Tim,
Since the RX sensitivity is good below 1800 kHz, on the surface, that
would indicate that either the 160 meter Low Pass Filter or the bandpass
filter has a problem and the cutoff frequency is too low.
Count the turns on the two toroids on the K160RX option board - each
should have 21 turns and the cores should be blue.
Secondly, check the capacitor values on the K160RX board - C1 and C3
should be 1500 pF and C2 should be 2700 pF.
For the bandpass filter, check the value of capacitors C13 and C14 -
they should be 1200 pF.
If it has never worked on 160, my first guess is that you will find the
1200 pF capacitors on the K160RX board and the 1500 pF capacitors in the
bandpass filter, but that remains to be seen.
Also check the voltage at the left end of R30 (about 1 inch from the
left side of the RF board toward the front). Check when tuned to 1800
kHz and also at 2000 kHz. Ideally that voltage should be higher than
1.5 volts (although 1 volt will likely be OK) but not greater than 7 volts.
73,
Don W3FPR
On 6/29/2013 2:28 PM, NZ8J wrote:
I just bought a K2/10 that I knew had a problem on 160 before I got it
and now am looking for some help or if anyone has run across similar
symptoms before.
1. The radio works perfectly on 80-10 meters full power output and good
sensitivity (serial number 41XX)
2. Using the BAND +/- buttons to go to 160 meters will sometimes result
in good sensitivity on 160 indicated by band noise, etc, depending on
how long it has been since the band switch was on 160.
3. with the power to 5 watts or higher, doesn't matter) the power
output will be about 1 to 2 watts when holding the TUNE button. However
the power gradually drops to almost zero in a short time, just a matter
of seconds.
4. when the sensitivity is good on 160 (as indicated in 1 above), just
leaving the radio alone and not touching anything, the sensitivity
slowly drops off until nothing is heard from the speaker, just like
someone turned the RF gain back
5. basically it seems like 160 function works on either TX or RX until
something heats up or some time related action takes place and 160 just
dies.
6. another part of the puzzle. When the sensitivity drops off on 160, if
I turn the frequency somewhere below 1.800 khz the sensitivity returns,
and then when I go back up above 1.800 khz it immediately drops off
again..
I've removed the cover and unplugged the 160 module, looked it over and
reheated all the connections on it. Nothing seems amiss there. I tried
tuning L3 and L4 and it doesn't seem to have any affect on the power
output ( in the short time I have to check before it drops off
completely)
Any ideas.. Whatever the problem is, it appears to be related to both TX
and RX and only affects 160, no other bands or functions are affected.
Thanks for any help or ideas..
Tim
NZ8J
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