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Upgrading an old Yaesu FRG-7
Good Day all!
I have recently got one of these sets and am rapidly upgrading the original design. So far it has a Kokusai Mech filter, manual and AGC Rf gain control on the RF stage. It has also had improvements to its AGC system and I am about to update the RF stage FET. One problem has arisen and someone might be able to help me here. The Kokusai filter is NOT actually on 455 kHz, it's actual centre frequency is 454.2 kHz (measured against a calibrated frequency counter), Since the self excited BFO is NOT drift free I want to replace it with USB/LSB Xtals. Can you still get the old time FT241 types, or does anyone know a source of odd frequencies in the 455/465 kHz IF range? I calculate that the the old FT241 channels I would need would be 328 and 326. That would give me BFO frequencies of 455.55 (should be 455.7) and 452.7 kHz that fits in with the odd filter. That way one of the main sources of drift should be almost gone. I have found that the FRG-7 has its problems, but, as someone who has designed and built many communication receivers over the years IMO it is the basis for quite a useful general coverage receiver and a VERY useful bit of test gear with noise bridges etc. Any suggestions gratefully received. 73's Cliff Wright ZL1BDA ex G3NIA New Zealand. |
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