Re: R4C Passband Tuning ?
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Bob & Group, I think I've got it solved. Using an IFR1200S (GPS ref) service monitor, I tuned the R4C and T4XC oscillators to 5645, as well as the AM oscillator. My R4C (recently back from service) oscillator was 1.4 KHz low, which was the issue. I re-adjusted T-11 for bandpass center. Thanks all 73 Jay W6CJ
I am going from memory and do not have a manual in front of me. So here goes.
The incoming signal to the R-4C is converted to the first IF of 5.645-MHz. In the second mixer, SSB and CW signals are converted to 5.695-MHz with the 50-kHz BFO signal.?
The signal passes through the selected the second IF filter to the third mixer. The oscillator for the third mixer is from an oscillator located under the filter shield located rear center, top side of the receiver.?
There is one oscillator with two crystals, one being 5.645-MHz that is used on SSB and CW to produce the 50-kHz third IF. The frequency of the other oscillator I forget but it converts AM signals at 5.645-MHz to 50-kHz.
To get the receiver 5.645-MHz oscillator on the same frequency as the signal on the "Carrier Osc" lead from the T-4XC, there is a variable capacitor for adjustment. It is under that shield on the same PC board with the oscillator and adjustment capacitors of the R-4C. Yes, the other variable capacitor is for the AM oscillator.?
Maybe someone can pipe in here with the capacitor designators.
73 and Merry Christmas to all.
Bob Loving K9JU
Maryville, TN
On Tuesday, December 24, 2024 at 04:25:16 PM EST, Rob Sherwood via <rob= [email protected]> wrote:
Yes. Rob
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Rob,
Connect my service monitor/counter to the CAR OSC jack, and adjust C6 for exactly 5645 Khz?
Tnx&73
Jay
W6CJ
The 5645 kHz LO from the transmitter if off frequency.? Rob, NC0B?
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Group,
I have my "new" Twins hooked up and making QSOs.
I noticed that with the R4C in LSB, and passband on the LSB "dot" for best LSB reception........? when I turn on the T4XC, I have to re-tune the R4C passband down to the RTTY region, for LSB reception to sound the same.
Is this normal?
What would cause the passband tuning shift?
Merry Christmas & 73
??????
Jay
W6CJ
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Jay W6CJ