difficult to do at microwave frequencies. The simplest solution is to use a much lower intermediate frequency (IF) as the basis for the pulse and then electronically multiply its frequency before sending, dividing it again on reception for storage. This requires the IF to be extremely stable, which makes it difficult to accomplish with a magnetron as these devices output a slightly different signal, in both frequency and phase, with every pulse.

The heterodyne receiver, which uses a superconducting-insulator-superconducting (SIS) Josephson junction as the mixer, is the two-backshort design of Kerr (Pan et al. 1983). A scalar feed couples the microwave signal to the receiver, where it is mixed with a local oscillator (LO) signal to produce a 1.4 GHz intermediate frequency (IF) signal that is further amplified with a low-noise high electron mobility field effect transistor (HEMT FET) amplifier, and passed to the IF section of the receiver. The IF section further amplifies the signal and heterodynes it down to 150 MHz, passing a bandwidth of 200 MHz to the spectrometer. The LO signal is generated by a Gunn diode oscillator whose frequency is controlled via a phase-lock loop system by a computer-controlled frequency synthesizer.

Since the resonant frequency of a SAW device is set by the mechanical properties of the crystal, it does not drift as much as a simple LC oscillator, where conditions such as capacitor performance and battery voltage will vary substantially with temperature and age. SAW filters are also often used in radio receivers, as they can have precisely determined and narrow passbands. This is helpful in applications where a single antenna must be shared between a transmitter and a receiver operating at closely spaced frequencies. SAW filters are also frequently used in television receivers, for extracting subcarriers from the signal; until the analog switchoff, the extraction of digital audio subcarriers from the intermediate frequency strip of a television receiver or video recorder was one of the main markets for SAW filters.

In a simple superheterodyne receiver, the incoming radio frequency signal (at frequency f_{IN}) from the antenna is mixed with the VFO output signal tuned to f_{LO}, producing an intermediate frequency (IF) signal that can be processed downstream to extract the modulated information. Depending on the receiver design, the IF signal frequency is chosen to be either the sum of the two frequencies at the mixer inputs (up-conversion), f_{IN}+f_{LO} or more commonly, the difference frequency (down-conversion), f_{IN}-f_{LO}. In addition to the desired IF signal and its unwanted image (the mixing product of opposite sign above), the mixer output will also contain the two original frequencies, f_{IN} and f_{LO} and various harmonic combinations of the input signals. These undesired signals are rejected by the IF filter.

Central to these designs was concept of block downconversion of a range of frequencies to a lower, more easily handled IF. LNB. The advantages of using an LNB are that cheaper cable can be used to connect the indoor receiver to the satellite television dish and LNB, and that the technology for handling the signal at L-band and UHF was far cheaper than that for handling the signal at C-band frequencies. The shift to cheaper technology from the hardline and N-connectors of the early C-band systems to the cheaper and simpler 75-ohm cable and F-connectors allowed the early satellite television receivers to use, what were in reality, modified UHF television tuners which selected the satellite television channel for down conversion to a lower intermediate frequency centered on 70 MHz, where it was demodulated.

One can incoherently add the magnitudes of a time series of N independent pulses to obtain a improvement in the signal to noise on the amplitude, but at the expense of losing the phase information. Instead coherent addition (adding the complex magnitude and phase) of multiple pulse waveforms would improve the signal to noise by a factor of N, not its square root, and preserve the phase information. The practical limitation is adjacent pulses from typical lasers have a minute frequency drift that translates to a large random phase shift in any long distance return signal, and thus just like the case for spatially scrambled-phase pixels, destructively interfere when added coherently. However, coherent addition of multiple pulses is possible with advanced laser systems that narrow the frequency drift far below the difference frequency (intermediate frequency).

One also needs a radio signal detector that can operate at equally high frequencies, cables capable of carrying that signal to the antenna efficiently, and a host of other developments. The Navy was in a particularly good position to take advantage of the magnetron, as part of their Experimental Department was the Valve Laboratory. In 1939, the Valve Laboratory was put in charge of the Committee for the Coordination of Valve Development (CDV), leading development of new valve technology for all of the UK's armed forces. The Valve Laboratory led development of the tunable reflex klystron that provided the needed intermediate frequency signal for a superheterodyne receiver that operated at microwave frequencies, while the Telecommunications Research Establishment (TRE), the Air Ministry's research arm, introduced a silicon-tungsten crystal detector that generated the appropriate high-frequency signals for the reflex klystron.

The infrared seeker does not use IR filters to reject decoys, although there is a degree of protection provided by the use of intermediate frequency seeker scanning pattern. Each launcher is equipped with an optical director than can be used instead of the radar in a high ECM environment or if the radar is not operational; additionally the vehicle can be mounted with one or two 12.7 mm calibre heavy machine guns, for self-defense in frontal forward areas against ground threats and close-in(<500 m) incoming air threats. The system can be set up in approximately 30 minutes, and the launcher reload time for all four missiles is around three minutes. SAM-1C upgraded missile use a phased array active radar seeker, with the capability of receiving mid-course guidance updates from the Fire Control Systems vehicle.

An intermediate frequency was first used in the superheterodyne radio receiver, invented by American scientist Major Edwin Armstrong in 1918, during World War I. A member of the Signal Corps, Armstrong was building radio direction finding equipment to track German military signals at the then-very high frequencies of 500 to 3500 kHz. The triode vacuum tube amplifiers of the day would not amplify stably above 500 kHz, however, it was easy to get them to oscillate above that frequency. Armstrong's solution was to set up an oscillator tube that would create a frequency near the incoming signal, and mix it with the incoming signal in a 'mixer' tube, creating a 'heterodyne' or signal at the lower difference frequency, where it could be amplified easily. For example, to pick up a signal at 1500 kHz the local oscillator would be tuned to 1450 kHz.

The LNB amplifies the signals and downconverts them to a lower block of intermediate frequencies (IF), usually in the L-band. The original C-band satellite television systems used a low-noise amplifier (LNA) connected to the feedhorn at the focal point of the dish. The amplified signal, still at the higher microwave frequencies, had to be fed via very expensive low-loss 50-ohm impedance gas filled hardline coaxial cable with relatively complex N-connectors to an indoor receiver or, in other designs, a downconverter (a mixer and a voltage-tuned oscillator with some filter circuitry) for downconversion to an intermediate frequency. The channel selection was controlled typically by a voltage tuned oscillator with the tuning voltage being fed via a separate cable to the headend, but this design evolved. Designs for microstrip-based converters for amateur radio frequencies were adapted for the 4 GHz C-band.

In early 1944, the UK began to deploy its Type 650 transmitter, which employed a different approach. This system jammed the Straßburg receiver's intermediate frequency section, which operated at a 3 MHz frequency and appears to have been quite successful, especially because the operator did not have to attempt to find which of the 18 Kehl-Straßburg command frequencies were in use and then manually tune the jamming transmitter to one of them. The Type 650 automatically defeated the receiver, regardless which radio frequency had been selected for an individual missile, be it Fritz X or Hs 293. Following several intelligence coups, including a capture of an intact Hs 293 at Anzio and recovery of important Kehl transmitter components from a crashed Heinkel He 177 on Corsica, the Allies were able to develop far more effective countermeasures in time for the invasion of Normandy and Operation Dragoon.

In some modulation systems based on AM, a lower transmitter power is required through partial or total elimination of the carrier component, however receivers for these signals are more complex because they must provide a precise carrier frequency reference signal (usually as shifted to the intermediate frequency) from a greatly reduced "pilot" carrier (in reduced-carrier transmission or DSB-RC) to use in the demodulation process. Even with the carrier totally eliminated in double-sideband suppressed-carrier transmission, carrier regeneration is possible using a Costas phase-locked loop. This does not work for single- sideband suppressed-carrier transmission (SSB-SC), leading to the characteristic "Donald Duck" sound from such receivers when slightly detuned. Single-sideband AM is nevertheless used widely in amateur radio and other voice communications because it has power and bandwidth efficiency (cutting the RF bandwidth in half compared to standard AM).

It is possible for the unwanted signal to enter an Intermediate frequency stage, and if it falls within the passband of the stage, it can cause an unwanted effect. In an AM system, it is possible that the unwanted signal will be amplified by the linear stage and appear finally to the detector as if it were a sideband of the carrier, it is possible sometimes for harmonics of an HF transmitter generated within a TV set to enter the video IF (which is at about 30 MHz). These harmonics which enter the TV IF could give similar herring bone pattern effects to those seen when harmonics of the HF transmitter are generated in the front end. In FM systems where the IF stage gain is very high and the stage is designed to be linear, it is likely that if the unwanted signal is at least 10 dB weaker than the wanted signal that the capture effect will result in the receiver ignoring the unwanted signal.

RG-59 is not recommended for this application as it is not technically designed to carry frequencies above 950 MHz, but will work in many circumstances, depending on the quality of the coaxial wire. The shift to more affordable technology from the 50ohm impedance cable and N-connectors of the early C-band systems to the cheaper 75ohm technology and F-connectors allowed the early satellite television receivers to use, what were in reality, modified UHF television tuners which selected the satellite television channel for down conversion to another lower intermediate frequency centered on 70 MHz where it was demodulated. An LNB can only handle a single receiver. This is due to the fact that the LNB is mapping two different circular polarisations – right hand and left hand – and in the case of the Ku-band two different reception bands – lower and upper – to one and the same frequency band on the cable, and is a practical problem for home satellite reception.

Another, very similar application of the bi-grid valve was as a self oscillating frequency mixer in early superhet receivers One control grid carried the incoming RF signal, while the other was connected into an oscillator circuit which generated the local oscillation within the same valve. Since the anode current of the bi-grid valve was proportional both to the signal on the first grid, and also to the oscillator voltage on the second grid, the required multiplication of the two signals was achieved, and the intermediate frequency signal appeared in an appropriately tuned circuit connected to the anode. In all of the applications mentioned, the bi-grid tetrode acted as an analogue multiplier (analog multiplier) which multiplied together the signals applied to the two grids. The super-sonic heterodyne (superhet) receiver principle was invented in France by Lucien Levy in 1917 (p 66), though credit is usually also given to Edwin Armstrong.

A product detector is a type of demodulator used for AM and SSB signals, where the original carrier signal is removed by multiplying the received signal with a signal at the carrier frequency (or near to it). Rather than converting the envelope of the signal into the decoded waveform by rectification as an envelope detector would, the product detector takes the product of the modulated signal and a local oscillator, hence the name. By heterodyning, the received signal is mixed (in some type of nonlinear device) with a signal from the local oscillator, to give sum and difference frequencies to the signals being mixed, just as a first mixer stage in a superhet would produce an intermediate frequency; the beat frequency in this case, the low frequency modulating signal is recovered and the unwanted high frequencies filtered out from the output of the product detector. Because the sidebands of an amplitude-modulated signal contain all the information in the carrier displaced from the center by a function of their frequency, a product detector simply mixes the sidebands down into the audible range so that the original audio may be heard.

In addition to the controversial practice of converting the HD Radio-only secondary channels of a primary station into analog FM in areas where the primary station's signal can already readily be received, translators can also be used in a more traditional manner to extend the range of the full content of the primary station, including the unmodified main signal and any HD radio sub-channels, in areas where the station has poor coverage or reception, as is done at K202BD in Manti, Utah, which rebroadcasts both the analog and digital signals of KUER from Salt Lake City. In order to do this, HD Radio may be passed along from the main station via a "bent pipe" setup, where the translator simply makes a frequency shift of the entire channel, often by heterodyning it through the use of an intermediate frequency. This may require an increase in bandwidth in both the amplifier and radio antenna if they are too narrowband to pass the wider signal, meaning one or both would have to be replaced. Baseband translators which use a separate receiver and transmitter require an HD Radio transmitter, just as does the main station.