Jim,
There is no relay action when changing from VFO A to B or the other way
around - the MCU just sends different data to the PLL and PLL Reference
Oscillator.
However, 20 MHz may be on the lower limit of the available VFO tuning
range for 15 meters.
Try tuning the VFO for both A and B back into the 15 meter band limits.
73,
Don W3FPR
On 7/3/2019 3:57 PM, Jim KO5V wrote:
Hi again,
I did as Don suggested, and checked the values of all of the capacitors around
U1, and all of the band-switching relays. I also re-flowed all of their solder
joints. With the bottom panels, top panel and the left-side panel off, the
click in the audio was a lot better, and switching VFOs on 15M was quiet.
However, after I put it all back together, it's all returned. I looked the the
S-meter, and with the RF gain set fully cw, I see the following brief readings
that accompany the clicks and pops in the speaker:
15M, VFO A to VFO B: S1;
*15M, VFO B to VFO A: S9;
15M-17M: S1;
17M-15M: click, no reading;
*15M-12M: S5;
12M-15M: click, no reading;
20M-30M: click, no reading;
30M-20M: click, no reading.
The other bands/VFOs switch quietly.
Otherwise, the radio seems to work just fine, and has been performing well. I
recently set 15M VFO B to 20MHz WWV, and that's when I noticed this. I wonder
if I should just forget about it, except the S5 and S9 pops just don't give me
a good feeling.
How does the radio switch between VFO A and VFO B? I assume it's done in the
firmware, but is some relay (or a band-specific relay) involved?
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