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GEORGE K9GDT Manual

40m cw/ssb
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K9GDT
K9GDT
40m CW/SSB
40m
CW/SSB
Receiver
Receiver

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Summary of Contents for GEORGE K9GDT

  • Page 1 K9GDT K9GDT 40m CW/SSB CW/SSB Receiver Receiver...

  • Page 2: Table Of Contents

    3-7 Crystal Filter - IF Amplifier - AGC Module ..................3-8 Audio Processing Board ......................... 3-9 Display Module ..........................Illustrations Figure 1-1 The K9GDT 40m Receiver ..................... Figure 2-1 Receiver Block Diagram ......................Figure 2-2 Front Panel Controls ......................Figure 2-3 Rear Panel Controls and Connections ..................

  • Page 3: Description Of Receiver

    Figure 1-1 K9GDT 40m Receiver 1-1 Description The K9GDT 40m receiver is a solid state receiver that The PASSBAND tuning control is an operating aid offers a very high level of performance for the 40m useful in reducing or eliminating interfering signals.

  • Page 4: Introduction

    Introduction 1-2 Specifications Frequency Coverage Spurious Response < 65 dB 40m Amateur Radio Band 2.1KHz - Less than 0.4 µV Sensitivity Frequency Readout 10ppm ±100Hz for 10 dB S+N Accuracy 400Hz - Less than 0.15 µV for 10 dB S+N 2.1KHz @ −6 dB Selectivity Frequency Stability...

  • Page 5: Circuit Description

    Introduction Circuit Description K9GDT 40m CW/SSB Receiver 3.395 MHz Post I.F. Low Noise 8 pole 500Hz Switched A.F. Product 400Hz Filter First Mixer Post Mixer Crystal Filters Filter I.F. Capacitor Tuneable AF Amplifier Detector 7-7.3 MHz SBL-1 Amplifier L. P. Filter 3.5W 8 Ω...

  • Page 6: Crystal Filter - If Amplifier - Agc Module

    Circuit Description 2-3 Crystal Filter - IF Amplifier - AGC Module when a strong signal appears while preventing most Crystal Filters pops and noises from “hanging” the AGC system. The received signal is fed to this module and routed to one of two eight-pole crystal filters by steering diodes.

  • Page 7: 400Hz Noise Filter/ Product Detector Module

    Circuit Description 2-4 400Hz Noise Filter/Product Detector 400Hz Noise Filter Product Detector A sample of the IF amplifier’s output is fed to the The received signal is then routed to the modulating 400Hz noise filter/product detector for conversion to signal input port of a Motorola MC1496-P balanced audio.

  • Page 8: Vfo

    Circuit Description 2-6 VFO The VFO functions as the main tuning element by variable capacitor driven by a zero-backlash flywheel supplying a 6-6.3Mhz signal to the LO - Passband weighted 50:1 gear reduction drive. Generator module. The signal is produced by a temperature compensated series-tuned Colpitts JFET The oscillator stage is followed by a two transistor oscillator with 6.3 volt zener diode regulation.

  • Page 9: Power Supply

    Circuit Description 2-10 Power Supply The power supply consists of four regulated outputs of the post-mixer amplifier. The AF power amplifier is +5, +12, +15, and +20 volts. The +5 volt output is used operated from the +20 volt section, which is a National to power the TTL and CMOS chips used in the Semiconductor LM338AK 4 amp voltage regulator.

  • Page 10: Figure 2-4 Interior Views - Module Locations

    Circuit Description Figure 2-4 Interior Views - Module Locations Bandpass Filter AF Power Amplifier Power Supply Display Module Crystal Filters AF Processor Board IF Amplifier/ AGC Mixer - Post Mixer Amplifier Module Top View LO-Passband Generator Module Audio Processing Board BFO Generator Bandpass Filter Power Supply...

  • Page 11: Alignment And Calibration

    Circuit Description Alignment and Calibration 3-1 Required Test Equipment • A DC voltmeter whose measurement uncertainty is better than 0.5% of reading. • An oscilloscope with a bandwidth of at least 30Mhz. • A frequency counter with 30MHz capability, 10Hz resolution, and a measurement uncertainty of 10 ppm. •...

  • Page 12: Bfo Generator

    Circuit Description 3-4 BFO Generator 1MHz Offset Oscillator Adjustment BFO Amplifier Adjustment Connect an oscilloscope to the 1MHz oscillator test Center the front panel PASSBAND control. Use an point and adjust L1 for maximum output. oscilloscope to observe the signal at the RCA jack labeled DISP.

  • Page 13: Crystal Filter - If Amplifier - Agc Module

    Alignment and Calibration 3-7 Crystal Filter - IF Amplifier - AGC Module AGC Bias Adjustment Tune in the generator’s signal and adjust C1, C2, & Rotate the front panel AGC switch to “F” and turn the L1 for maximum deflection on the signal strength front panel RF GAIN control fully clockwise.

  • Page 14: Audio Processing Board

    Alignment and Calibration 3-8 Audio Processing Board Notch Depth Adjustment until all distortion products are inaudible. Rotate R2 Connect the signal generator the receiver and adjust for two additional turns. Turn off the notch filter and it’s output for a 500µV signal at 7.05MHz. Tune the verify the presence of the 600Hz tone.

  • Page 15: Display Module

    Reconnect the signal generator and adjust it’s output to 30 mV at 7.05MHz. Turn the AGC switch to “F” Tune the K9GDT receiver for a display reading of and adjust the PASSBAND control for maximum 7125.0KHz. Next, tune the test communications receiver to 7125KHz and pick up the signal generated reading on the S-meter.

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