[K3] Test Mode TX and TX Monitor?

[Dan Atchison]

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


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[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
>

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[wayne burdick]

Dan,

This is very odd behavior. There should be no output in TEST mode, and no contribution to SWR from the KAT3A. The two problems may be related.

I hope you can return the rig to us for analysis. It will of course be covered under warranty.

73,
Wayne
N6KR

On Sep 29, 2015, at 11:59 AM, Dan Atchison <[hidden email]> wrote:

> To answer a few questions, I'll try to be as definitive as possible.


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