This radio started as a very neglected FRG7, too rough to repair, too good to throw out. With the help of an angle grinder, the top chassis section was removed, and new alloy chassis plates fitted. The new circuitry I designed around vacuum tubes, arranged to use the existing Yaesu front panel controls.
The radio? works as intended, an MDS of -108 dB, and a -91dB sensitivity for a 12dB SINAD, slightly better than the solidstate version.
The frequencies used are similar to the Racal RA17, with the first IF at 40 mHz, the loop at 37.5, as apposed to the? FRG freqs at 52 and 55 megs.
Tubes are 6AU6s for all loop amplifiers and mixer stages, 6BA6 remote cut off pentodes for AGC controlled stages, ECH81 triode/heptodes , 1 each for the 4th mixer and VFO, product detector and BFO, 6BL8 for the 2nd mixer and audio preamp, and an OB2 neon for voltage stabilisation.... 15 in all. I even managed to replicate the Yaesu lock LED, this time it glows green when locked.........
