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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