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K3: Power output low on 30 meter band

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Phil Hystad

K3: Power output low on 30 meter band

Since putting together my K3 two weeks ago I had a chance to try it out on 30 meters today. I tuned up my delta loop to 10 meters and then noticed that the power was low. I thought that maybe my meters were reading funny or something funny about the antenna so I switched over to my Icom 756 Pro III to try the same antenna. It was dead on with a 1.1:1 SWR on the same frequency of 10.106 MHz. And, the meters for the Pro III were reading about 101 watts output (two different meters).

So I switched the antenna back to the K3 and checked the SWR and it was about the same, 1.2:1 for the same frequency. But, the power output is only about 65 watts even though the power adjust knob reads 100 watts. I tried different readings and about 55 watts, the external meter power output starts to flatten out compared to the digital readout of the power on the K3 (the external meter is an LP-100A).

All other bands show good power output.

Any hints?

73, phil, K7PEH
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Phil Hystad

Re: [Elecraft] K3: Power output low on 30 meter band

OK, I fixed the problem. The SWR reading on the K3 meter was showing about a 2.8:1 SWR. Obviously I forgot to tune through the ATU. I did that and it fixed the problem.

peh

Begin forwarded message:

> From: Phil Hystad <[hidden email]>
> Date: January 23, 2010 3:43:45 PM PST
> To: Elecraft Discussion List <[hidden email]>
> Subject: [Elecraft] K3: Power output low on 30 meter band
>
> Since putting together my K3 two weeks ago I had a chance to try it out on 30 meters today. I tuned up my delta loop to 10 meters and then noticed that the power was low. I thought that maybe my meters were reading funny or something funny about the antenna so I switched over to my Icom 756 Pro III to try the same antenna. It was dead on with a 1.1:1 SWR on the same frequency of 10.106 MHz. And, the meters for the Pro III were reading about 101 watts output (two different meters).
>
> So I switched the antenna back to the K3 and checked the SWR and it was about the same, 1.2:1 for the same frequency. But, the power output is only about 65 watts even though the power adjust knob reads 100 watts. I tried different readings and about 55 watts, the external meter power output starts to flatten out compared to the digital readout of the power on the K3 (the external meter is an LP-100A).
>
> All other bands show good power output.
>
> Any hints?
>
> 73, phil, K7PEH
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html

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Dunc Carter - W5DC

Re: [Elecraft] K3: Power output low on 30 meter band

In reply to this post by Phil Hystad

A few days ago, I repaired my K3 which had this problem as it came from
the factory. After following diagnostic instructions from Elecraft,
what I found was that the band pass filter at the level that includes
the drive to the transverter output was mis-tuned.
The following is part of my report my report to Wayne and to Elecraft
support. C179 and C183 are trimmer capacitors for the band pass filter
at the level before the transceiver output. If you don't have the
optional transceiver output accessory, this method becomes more difficult.

"C179 was peaked, I assume properly.

C183 was stuck and didn't want to turn with the alignment tool. I used
a jeweler's screwdriver that didn't have an insulated sheath and
"un-stuck" C183. Next, I peaked C183. At 10.149, a cw tone is 2.3
divisions peak on the scope; at 10.101, the cw tone is 2.1 divisions.
Reverting to normal HF mode, 110 watts output is reached with no
problem. The other bands seem unchanged with normal full output, etc. "

The diagnostic process that I followed requires that you have something
to measure the drive level at that point on 30 meters and also 40
meters; a used a dual trace 30 MHz oscilloscope.

Another possibility is that a 8.215 MHz notch filter is mis-tuned;
apparently this has happened before.

Let me know if you need more info.. Wayne and Elecraft support in the
person of Gary Surrency were quite helpful.

Dunc, W5DC

Phil Hystad wrote:

> Since putting together my K3 two weeks ago I had a chance to try it out on 30 meters today. I tuned up my delta loop to 10 meters and then noticed that the power was low. I thought that maybe my meters were reading funny or something funny about the antenna so I switched over to my Icom 756 Pro III to try the same antenna. It was dead on with a 1.1:1 SWR on the same frequency of 10.106 MHz. And, the meters for the Pro III were reading about 101 watts output (two different meters).
>
> So I switched the antenna back to the K3 and checked the SWR and it was about the same, 1.2:1 for the same frequency. But, the power output is only about 65 watts even though the power adjust knob reads 100 watts. I tried different readings and about 55 watts, the external meter power output starts to flatten out compared to the digital readout of the power on the K3 (the external meter is an LP-100A).
>
> All other bands show good power output.
>
> Any hints?
>
> 73, phil, K7PEH
> ______________________________________________________________
> 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
>
>