Review: Gonset G-76 Transceiver

Discussion in 'Amateur Radio Equipment Reviews' started by N8FVJ, Mar 14, 2020.

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  1. N8FVJ

    N8FVJ Ham Member QRZ Page

    The Gonset G-76 is an AM transceiver with a BFO for SSB receive only. As a low cost alternate vs a Johnson Ranger & receiver such as a Hamarlund HQ-145. The Gonset is more of a separate receiver and transmitter in one case sharing a transmit/receive relay only. The Gonset receiver is quite good and is double conversion. It is a better receiver vs a Hallicrafters S-108. The transmitter is high level modulated using a pair of 6DQ6 into a 6DQ5 RF amplifier operating in Class C for high efficiency. It produces 50 watts carrier output.

    A few issues exist. One is the 750pF capacitor in the VFO should be replaced with three 220pF NPO and a 75pF N750 to stabilize the frequency drift. (my G-76 has little drift for unknown reasons). The second issue is radios with the 12AQ5 clamp tube require a few parts removed to reduce the wide IF bandwidth to 3.2kHz with a 5 to 1 skirt ratio. The two I.F.'s next to the two 12BA6 have a 5pF and 100K resistor on each I.F. can. Leave the 100K resistor in place on side that cponnects to the tube grid. On the opposite side of the I.F. cans remove the 100K resistor. Wired across the I.F. (input to output) is a 5pF capacitor, remove it. Older transceivers without the 12AQ5 clamp tube do not need this modification. Finally on the 12AX7 tube grid to ground is a .01uF cap. Replace it with a 100pF capacitor to have response on receive and transmit below 200Hz. Early transceivers without the clamp tube already have the 100pF in place. As a small improvement, place a .01 capacitor across the two 12BA6 12 volt filament.

    Used Gonset G-76 costs about $75 to $100. The power supply costs the same, but not many are with the G-76. You can use a Drake AC-3 or AC-4 power supply with a new matching connector that fits the G-76 transceiver. The Heathkit HP-23 makes too high voltage for the Gonset. Have fun on AM.
     
    PU2OZT likes this.
  2. N8FVJ

    N8FVJ Ham Member QRZ Page

    Do note if using a non Gonset matching power supply, a high voltage relay must be installed in the power supply to disconnect the 600 volts DC from the transmitter during receive. A relay rated 250 volts AC & 250 volts DC will handle the 600 volts DC. Wire the double pole relay with the 600 volt DC in & out to the relay normally open contacts. Then wire the toggle side contacts together. This doubles the relay contact spacing when the relay is not energized. You can place a .01uF @ 1.5KV capacitor across each contact to reduce arcing. You can use a half wave (single diode) & 1000uF capacitor off of the 12.6 volt filament power to produce DC for a 12 volt relay coil.
     
    Last edited: Mar 16, 2020
    PU2OZT likes this.

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