HI All,
I have an Yaesu FT980 with what appears to be VFO problems. The symptoms are:
- The VFO display tracks well but the actual frequency changes in broken steps like a decade counter is bad. Also, the VCO has a 200 to 400hz warble.
- The IF bandwidth also seems to have problems, maybe unrelated.
- No other noticable problems, great Pout (110watts), etc.
Anyone know any common FT980 failures to check for?
Thanks,
john
FT980 VFO unstable
Almost any time a VFO is unstable, be it analog or digital, the problem can be traced to a bad voltage regulator. In this case, it sound to me like a devider/counter is not getting a proper signal level from a clock and is "missing" some pulses. These pulses are probably there, but too low to cross over from the "0" to "1" state, which is making the VFO "warble".
Does the radio have a second VFO, either internal or external , that you could try? Does the radio do this on all bands, or just a few? Is it doing it in transmit as well as receive or just receive? Most modern rigs are triple or more conversion, and have a "master" oscillator running at a very high frequency, with the other oscillators hetrodyning or mixing with this oscillator. Try to isolate the problem to one stage or the other.
Good luck, and I hope someone with a schematic or more direct knowledge of that radio can help you out. I'm sorry that I can only give you some general advice.
73 from Jim AG3Y
Does the radio have a second VFO, either internal or external , that you could try? Does the radio do this on all bands, or just a few? Is it doing it in transmit as well as receive or just receive? Most modern rigs are triple or more conversion, and have a "master" oscillator running at a very high frequency, with the other oscillators hetrodyning or mixing with this oscillator. Try to isolate the problem to one stage or the other.
Good luck, and I hope someone with a schematic or more direct knowledge of that radio can help you out. I'm sorry that I can only give you some general advice.
73 from Jim AG3Y