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Update of Fred Cady's K3 book?

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Jim Low man

Update of Fred Cady's K3 book?

I understand that Fred Cady may be publishing an addendum to his
excellent K3 book, to include the K3S.

Any information?

73 de Jim - AD6CW
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Robert Nobis - N7RJN

P3TXMON VSWR Measurement Accuracy

I am having a VSWR measurement accuracy issue with my P3TXMON. I have a calibrated VSWR tester that indicates my antenna and feedline VSWR is 1.05:1. When I connect the P3TXMON and transmit, the PS display shows my VSWR is 2.0:1 into my feedline and antenna.

I also tried testing into a dummy load. The VSWR tester shows a VSWR into the dummy load of 1.01:1, whereas the P3TXMON shows a VSWR of 1.29:1.

Power level readings on the P3TXMON are within 5% of measured power levels using a power meter, so the P3TXMON is reasonably accurate measuring the transmitted power.

In reviewing the P3 manual, I do not see any methodology for calibrating the VSWR measurement accuracy for the P3TXMON.

Any suggestions on how to calibrate the P3TXMON for better measurement accuracy?

Thanks and 73,

Bob Nobis - N7RJN
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Wes (N7WS)

Re: P3TXMON VSWR Measurement Accuracy

I can't speak to the P3TXMON accuracy. I don't think it's specified anywhere,
however, I don't own one and just skimmed the documentation.

That said, you should be worrying about your "calibrated" VSWR tester. It's
lying to you. You would pay big bucks to get a precision termination guaranteed
to 1.01 (46 dB return loss).

To have a power dummy load that good would be astounding.

On 9/8/2015 10:49 AM, Robert Nobis wrote:

> I am having a VSWR measurement accuracy issue with my P3TXMON. I have a calibrated VSWR tester that indicates my antenna and feedline VSWR is 1.05:1. When I connect the P3TXMON and transmit, the PS display shows my VSWR is 2.0:1 into my feedline and antenna.
>
> I also tried testing into a dummy load. The VSWR tester shows a VSWR into the dummy load of 1.01:1, whereas the P3TXMON shows a VSWR of 1.29:1.
>
> Power level readings on the P3TXMON are within 5% of measured power levels using a power meter, so the P3TXMON is reasonably accurate measuring the transmitted power.
>
> In reviewing the P3 manual, I do not see any methodology for calibrating the VSWR measurement accuracy for the P3TXMON.
>
> Any suggestions on how to calibrate the P3TXMON for better measurement accuracy?
>
> Thanks and 73,
>
> Bob Nobis - N7RJN
> [hidden email]
>
>

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Don Wilhelm-4

Re: P3TXMON VSWR Measurement Accuracy

In reply to this post by Robert Nobis - N7RJN

Bob,

How are you testing?
If you are testing with the P3TXMON and your 'calibrated VSWR tester' in
series with your feedline, then those numbers may be incorrect.
The 'calibrated VSWR tester' is reading the SWR seen looking into your
antenna, but the P3TXMON is looking at the SWR looking into the input of
your VSWR tester - and that may be two different things.

If you want to do a valid test, obtain the SWR reading on your VSWR
tester, and then take the feedline off that tester and connect it to the
P3TXMON directional coupler and compare the SWR reading obtained from
that combination.

In other words, while your VSWR tester may be calibrated at its output,
there is no guarantee that its coupler does not introduce an SWR at its
input. Switching the same coax from the output of your tester to the
output of the P3TXMON is the only valid test.

73,
Don W3FPR

On 9/8/2015 1:49 PM, Robert Nobis wrote:

Robert Nobis - N7RJN

Re: P3TXMON VSWR Measurement Accuracy

Don,

Thank you. I tested separately. When using the P3TXMON, the calibrated tester was not in the transmission path. I actually did what you suggested in your second paragraph.

As another test, I borrowed another ham’s Elecraft W2 SWR meter. I replaced the PSTXMON with the W2. The readings using the W2 software utility were close to the readings from my tester, about 1.08:1. Significantly, different than the reading form the P3TXMON of 2.0:1.

73,

Bob

Bob Nobis - N7RJN
[hidden email]

> On Sep 8, 2015, at 15:23, Don Wilhelm <[hidden email]> wrote:
>
> Bob,
>
> How are you testing?
> If you are testing with the P3TXMON and your 'calibrated VSWR tester' in series with your feedline, then those numbers may be incorrect.
> The 'calibrated VSWR tester' is reading the SWR seen looking into your antenna, but the P3TXMON is looking at the SWR looking into the input of your VSWR tester - and that may be two different things.
>
> If you want to do a valid test, obtain the SWR reading on your VSWR tester, and then take the feedline off that tester and connect it to the P3TXMON directional coupler and compare the SWR reading obtained from that combination.
>
> In other words, while your VSWR tester may be calibrated at its output, there is no guarantee that its coupler does not introduce an SWR at its input. Switching the same coax from the output of your tester to the output of the P3TXMON is the only valid test.
>
> 73,
> Don W3FPR
>
> On 9/8/2015 1:49 PM, Robert Nobis wrote:
>> I am having a VSWR measurement accuracy issue with my P3TXMON. I have a calibrated VSWR tester that indicates my antenna and feedline VSWR is 1.05:1. When I connect the P3TXMON and transmit, the PS display shows my VSWR is 2.0:1 into my feedline and antenna.
>>
>> I also tried testing into a dummy load. The VSWR tester shows a VSWR into the dummy load of 1.01:1, whereas the P3TXMON shows a VSWR of 1.29:1.
>>
>> Power level readings on the P3TXMON are within 5% of measured power levels using a power meter, so the P3TXMON is reasonably accurate measuring the transmitted power.
>>
>> In reviewing the P3 manual, I do not see any methodology for calibrating the VSWR measurement accuracy for the P3TXMON.
>>
>> Any suggestions on how to calibrate the P3TXMON for better measurement accuracy?
>>
>>
>
>

Robert Nobis - N7RJN

Re: P3TXMON VSWR Measurement Accuracy

In reply to this post by Wes (N7WS)

Wes,

The 1.01 is what the reading indicated. It could easily be higher. Even if it were 1.1:1 it is significantly different that the 2.0:1 reading of eh P3TXMON.

Thanks and 73,

Bob Nobis - N7RJN
[hidden email]

> On Sep 8, 2015, at 15:05, Wes (N7WS) <[hidden email]> wrote:
>
> I can't speak to the P3TXMON accuracy. I don't think it's specified anywhere, however, I don't own one and just skimmed the documentation.
>
> That said, you should be worrying about your "calibrated" VSWR tester. It's lying to you. You would pay big bucks to get a precision termination guaranteed to 1.01 (46 dB return loss).
>
> To have a power dummy load that good would be astounding.
>
> On 9/8/2015 10:49 AM, Robert Nobis wrote:
>> I am having a VSWR measurement accuracy issue with my P3TXMON. I have a calibrated VSWR tester that indicates my antenna and feedline VSWR is 1.05:1. When I connect the P3TXMON and transmit, the PS display shows my VSWR is 2.0:1 into my feedline and antenna.
>>
>> I also tried testing into a dummy load. The VSWR tester shows a VSWR into the dummy load of 1.01:1, whereas the P3TXMON shows a VSWR of 1.29:1.
>>
>> Power level readings on the P3TXMON are within 5% of measured power levels using a power meter, so the P3TXMON is reasonably accurate measuring the transmitted power.
>>
>> In reviewing the P3 manual, I do not see any methodology for calibrating the VSWR measurement accuracy for the P3TXMON.
>>
>> Any suggestions on how to calibrate the P3TXMON for better measurement accuracy?
>>
>> Thanks and 73,
>>
>> Bob Nobis - N7RJN
>> [hidden email]
>>
>>
>
> ______________________________________________________________
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