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131 Cards in this Set
- Front
- Back
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GRT VHF frequency range
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116-149.975 MHz |
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GRT UHF frequency range |
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GRT power output |
10 to 12.5 W
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GRT modulation |
90% +- 10% |
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GRT audio frequency response
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300-6000 hz modulation within +1 or -2 db |
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GRT thermal protection |
actuated at 85 degrees |
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Output of GRT A1 goes to
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Filter amplifier/detector A4 |
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Accuracy and stability of the ________ determines the accuracy and stability of the transmitter set
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Oscillator synthesizer
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Two sections of the GRT filter amp/detector A4
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Filtering section and metering section |
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The output of the GRT multiplier A9
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Operating frequency |
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Components of the GRT APC circuit
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Power detector DC1, power amplifier A10, control RF/modulator A6 |
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Power detector DC1 develops these two voltages in GRT
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Forward power and reflected power |
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Controls the gain of the GRT power amplifier A10 |
APC voltage |
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Maintains constant audio output amplitude with varying audio amplitude input
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Audio amp compressor A1 |
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If VSWR exceeds __, the LPA is bypassed to prevent damage
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3:1 |
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Circuits on LPA that allow for 60 second warm-up |
AC control circuits |
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FWD and RVS go to A6 where they develop ____
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APC voltage |
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Two functions of the LPA tune/operate switch
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Decreases the exciter output to less than 10W and prevents the E/L relay from energizing
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When GRR operating frequency is changed, the ____ changes
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Local oscillator frequency |
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Section in GRR where the majority of amplification takes place
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IF section |
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Difference between mixer and converter
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Mixer requires injection frequency, converter generates its own |
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Image frequency |
Undesired signal that produces the correct IF in the mixer |
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Image frequency = ____ +- ____ |
Operating frequency +- 2(IF)
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Why the IF is amplified once more before going to the detector
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IF is too weak to be demodulated |
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Requirements for demodulation |
Sensitivity, nonlinearity, RF carrier, filtering |
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Advantages of diode detectors |
Small and give high-fidelity detection for large signals |
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Disadvantages of diode detectors |
No power gain, selectivity is affected by loading of the tank |
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VHF GRR number of channels
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680 using the 50 kHz filter, 1360 using the 25 kHz filter |
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UHF GRR number of channels |
3500 using the 50 kHz filter, 7000 using the 25kHz filter |
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VHF GRT number of channels |
2720 |
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UHF GRT number of channels |
7000 |
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The most selective filter in the GRR |
FL1 |
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GRR Intermediate frequency
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20.6 MHz |
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IF amplifier/detector A6 minimum gain
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94 dB |
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GRC frequency ranges |
7000 channels from 225 to 399.975 on UHF, 1440 channels from 116 to 151.975 |
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VHF GRC output power |
25W |
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UHF GRC output power |
20W |
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GRC receive audio frequency response |
300 to 3000 hz, 16 to 25000 hz for wideband |
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GRC transmit audio frequency response
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300 hz to 6000 hz, 16 to 25000 hz for data |
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GRC contains separate receive and transmit ____ and ____ |
Audio amplifiers and filters
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Types of keying in the GRC |
Ground, voltage, current and audio
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Key 1 is ______, Key 2 is _______
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Fast attack slow release, slow attack fast release |
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Purpose of the time delay between key 1 and key 2
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So the receiver is deactivated before the RF Is amplified, so the receive circuits aren't damaged |
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Determine the GRC audio frequency response
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High pass and low pass filters |
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Keeps the GRC mod% constant |
Compression amplifier |
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Produces the GRC carrier during transmit and injection frequency during receive
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Frequency synthesizer A2 |
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Eliminates harmonics generated in the GRC A8 module |
RF filter |
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Provides preselection and eliminates image frequencies in GRC receive |
RF filter |
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First mixer in the GRC passes ___ |
30 MHz |
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Second mixer in the GRC passes ___ |
10.7 MHz |
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Only part of the GRC not mounted on the chassis |
Radio set control
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GRC power supply consists of ______
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One switching regulator and several series regulators |
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Produced by the GRC switching regulator
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26 VDC |
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GRC power supplies |
A5 and A6 |
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Not included in the TRC-176 |
TSEC/KY-57 encryption device` |
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Components of the TRC-176
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RT, radio set control, audio amp, headset, handset, antenna, interconnecting cables, carrying case |
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What VRC-83 is designed for
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Vehicle operations |
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VRC-83 output power |
30W |
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Components of PRC-113
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RT, battery box with two lithium nonrechargeable or two NiCad rechargeable batteries, antenna, handset |
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Frequency range of URC |
8360 channels spaced across VHF and UHF |
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Modulation of URC
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87% +- 7.5% |
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URC output power |
2 or 10 W |
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Accomplishes tuning of the main receiver on the RT |
Data converter A1 |
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Frequency the RT guard receiver A5 is tuned to |
Guard frequency 243.00 MHz |
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Where the URC carrier frequency comes from |
Synthesizer |
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Contained in the modulator A3 and the transmitter A2 |
Transmission circuitry |
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Four voltages provided by the power regulator
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6.3 VDC, -29 VDC, 13.5 VDC, 12 VDC |
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Escape of magnetic and electric fields from around transmission lines |
Radiation and induction loss |
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How to minimize induction loss |
Using standoff insulators to separate conductors
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How to minimize leakage loss
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Using very high-resistance dielectric materials |
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How to minimize skin loss
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Increasing the diameter of the conductor |
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Major power loss of flexible coaxial cables |
Dielectric and skin effect |
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Why rigid coaxial cables have very little radiation |
Energy is confined between the two conductors |
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What is characteristic impedance |
Ratio of voltage to current on a transmission line |
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What is impedance |
Opposition to alternating current |
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Cutoff frequency |
Highest frequency that passes down the line |
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Formula to determine wavelength
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300 / frequency in MHz |
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Formula to determine electrical length
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Physical length / wavelength |
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Nonresonant transmission line |
Transmission line having no reflected waves |
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What is VSWR |
Ratio of maximum voltage on a line to minimum voltage |
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What does it mean if VSWR is 1:1 |
The impedance matches |
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What is the standing wave of a line |
Voltage equal to the vector sum of the forward and reverse signals |
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With an open termination, voltage reflects ____ and current reflects ____ with the incident wave |
In phase, 180 degrees out of phase |
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With a shorted termination, voltage reflects _____ and current reflects _____ with the incident wave |
180 degrees out of phase, in phase |
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Define impedance |
The opposition to AC |
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Purpose of a balun |
Matching impedance between a cable and an antenna |
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Two components of a space wave |
Direct wave and ground reflected wave |
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Antenna reciprocity |
Ability of an antenna to transmit and receive equally well |
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An antenna is a transducer because _______ |
It converts RF energy into electric and magnetic fields of force |
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What is an isotropic antenna |
Theoretically perfect antenna that transmits equally well in all directions |
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What is dBi? |
Decibels in reference to an isotropic antenna |
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Polarization and frequency range of AT-197 |
Vertical, 225-400 MHz |
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Advantage of an AT-197 |
Lightweight and versatile mounting hardware |
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Advantage of AS-1181 |
Fiberglass radome enclosure that protects it from weather and rough handling, suitable for deployed environments |
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Polarization and frequency range of AS-1181 antenna |
Vertical, 100-156 MHz |
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Polarization and frequency range of AS-1097 antenna |
Vertical, 225-400 MHz |
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Advantage of AS-1097 antenna |
Provides 4 dBi of gain |
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Polarization and frequency range of AS-3472 and AS-3473 antennas |
Vertical, 115-156 MHz |
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Advantage of AS-3472/3473 antennas |
4 dBi gain, prevents cross-talk interference from adjacent channels |
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Advantages of dipole colinear array antennas |
Lightweight, durable and available in many specifications |
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Length of transmission unit in asynchronous transfer mode |
One character |
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How does receiving device determine if it has a correct character |
Even number of 1 bits |
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Part of asynchronous transfer mode that tells receiving device that a character is coming |
Parity bit |
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What VRC checks each incoming character for |
Parity bit |
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Character that LRC uses to determine if transmission was error-free |
Horizontal line |
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Divides the sum in checksum error detection |
255 |
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How CRC determines the dividend when computing the BCC |
Treats the ones and zeroes in the frame address, control and information fields as a single binary number |
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How effective CRC is at detecting errors in most applications |
99% |
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How ARQ works |
Receiver resends the request if it finds an error in received frame |
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Transmitters function when using forward error control |
Send multiple copies of the same message |
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Receiver's function in forward error control |
Compare all copies and reconstruct message from good portions of the message |
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Sets transmitter audio frequency response |
Filter portion of A4 |
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Where wideband audio is applied in the GRT |
Buffer modulator A5 |
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Where the carrier go from the multiplier in the GRT |
A10 |
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Why is RF removed from the E/L relay when it energizes |
To protect contacts from arcing |
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Lower and upper limits of squelch output in the receiver |
3 uV, 50 uV |
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What happens to the DC portion of the receiver detector output |
Amplified and processed into AGC voltage |
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Receiver sensitivity |
100 mW into a 600 ohm load |
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What is the receiver A6 |
IF amplifier |
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Where RF modulates in the GRC |
RF preamp/MOD section of A8 |
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Formula to find D/A voltage in the GRC |
(4 * frequency - 536) / 9 |
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Where first and second IF are produced in the GRC |
IF section
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Which version of GRC is more sensitive |
VHF |
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GRC version with 90 percent duty cycle transmit |
UHF |
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Version of GRC with wideband filter |
UHF |
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Sensitivity of VHF GRC |
1.5 uV |
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Sensitivity of UHF GRC |
3 uV |
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How overheating is controlled in the RT |
Low power amp switches to 2W mode |
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Circuits in the RT assembly |
Power amps, RF switching networks, low pass filters, thermal detector, reflected power sensor |
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Functions of the RT A1 |
Keyboard decoding, LCD display control, mode control, synthesizer freqency control |
