by Clive G7LUC » Mon Feb 24, 2020 4:57 pm
Hi folks,
For those who did see my previous (first ever) forum post, I'm a total HF “newbie” even though I've held my old “Class B” licence since 1992. I'm recently retired and just setting up my first HF transmitting station centred around a 1979 vintage Yaesu FT-7 transistor portable.
The FT-7 is a really good unmodified original example with a super-sensitive receiver for which the model is renowned. Nominal output for this model on transmit is 10W CW and SSB. I have had two UK QSO's so far , both SSB on 80m, so the TX is certainly functional. The problem is that power seems to be down.
Using a power meter of known accuracy and using dummy load, CW power is a healthy 12W, no problem. But I can't get more than 5W on SSB, even shouting into the mike at point blank range. I've tested the mike (the original Yaesu fist type) on an audio amp and its as good as any other dynamic mike in my collection in terms of sensitivity and volume.
Adjusting the mike level on the FT-7 seems make little difference. It's calibrated 1-8 and anything above 2 gets the same 5W maximum output on the power meter. The lower scale on the S meter is for the PA transistor collector current on transmit. This shows 3 amps on CW but only about half that on normal speech levers for SSB, never above 2 amps.
SSB is new to me except for what I had to learn about it to pass the RAE in 1992. But it seems to me that the transmitter is not getting enough drive on SSB. Or, if you like, the modulation level is too low. This is assuming that 10W is actually supposed to be achievable on SSB on this set?
I have the Yaesu manual for the FT-7 which is pretty detailed but a can't seem to find anything about “modulation level setting.” I know about the “two tone test” but don't have a 'scope so that's out, I'm afraid.
Does it seem to you experienced folks that my FT-7 is down on SSB transmit power?
Your advice always very welcome.
Clive
Hi folks,
For those who did see my previous (first ever) forum post, I'm a total HF “newbie” even though I've held my old “Class B” licence since 1992. I'm recently retired and just setting up my first HF transmitting station centred around a 1979 vintage Yaesu FT-7 transistor portable.
The FT-7 is a really good unmodified original example with a super-sensitive receiver for which the model is renowned. Nominal output for this model on transmit is 10W CW and SSB. I have had two UK QSO's so far , both SSB on 80m, so the TX is certainly functional. The problem is that power seems to be down.
Using a power meter of known accuracy and using dummy load, CW power is a healthy 12W, no problem. But I can't get more than 5W on SSB, even shouting into the mike at point blank range. I've tested the mike (the original Yaesu fist type) on an audio amp and its as good as any other dynamic mike in my collection in terms of sensitivity and volume.
Adjusting the mike level on the FT-7 seems make little difference. It's calibrated 1-8 and anything above 2 gets the same 5W maximum output on the power meter. The lower scale on the S meter is for the PA transistor collector current on transmit. This shows 3 amps on CW but only about half that on normal speech levers for SSB, never above 2 amps.
SSB is new to me except for what I had to learn about it to pass the RAE in 1992. But it seems to me that the transmitter is not getting enough drive on SSB. Or, if you like, the modulation level is too low. This is assuming that 10W is actually supposed to be achievable on SSB on this set?
I have the Yaesu manual for the FT-7 which is pretty detailed but a can't seem to find anything about “modulation level setting.” I know about the “two tone test” but don't have a 'scope so that's out, I'm afraid.
Does it seem to you experienced folks that my FT-7 is down on SSB transmit power?
Your advice always very welcome.
Clive