Homebrew 80m 5W SSB/CW transceiver with 2 x AD831 active mixers and 6 pole quartz ladder filter. Also "bullet proof" J. It has "built in" frequency counter & voltage meter, 6dB & 12dB receiving attenuator, 2W AF amplifier as well as SWR/PWR meter.
The 80m SSB & CW transceiver design is based on an already proven concept used in ATLAS amateur transistorised transceivers from 70's. The "two-mixer + 1 XTAL filter" design uses the 1st mixer as front-end mixer on receive as well as SSB modulator on transmit. The second mixer is used as SSB product detector on receive and as a heterodyne mixer on transmit. VFO and BFO are cross-switched between both mixers with a PIN diode matrix. Between 1st mixer's output and 2nd mixer's input a crystal filter is placed, followed by an AGC PIN attenuator. AF/RF passive splitter (combiner) takes care about the proper separation of AF and RF signals at the 2nd mixer's output as well as combining them at the 1st mixer's input. The antenna switching between receiver and transceiver is done by a single 1N4007 diode. No relays are used in the transceiver.
Both implemented mixers are AD831 type, XTAL filter is made of six 6,400 MHz crystal units and has approx. 2,7kHz of bandwidth.
There is no SSB/CW mode switch. With the activated PTT button you are "on-air" in phone mode, if you push the KEY, you are "on-air" CW. CW mode has priority over SSB mode. CW can be operated in either LSB or USB.
Homemade 80m 5W SSB/CW transceiver