Hi.
I tried out 20m for the first time this weekend after having completed
the KXB3080 module.
It works FB, I'm having great fun on 80m... and the 20m worked great,
exchanged 2 X 599 reports with a station running 5W in Georgia...
but...
I realized that one thing which I thought was my imagination the first
couple of times I saw it is really a problem, and I also made the
observation that after the mod I have a lot of internally generated
spurious signals (birdies) on 20m which were not there beforehand.
(1) Rotary Encoder Quirk
If I set the tuning rate to XX.X kHz and then slowly rotate the tuning
knob of the KX1, I notice that for the most part, the tuning does
exactly what you would expect "05.7, 05.8, 05.9, 06.0, 06.1, ...".
Now and again though, it jumps back a couple of 10ths of a kHz. I
captured this behavior in this movie:
http://www.sunim.plus.com/encoder_quirk.avi
Throughout the movie, I slowly rotate the tuning control positively in
the clockwise direction. The digits increment correctly right up
until "12.0". Then we see this happen:
"12.0, 12.1, 12.2, 12.3, 12.1, 12.2, 12.3, 12.1, 12.2, 12.3, 12.5..."
So - twice the frequency jumped backwards by 0.2kHz even although the
tuning control is being moved clockwise.
This seems to happen at random, on all bands. I noted where the
screw-hole in the side of the tuning knob was pointed to see if it
always happened at the same point in the tuning knob cycle but it
doesn't - it seems to be truly random.
(2) 20m birdies
I've always had a birdie at 14066.1kHz. It sounded stronger after the
KXB3080 mod, which I put down to the 20m sensitivity having been
increased by the mod (It's true that audio seems to be stronger on 20m
since the mod).
Now, however, there are numerous (easily 50or more) signals
distributed throughout the 20m band. They are all quite weak but are
certainly there. It seems to be related to the frequency of the DDS -
on the X.XX tuning scale, incrementing by 0.01kHz changes the tone of
the birdie often by quite a lot.
Although I can live with these (they are quite weak) when I'm
listening to QRPp or DX stations which are also weak it can be a
little bit distracting.
I've captured a sample movie where I tune through a small sample of
the 20m band while connected to a 50 ohm resistor:
http://www.sunim.plus.com/20m_birdies.avi
In this movie I scan from 14067kHz to 14060kHz, and I pick out the
strong birdie at 14066.1kHz (which was there before the mod) then the
weaker birdies (which were not present before the mod) at:
14065.6, 14063.6, 14061.5, 14061.3, 14061.15, 14060.24, 14060.19, 14.059.92
---
Any suggestions on where to start with these problems?
Thanks,
Martin.
VA3SIE.
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