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P3TXMON PEP vs K3S/KPA500 PWR?

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MaverickNH

P3TXMON PEP vs K3S/KPA500 PWR?

With K3S/KPA500 PWR knob set to 100W (out on KPA500) I'll see SWR 1.00 on the
P3TXMON (rATU at the antenna base tuned) but the PEP displayed might vary
markedly from WSJT-X FT8 15sec cycle to cycle of TX from 49W, 13W, 66W, 28W,
... What's going on?

Bret/N4SRN

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Nr4c

Re: P3TXMON PEP vs K3S/KPA500 PWR?

Have you set the Lin In Gain according to the K3 manual. If not, the K3 will vary the output power.

Don Wilhelm has very good information on this topic.

Stand by, he’ll likely pop in with all you need to know. He explains it well.

Sent from my iPhone
...nr4c. bill

> On Jun 17, 2018, at 9:26 AM, MaverickNH <[hidden email]> wrote:
>
> With K3S/KPA500 PWR knob set to 100W (out on KPA500) I'll see SWR 1.00 on the
> P3TXMON (rATU at the antenna base tuned) but the PEP displayed might vary
> markedly from WSJT-X FT8 15sec cycle to cycle of TX from 49W, 13W, 66W, 28W,
> ... What's going on?
>
> Bret/N4SRN
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
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MaverickNH

Re: P3TXMON PEP vs K3S/KPA500 PWR?

Yep - got that set with PC at ~30%, WSJT-X slider at ~60% and MIC (Line Gain)
at 18 so 4 bars solid and 5th just flickers. The LEDs on the KPA500 remain
steady, it's just the P3TXMON that seems to vary.

Bret/N4SRN

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Don Wilhelm

Re: P3TXMON PEP vs K3S/KPA500 PWR?

Bret,

Are you using DATA A? If you are using SSB, then you may have some TX
EQ cranked in and the power varying with the audio tone.
DATA A automatically sets compression to zero and equalization flat. Be
certain to open up the bandwidth to maximum. DATA A defaults to a
narrow bandwidth.

73,
Don W3FPR

On 6/17/2018 1:02 PM, MaverickNH wrote:
> Yep - got that set with PC at ~30%, WSJT-X slider at ~60% and MIC (Line Gain)
> at 18 so 4 bars solid and 5th just flickers. The LEDs on the KPA500 remain
> steady, it's just the P3TXMON that seems to vary.
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Bob McGraw - K4TAX

Re: P3TXMON PEP vs K3S/KPA500 PWR?

In reply to this post by MaverickNH

Based on your settings and description all seem correct. The K3S power
meter should be solid as well. Thus I see the issue is with the P4TXMON.

73

Bob, K4TAX

On 6/17/2018 12:02 PM, MaverickNH wrote:

> Yep - got that set with PC at ~30%, WSJT-X slider at ~60% and MIC (Line Gain)
> at 18 so 4 bars solid and 5th just flickers. The LEDs on the KPA500 remain
> steady, it's just the P3TXMON that seems to vary.
>
> Bret/N4SRN
>
>
>
> --
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MaverickNH

Re: P3TXMON PEP vs K3S/KPA500 PWR?

In reply to this post by Don Wilhelm

Hi Don, I checked and my K3S is set in DATA A mode. I'm running SPLIT as
well. The WSJT-X cites "advantages" but I'm not too clear on what those are!

Bret/N4SRN

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Bob McGraw - K4TAX

Re: P3TXMON PEP vs K3S/KPA500 PWR?

Bret:

Check to see that Data A mode is not showing REV. If so, just press and
hold the ALT button unit the REV is no longer displayed above the DATA
label on the display.

As to SPLIT, that is to assure your transmitted tones are between ~1500
Hz and ~1999 Hz thus any distortion products are outside of the transmit
SSB filter and thus attenuated by the filter.   Thus if you are working
a stations which is at 450 Hz on the waterfall, the software will shift
the VFO such that the correct tone is transmitted to the receiving
station.   All of this is done by the software and the radio under CAT
control.

With the WSJT-X setup, F2 menu, under the GENERAL tab and in the
Behavior box, the VHF/UHF box is not checked.

I did tests with my K3S set at 50 watts. Then transmitted data at 300
Hz, 1200 Hz, 1800 Hz and 2100 Hz. The power output varied between 50
and 55 watts as read on an external power meter, and the K3S power
bargraph always indicated 50 watts.

If your settings and tones from WSJT-X are keeping the ALC bargarph
between 4 and 5 bars then the power output from the K3S should be the
value as set by the PWR control on the radio. Remember, unlike other
radios, the K3S ALC bargraph shows audio level for the first 4 bars.
The actual ALC does not begin until after the 5th bar.   Once set, do
not change the PWR slider on the right side of the WSJT-X panel.   The
actual transmit power is to be controlled only by the PWR control on the
radio.

In my analysis, if your K3S output meter shows constant power and your
KPA500 LED power indication is constant, then the issue lies with the
P3TX MON.

73

Bob, K4TAX

On 6/17/2018 7:08 PM, MaverickNH wrote:

> Hi Don, I checked and my K3S is set in DATA A mode. I'm running SPLIT as
> well. The WSJT-X cites "advantages" but I'm not too clear on what those are!
>
> Bret/N4SRN
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
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