[Elecraft] [K3] Test Mode TX and TX Monitor?

[Wes (N7WS)]

If I had to guess, which is exactly what I'm doing, I think either the LPA or 
the HPA is generating a spurious signal and it sees a mismatch into your BPF.  I 
would try to get it into this state and use your other radio to sniff around.


On 9/29/2015 11:59 AM, Dan Atchison wrote:
> To answer a few questions, I'll try to be as definitive as possible.
>
> I see, according to both the P3 TX Mon AND the LP-100A up to about 0.4 watts 
> output from the K3S on CW mode in TEST.  The sensors for both the TX Mon and 
> the LP-100A are in series, the TX Mon immediately after the K3S and the 
> LP-100A through a short piece of RG-400.  If I substitute the K3 for the K3S, 
> there is no indication on either "wattmeter."  So methinks that this proves an 
> issue with the K3S.
>
> Also what is interesting is if I monitor the K3S signal (while in TEST mode) 
> on the K3, the signal level pins the meter on the K3. Reverse (the K3 
> transmitting in TEST MODE to the K3S), it's about S7.  Not a great test, but 
> significant I think. It's almost like a short spike of power is output (as 
> indicated on the P3 TX Mon and LP-100A).  I contacted a local ham but he 
> cannot hear any transmitted signal (he's about 7 air miles away), but methinks 
> it's a spike of such short duration or generation that he wouldn't.
>
> I am also seeing an anomaly with the K3S that I have yet to fully understand 
> and as far as I can tell happens only on 80M.
>
> I run SO2R and have bandpass filters between the K3S and K3 and their 
> respective amplifiers.  On 80M, and according to the internal K3S wattmeter, I 
> have a 1:1 swr going into the bandpass filter but as soon as the rig output is 
> set to above 12 watts, i.e. the KPA3A kicks in, the SWR immediately rises to 
> 5:1.  The SWR remains high until I increase the power up to about an indicated 
> 45 W output (by virtue of the power control on the K3S), then the SWR 
> immediately reduces back to 1:1 and remains there to max power output.  Of 
> course the "real" power output is cut back until the SWR goes down.  So, you 
> say, it's the bandpass filter. Perhaps, but I have swapped bandpass filters 
> and the problem remains with the K3S.  I have also eliminated the amplifiers 
> by installing a dummy load in their place.  I did this to make sure the KPA3A 
> was not transmitting a dirty signal on some other frequency against a resonant 
> 80M antenna.  Same issue.  There are no issues with the K3 in line - it's only 
> the K3S.
>
> I realize, because the K3S has the new KAT3A with a bypass relay as well as 
> the upgraded KPA3A, that things are different than the K3, but still???  Some 
> kind of matching anomaly?
>
> I plan on sending the K3S back to Elecraft to witness this (and yes, I will 
> include the bandpass filter), but rumor has it that their repair center is 
> backlogged and it's too close to contest season to risk being without.  My K3S 
> works fine except for these problems.
>
> 73,
> Dan
>