Elecraft

Re: Calibrating the P3 Station Monitor?

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Don Wilhelm

Re: Calibrating the P3 Station Monitor?

Peter,

Realistic instrument errors are up to 20% - check the ARRL Product reviews.
It just seems your Alpha meter is off in one direction and the TX
MONitor is off in the other direction.

See if you can borrow an LP100 wattmeter which has been calibrated by
N3LP to NIST tracable standards. That will provide you with an up to 5%
error. Larry is reluctant to specify the error any closer than 5%.

In this age of digital displays, we have a tendency to believe that the
display is accurate down to the last displayed digit. More often than
not, that is not true.

73,
Don W3FPR

On 7/19/2018 5:33 PM, Peter Dougherty wrote:

> Hi all,
> I recently installed a TX MON to my P3, and the readings are seemingly far off
> compared to two other meters. The 1.8-54 Mhz/2kW sensor was placed where my
> existing Alpha 4510 meter was connected (after the amp and low-pass filter,
> before the tuner), so I was expecting readings that were more-or-less close.
> However the TX MON is reading far below both the Alpha meter it's replacing and
> the power indicated on my Palstar HF-Auto tuner.
>
> Here are some sample readings, all of which are using the default 500ms
> TXMonMenu/SensorCal setting, running into a Cantenna resistive dummy load,
> keying down with 27 WPM dits
>

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Peter W2IRT

Re: Calibrating the P3 Station Monitor?

I'm good with about a 10% error (on the cautious side), and since I'm a contester, I want to ensure I'm never over about 1425 Watts when I'm competing. The Alpha 4510 was supposedly calibrated to known standards as well (for $1150 new it darned well better have been). I can live with it reading a tad high. However I was hoping to sell it to help fund my upcoming KP-1500 purchase, but the TX MON doesn't seem to be the solution, which is most unfortunate. I love what it does, but the accuracy is a problem.

- pjd

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Thursday, July 19, 2018 6:35 PM
To: Peter Dougherty; [hidden email]
Subject: Re: [Elecraft] Calibrating the P3 Station Monitor?

Peter,

Realistic instrument errors are up to 20% - check the ARRL Product reviews.
It just seems your Alpha meter is off in one direction and the TX
MONitor is off in the other direction.

See if you can borrow an LP100 wattmeter which has been calibrated by
N3LP to NIST tracable standards. That will provide you with an up to 5%
error. Larry is reluctant to specify the error any closer than 5%.

In this age of digital displays, we have a tendency to believe that the
display is accurate down to the last displayed digit. More often than
not, that is not true.

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Lovin' my K3S (S/N 10023)
73, Peter W2IRT

k6dgw

Re: Calibrating the P3 Station Monitor?

Most any Tektronics or HP scope, even if old, will hold its calibration,
particularly the vertical, for a long time if it has been treated well.
I have a very old Tek 422 which I had a chance to have calibrated for
free a couple of years ago and it was essentially within 2% or less on
all ranges after many years. If you have a scope, or have access to
one, you can measure the P_P voltage across a good DL and do a little
arithmetic. I'd measure the DL first, my old Cantenna measured almost
90 ohms after 25 years. [:-) An old Bird came in at 54 ohms.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 7/19/2018 3:40 PM, Peter W2IRT wrote:

> I'm good with about a 10% error (on the cautious side), and since I'm a contester, I want to ensure I'm never over about 1425 Watts when I'm competing. The Alpha 4510 was supposedly calibrated to known standards as well (for $1150 new it darned well better have been). I can live with it reading a tad high. However I was hoping to sell it to help fund my upcoming KP-1500 purchase, but the TX MON doesn't seem to be the solution, which is most unfortunate. I love what it does, but the accuracy is a problem.
>
> - pjd
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: Thursday, July 19, 2018 6:35 PM
> To: Peter Dougherty; [hidden email]
> Subject: Re: [Elecraft] Calibrating the P3 Station Monitor?
>
> Peter,
>
> Realistic instrument errors are up to 20% - check the ARRL Product reviews.
> It just seems your Alpha meter is off in one direction and the TX
> MONitor is off in the other direction.
>
> See if you can borrow an LP100 wattmeter which has been calibrated by
> N3LP to NIST tracable standards. That will provide you with an up to 5%
> error. Larry is reluctant to specify the error any closer than 5%.
>
> In this age of digital displays, we have a tendency to believe that the
> display is accurate down to the last displayed digit. More often than
> not, that is not true.
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Jim Brown-10

Re: Calibrating the P3 Station Monitor?

In reply to this post by Peter W2IRT

On 7/19/2018 3:40 PM, Peter W2IRT wrote:
> I'm good with about a 10% error (on the cautious side), and since I'm a contester, I want to ensure I'm never over about 1425 Watts when I'm competing.

Several years ago, I bought W6OSP's LP100A from his estate. It came with
one sensor, and I bought a second, sending the first back to Larry to
calibrate for me. I have one sensor on the output of both power amps,
and the LP100A autoswitches to display the one that is transmitting.

I'm VERY happy with it. I'm currently using a borrowed KPA1500, and find
that the amp and the LP100A are within a 1-2 percent of each other.

73, Jim K9YC

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