[Elecraft] K2 160 meter issue??

[Don Wilhelm]

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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