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K2: Problems With PSK

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jperelst

K2: Problems With PSK

I'm having problems with PSK (and other digital modes) on my K2. CW and SSB
seem okay.

Rig
------
K2/100, KSB2, power set to 20 watts. RTTY (Reverse) for PSK.
MFJ-941E Versatuner to a Carolina Windom about 35 ft in the air.
SignaLink USB into an Acer Aspire One running Win XP (SP3)

On 80/75 meters, I can get a 1.2:1 SWR. CW and SSB look good (good forward
power reading on the MFJ). However, with PSK, the best I can get is 5 watts
forward showing on the MFJ, but it needs 5 bars of ALC on the K2. With 1 bar of
ALC I get about 3 watts out according to MFJ.

On 40 meters, I can get a 1.0:1 SWR. CW and SSB look good, and I can get about
8 watts out on PSK with 5 bars of ALC, and about 5 watts with 1 bar.

30 meters is about the same, but with a few more watts, on 20 meters it's still
a few more, etc.

CW and SSB are good on all the bands.

I also tried PSK using SSB (USB) rather than RTTY (Reverse) and got the same
results.

Anybody have any suggestions about where I should start looking to see what the
problem is?

Thanks.

Jon
KB1QBZ
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Don Wilhelm-4

Re: K2: Problems With PSK

Jon,

How do you have the RTTY FL1 BFOs set? It sounds like you are
attempting to use the default settings for the RTTY filter set, and that
will not work well.

Enter CAL FIL (with the internal probe placed in TP2), and first set
RTTY FL1 to the OP1 filter.
Then go to SSB and observe the BFO settings (tap BAND-) for both LSB and
USB (write them down).
Then go back to RTTY mode and set the BFO for RTTY rev to the same value
as the USB BFO, and set the RTTY non-rev BFO to the same value as the
LSB BFO.

That should produce a good signal and a good waterfall display.
The FL1 BFOs are used for transmit in all cases, and RTTY will transmit
through the filter on the KSB2.
FL2 thru FL4 can be set to anything you want because they will only be
used during receive. I normally set FL2 to 1.00, FL3 to 0.70 and FL4 to
0.40, then center those filters at 1000 Hz. Attempting to center them
higher will cause you to run out of BFO range in RTTY normal. The
narrow filters are good for RTTY operation (most others will likely use
the full width OP1 filter) - set the Mark frequency in MMTTY (or other
RTTY app) to 915 Hz and it will allow you to narrow the filters down so
you can avoid QRM (tune with the VFO instead of clicking on the waterfall).

If you have questions about using Spectrogram to set your filters, take
a look at part 3 of the K2 Dial Calibration article on my website
www.w3fpr.com.

73,
Don W3FPR

On 10/10/2010 8:13 PM, Jon Perelstein wrote:

> I'm having problems with PSK (and other digital modes) on my K2. CW and SSB
> seem okay.
>
> Rig
> ------
> K2/100, KSB2, power set to 20 watts. RTTY (Reverse) for PSK.
> MFJ-941E Versatuner to a Carolina Windom about 35 ft in the air.
> SignaLink USB into an Acer Aspire One running Win XP (SP3)
>
> On 80/75 meters, I can get a 1.2:1 SWR. CW and SSB look good (good forward
> power reading on the MFJ). However, with PSK, the best I can get is 5 watts
> forward showing on the MFJ, but it needs 5 bars of ALC on the K2. With 1 bar of
> ALC I get about 3 watts out according to MFJ.
>
> On 40 meters, I can get a 1.0:1 SWR. CW and SSB look good, and I can get about
> 8 watts out on PSK with 5 bars of ALC, and about 5 watts with 1 bar.
>
> 30 meters is about the same, but with a few more watts, on 20 meters it's still
> a few more, etc.
>
> CW and SSB are good on all the bands.
>
> I also tried PSK using SSB (USB) rather than RTTY (Reverse) and got the same
> results.
>
> Anybody have any suggestions about where I should start looking to see what the
> problem is?
>
> Thanks.
>
> Jon
> KB1QBZ
> ______________________________________________________________
> 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
>

______________________________________________________________
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Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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jperelst

Re: K2: Problems With PSK

Don,

Do you ever sleep? It seems as if every time I post something, no matter what
day, no matter what hour, there's a response from you within a few minutes. hihi

Seriously, thanks for your reply.

You had me set the RTTY FL1 BFO about a week ago using Spectrogram.

At any rate, the problem I'm having happens when doing PSK with mode USB as well
with mode RTTY (reverse).

Jon
KB1QBZ

________________________________
From: Don Wilhelm <[hidden email]>
To: Jon Perelstein <[hidden email]>
Cc: elecraft reflector <[hidden email]>
Sent: Sun, October 10, 2010 8:42:59 PM
Subject: Re: [Elecraft] K2: Problems With PSK

Jon,

How do you have the RTTY FL1 BFOs set? It sounds like you are attempting to use
the default settings for the RTTY filter set, and that will not work well.

Enter CAL FIL (with the internal probe placed in TP2), and first set RTTY FL1 to
the OP1 filter.
Then go to SSB and observe the BFO settings (tap BAND-) for both LSB and USB
(write them down).
Then go back to RTTY mode and set the BFO for RTTY rev to the same value as the
USB BFO, and set the RTTY non-rev BFO to the same value as the LSB BFO.

That should produce a good signal and a good waterfall display.
The FL1 BFOs are used for transmit in all cases, and RTTY will transmit through
the filter on the KSB2.
FL2 thru FL4 can be set to anything you want because they will only be used
during receive. I normally set FL2 to 1.00, FL3 to 0.70 and FL4 to 0.40, then
center those filters at 1000 Hz. Attempting to center them higher will cause
you to run out of BFO range in RTTY normal. The narrow filters are good for
RTTY operation (most others will likely use the full width OP1 filter) - set the
Mark frequency in MMTTY (or other RTTY app) to 915 Hz and it will allow you to
narrow the filters down so you can avoid QRM (tune with the VFO instead of
clicking on the waterfall).

If you have questions about using Spectrogram to set your filters, take a look
at part 3 of the K2 Dial Calibration article on my website www.w3fpr.com.
______________________________________________________________
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

Don Wilhelm-4

Re: K2: Problems With PSK

Jon,

Yes, I sleep - you will only rarely see a post from me between midnight
and 8AM local time. I do check my email periodically throughout the day
when I am home, and that is most of the time.

Back to your LSB/USB problem. There should be little difference between
LSB and USB provided the OP1 filter is somewhat symmetrical and is
relatively flat within the passband. You should be able to see that
with Spectrogram. Did the LSB and USB passband shape look about the
same? If not, then the filter is to blame. Check the capacitors to be
certain all are the correct value (CA thru CP). If the capacitors are
OK, then first check the soldering in the filter area (re-flow it with a
hot iron, adding a tiny bit of new solder and flux). If the passband
for LSB and USB are still not close to the same shape, you will have to
change to a new matched crystal set (7 crystals).

Check the carrier balance in both LSB and USB. If you have a 'scope,
you can connect it across the dummy load, and using a sensitive
amplitude setting on the 'scope, plug paddles into the key jack (do not
connect a mic), close the dot paddle and adjust the carrier balance pot
for minimum RF - check both LSB and USB to be certain they are both the
same.
You can use the S-meter of another receiver to make the same check, but
the 'scope is easiest.

If the passband shape for USB and LSB are the same, you should have good
output no matter which sideband is in use.

One temporary "solution" - BPSK does not care which sideband you use
(while others do care), so you can use the one that works well. That
does not fix it, but allows you a bit more operating time.

73,
Don W3FPR

On 10/10/2010 10:22 PM, Jon Perelstein wrote:

> Don,
>
> Do you ever sleep? It seems as if every time I post something, no matter what
> day, no matter what hour, there's a response from you within a few minutes. hihi
>
> Seriously, thanks for your reply.
>
> You had me set the RTTY FL1 BFO about a week ago using Spectrogram.
>
> At any rate, the problem I'm having happens when doing PSK with mode USB as well
> with mode RTTY (reverse).
>
> Jon
> KB1QBZ
>