How to center K1's crystal filters?

[cottersay]

I built my K1 years ago, but I also just re-read the K1 manual, yet I still do not quite understand how to adjust the Xtal filter's bandwidth to center on my chosen sidetone frequency of 500Hz.  (The way I check the K1's xtal filter's center frequency is to display the K1's audio output noise into a PC's spectrum analyzer, as shown below).



How do I adjust FL1, FL2, and FL3's center frequency without messing up any other parameter?

Thank you!

[Don Wilhelm-4]

Unlike the K2, you will not center each of the K1 filters.
Set the K1 IF filter to the narrowest one - FL3 unless you have made
some filter width changes from the normal defaults.
Then adjust the BFO trimmer (C20) to position the center of that
narrowest filter at your chosen sidetone pitch as indicated on your
audio spectrum analyzer.
Then remove the bottom panel and set S2 to the TEST position. Adjust C13
to place the signal at your chosen sidetone pitch - that sets the
Transmit Offset.
Return the S2 switch to the OPR position and you are done.

Make certain you set the menu STP parameter to your chosen sidetone
pitch so you can do SPOT at the same frequency.

The exact center frequency may not track exactly for filters greater
than the most narrow, but will result in a very usable received sidetone
pitch for any of the filter widths.  In other words, the filter width
may increase more on the high audio frequency side than on the low
frequency side, but the peak of the filter will remain at the pitch
obtained by aligning with the filter set to the narrowest setting that
you will use.

73,
Don W3FPR

On 1/25/2016 7:17 PM, cottersay wrote:
> I built my K1 years ago, but I also just re-read the K1 manual, yet I still
> do not quite understand how to adjust the Xtal filter's bandwidth to center
> on my chosen sidetone frequency of 500Hz.  (The way I check the K1's xtal
> filter's center frequency is to display the K1's audio output noise into a
> PC's spectrum analyzer, as shown below).
>
>

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[cottersay]

Thanks, Don!  That's as clear and as concise as I have ever heard;  perfect!  

[Don Wilhelm-4]

The fact that you were using an audio spectrum analyzer of some sort
made my answer easy to state.  The K1 manual does not make any
assumptions about tools like an audio spectrum analyzer, so must resort
to telling you to peak the BFO at your chosen sidetone pitch (or other
words meaning the same thing), and do likewise with the TX offset.  
Since you said you were using an audio spectrum analyzer already, you
provided information that was already halfway to the goal.

BTW, if anyone wants an audio spectrum analyzer to load onto their
Windows PC, I have copies of Spectrogram (both freeware versions 5.17
and 16) local to my website available for download at www.w3fpr.com.  
Look for the links near the bottom of the opening page.  Since those are
copies local to my website, be assured that they have been scanned many
times and are free of viruses (I have reports of other sources of
Spectrogram may be contaminated.  Norton may object because it does not
have enough experience with those downloads, but rest assured, they are
clean and you can ignore the Norton warnings.
SpectrumLab and others will suffice just as well, but I like the
dedicated "scope" display of Spectrogram.

73,
Don W3FPR

On 1/25/2016 7:52 PM, cottersay wrote:
> Thanks, Don!  That's as clear and as concise as I have ever heard;  perfect!
>
>

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[cottersay]

Thanks again Don;  I just downloaded Spectrogram, which is much more dedicated to audio spectrum analysis than my CW Get software (which I mainly use to practice with my straight key and my bug -- the CW Get software cannot be fooled by a bad fist!).

[ktalbott]

You said you built your K1 'years ago'.  Are you sure you have an S2?  If
yours is an early K1 there is no S2, this process is a bit more involved!
Don, can you help with those instructions?  They are not in the current rev
of the manual.
Ken - ke4rg

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of
cottersay
Sent: Monday, January 25, 2016 7:53 PM
To: [hidden email]
Subject: Re: [Elecraft] How to center K1's crystal filters?

Thanks, Don!  That's as clear and as concise as I have ever heard;  perfect!




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[cottersay]

Thanks for the heads up, Ken.  What I know of my rig is that the assembly manual that came with my K1
(Serial# 02652) was printed in January of 2002, and I assembled the K1
sometime in November of 2008.  Ahh, I also see from an old email from
Elecraft that I had ordered a "K1-2 Two-Band 5W CW Transceiver".



On Mon, Jan 25, 2016 at 8:18 PM, Kenneth Talbott [via Elecraft] <
[e-mail]> wrote:

> You said you built your K1 'years ago'.  Are you sure you have an S2?  If
> yours is an early K1 there is no S2, this process is a bit more involved!
> Don, can you help with those instructions?  They are not in the current
> rev
> of the manual.
> Ken - ke4rg
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=7613128&i=0>] On Behalf Of
> cottersay
> Sent: Monday, January 25, 2016 7:53 PM
> To: [hidden email] <http:///user/SendEmail.jtp?type=node&node=7613128&i=1>
> Subject: Re: [Elecraft] How to center K1's crystal filters?
>
> Thanks, Don!  That's as clear and as concise as I have ever heard;
>  perfect!
>
>
>
>
> --
> View this message in context:
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> http://elecraft.365791.n2.nabble.com/How-to-center-K1-s-crystal-filters-tp76
> 13108p7613113.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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[cottersay]

Yep, just checked it out Ken, and the board Rev states that it is Rev. Er, dated 2001.  Hopefully this means that my K1 has the S2 on the bottom of the main board!  I'll soon know (by tomorrow).

[Don Wilhelm-4]

Ken,

You are correct, those K1's without the S2 switch make matters more
difficult for setting the Transmit Offset.
There is a procedure in the older K1 manual which has you short two
solder pads on the RF board to make that adjustment, but it does not
work as well as with the K1's with the switch.

My procedure for adjusting the TX offset on those older K1's is more
complex.
After adjusting the BFO to position the center of the FL3 passband at
the desired sidetone pitch,  I set the K1 to receive a signal at the
same desired pitch.  A signal generator is a handy tool, but an off the
air signal can be used if a signal generator (such as another
transmitter operating into a dummy load) is not available. If using an
off-the-air signal, make sure it does not change frequency - ARRL
bulletins or code practice signals are a stable source of on-the-air
signals.
Receive that signal generator (or on-the-air signal output) on the K1
and also on a separate receiver, and then do a TUNE with the K1 (into a
dummy load).  Adjust the K1 C13 to the same audio pitch that the signal
generator (or on-the-air signal) frequency produced in the monitor
receiver (Spectrogram or other audio spectrum analyzer is helpful in
determining that pitch - any frequency will do - the important thing is
that the audio frequencies are the same).

You can try the procedure in the older manual, and if successful it will
produce the same result, but my test bench is set up with Spectrogram
and a monitor receiver, so the above procedure is the easiest for me.

73,
Don W3FPR

On 1/25/2016 9:16 PM, Ken Talbott wrote:
> You said you built your K1 'years ago'.  Are you sure you have an S2?  If
> yours is an early K1 there is no S2, this process is a bit more involved!
> Don, can you help with those instructions?  They are not in the current rev
> of the manual.
> Ken - ke4rg
>
>

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