K2, Noise Gen and Spectrogram

[James Kern]

I need to set my K2 Filters. After I had changed one of my chips a few years
ago, I know by operating my K2 that the filters are 'off' and need to be
reset. I had forgotten about it until this Field Day when my K2 was promptly
removed from the table when the filter problem was 'found'.  My friend
previously set them originally using a noise generator and spectrogram. How
is this done? Is spectrogram and a noise generator all I need? I just
ordered the Elecraft NG1.. will this suffice along with Spectrogram? Does
someone have a nice written web page or technical archive on using
spectrogram with any kind of noise generator? Thanks!
 
James, KB2FCV
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[Don Wilhelm-3]

James,

A noise source (NG1 will do nicely) and Spectrogram are all that is required
(ignoring the cable to connect the K2 to the sound card input).

Take a look at the K2 Dial Calibration article on my webpage
http:/w3fpr.qrpradio.com for the information you seek.  If you want to
bypass all the information contained there about setting the reference
oscillator, just skip to "Step 3, Cal FIL".  There are links to additional
information should you need it.

There is also information on the Elecraft website - look in the Builder's
Resources pages.

73,
Don W3FPR

> -----Original Message-----
>
> I need to set my K2 Filters. After I had changed one of my chips
> a few years
> ago, I know by operating my K2 that the filters are 'off' and need to be
> reset. I had forgotten about it until this Field Day when my K2
> was promptly
> removed from the table when the filter problem was 'found'.  My friend
> previously set them originally using a noise generator and
> spectrogram. How
> is this done? Is spectrogram and a noise generator all I need? I just
> ordered the Elecraft NG1.. will this suffice along with Spectrogram? Does
> someone have a nice written web page or technical archive on using
> spectrogram with any kind of noise generator? Thanks!
>
>

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[Evert Bakker (PA2KW)]

Hello James,

The noise generator and spectrogram will do the job!
Look at the www.n0ss.net webpage and you will find the article and
downloadable software including instructions!
With me, it worked.

Good luck,

Evert, PA2KW, K2 #4836


James Kern wrote:

>I need to set my K2 Filters. After I had changed one of my chips a few years
>ago, I know by operating my K2 that the filters are 'off' and need to be
>reset. I had forgotten about it until this Field Day when my K2 was promptly
>removed from the table when the filter problem was 'found'.  My friend
>previously set them originally using a noise generator and spectrogram. How
>is this done? Is spectrogram and a noise generator all I need? I just
>ordered the Elecraft NG1.. will this suffice along with Spectrogram? Does
>someone have a nice written web page or technical archive on using
>spectrogram with any kind of noise generator? Thanks!
>
>James, KB2FCV
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>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
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>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com
>
>  
>

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[Matt Osborn]

Your URL seems not to work. I located your page at

http://www.qsl.net/w3fpr/index.htm.

Should the other work as well?

On Mon, 27 Jun 2005 16:00:30 -0400, "W3FPR - Don Wilhelm"
<[hidden email]> wrote:


>Take a look at the K2 Dial Calibration article on my webpage
>http:/w3fpr.qrpradio.com for the information you seek.
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[G3VVT]

James,
 
Sometimes in addition to a noise generator and a PC with a soundcard  running
Spectrogram you may need to add a 600 ohm 1:1 isolation transformer  between
the LS output of the K2 and the PC sound card input. Perhaps I was  
unfortunate in that both my PC and a separate laptop had spikes on the  display from
harmonics of the AC power frequency. In the UK we use 50Hz AC power  so that was
present as a very large spike followed by 150Hz and every 100Hz  after that
through the audio spectrum. With your use of 60Hz AC power in the USA  would
possibly expect that plus multiples through the audio test range if  afflicted.
 
The use of an audio isolation transformer killed these spikes stone  dead.
 
Don, W3FPR suggested the audio transformers from scrap PC modem cards as a  
possible source of suitable 600 ohm transformers.
 
The Spectrogram program turned out to have other uses for me beyond  checking
K2s.
Having done a hurried rebuild on a 2m repeater for a semi local repeater  
group, when installed on site the through audio was poor and sounded  muffled.
With the aid of a VHF noise generator plus my laptop running  Spectrogram was
able to follow the audio through from the repeater RX audio  output, through the
logic and right up to the TX modulator. Apart from the  normal RX de-emphasis
and the blocking of the audio below 300Hz in the  logic to remove the
incoming CTCSS, the audio was correct right the way through  the system.
 
The problem in the end turned out to be the TX modulation pre-emphasis was  
not functioning. No doubt there are many other uses for the Spectrogram
program,  but on this occasion saved me a lot of time in fault finding on the  
repeater.
 
Bob, G3VVT
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