Converting the FRG-7 to true SSB (all the mods)
Designed by sv3ora

The schematic above shows all the modifications needed to convert the FRG-7 into true SSB. It involves installing an auxiliary ssb filter (CFJ455K-5) decreasing the range of the fine tuning capacitor and stabilizing the unstable BFO with a PLL.

The Yaesu FRG-7 is
a general coverage MW/SW receiver that uses the Wadley Loop system for stabilizing the frequency tuning. The receiver has a good sound on AM mode, that reminds me the tube receivers sound. However, on sideband mode, it is pretty much useless. The IF ceramic filter that is used, does not have enough selectivity to reject the opposite sideband. No matter if the front panel mode selector switch states USB/CW and LSB, these just shift the BFO, nothing more. The receiver is a DSB set not SSB. Further more the BFO is very unstable for SSB operation and it drifts badly when the radio is heated, affecting the pitch of the sideband.

By performing these modifications, you will end up with an FRG-7 receiver that is trully selective, allowing for real SSB reception. Most importantly you do not ruin the appearance of your prescious FRG-7, but just improving it's performance. This modifications would probably be appreciated much when deciding to sell your FRG-7 to someone else.

The filter I used is the Murata CFJ455K5 SSB ceramic filter. This made things compact. Because of this, I made a tiny PCB with the two ceramic filters onto it and I placed this PCB vertical, right at the pads where the original AM filter was soldered onto the FRG-7.

Next there are some more photos of the rest of the modifications. Note that I built the PLL inside the middle metal that holds the batteries, so that it is well shielded.

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