K2 power problem with FT8

[Markku Siipola]

I have started to use my K2 for FT8, with the KIO2 digital interface and
the SSB-module. My sound card is connected to the hear phone and
microfon connections. Software WSJT-X, JTAlert and DXLab commander.

On 80m and 40m all is ok, but not on the higher bands. For example on 20
m, the power is reduce very much for certain LF frequences. I tested
this by using the TUNE function in WSJT-X and changing the TX frequence.

LF    Power

400    7
500    3
600    3
700    4
800    7
900    7
1000    7
1100    7
1200    7
1300    4
1400    2
1500    1 <---
1600    1 <---
1700    2
1800    3
1900    5
2000    7

The same problem is also on the remaining high bands

What can be wrong?

73 de SM5FLM



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[gt-i]

Make sure you have no equalizing in the audio output somewhere (that is
important for any transceiver, btw). Also check the SSBA and SSBC
options in the menu, maybe the selected compression ratio is not ideal
for FT8.  See KSB2 manual regarding "PowerControl and ALC".

You could test this with one of the many function generators available
as an app on your smartphone.

This does not explain the band dependency, though. Maybe 80/40 are tuned
good enough to easily achieve the power levels, while the upper bands
are a bit more fragile to produce full output, if not tuned 100% correctly.

73/55 Gernot DF5RF


Am 03.12.2019 um 09:22 schrieb Markku Siipola:

> I have started to use my K2 for FT8, with the KIO2 digital interface
> and the SSB-module. My sound card is connected to the hear phone and
> microfon connections. Software WSJT-X, JTAlert and DXLab commander.
>
> On 80m and 40m all is ok, but not on the higher bands. For example on
> 20 m, the power is reduce very much for certain LF frequences. I
> tested this by using the TUNE function in WSJT-X and changing the TX
> frequence.
>
> LF    Power
>
> 400    7
> 500    3
> 600    3
> 700    4
> 800    7
> 900    7
> 1000    7
> 1100    7
> 1200    7
> 1300    4
> 1400    2
> 1500    1 <---
> 1600    1 <---
> 1700    2
> 1800    3
> 1900    5
> 2000    7
>
> The same problem is also on the remaining high bands
>
> What can be wrong?
>
> 73 de SM5FLM
>
>
>
> ______________________________________________________________
> 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]

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[Don Wilhelm]

How old is this K2?  Those K2s with Serial Numbers below 2560 have the
original IF crystals.  You will achieve a flatter passband if the
crystals on the KSB2 board (and the RF Board) are replaced with the
upgrades crystals.

If your KSB2 card is older, check the resistors on that board against
the newer schematic to be certain the PSK mod has been added to that
option board.

Make certain the filter alignment is done correctly and that the OP1
filter is selected for the FL1 filter.

Do a complete filter alignment using a visual aid like an audio spectrum
analyzer like Spectrogram running on your computer and a broadband noise
source (like the Elecraft N-Gen) connected to the K2 antenna.  You can
find Spectrogram on my website www.w3fpr.com - scroll down on the home
page to near the end.

Don't overlook the possibility that your soundcard may not be producing
a flat response.

73,
Don W3FPR

On 12/3/2019 3:22 AM, Markku Siipola wrote:
> I have started to use my K2 for FT8, with the KIO2 digital interface and
> the SSB-module. My sound card is connected to the hear phone and
> microfon connections. Software WSJT-X, JTAlert and DXLab commander.
>
> On 80m and 40m all is ok, but not on the higher bands. For example on 20
> m, the power is reduce very much for certain LF frequences. I tested
> this by using the TUNE function in WSJT-X and changing the TX frequence.
>
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[Don Wilhelm]

I should add that you should drive the K2 audio sufficiently, then
adjust the power knob for the desired power output.
Attempting to use the audio level to adjust the power output will result
in "Power Hunting" and could be the cause of some of your problems.
The proper audio level for the K2 can be determined by watching the ALC
indication on the LED bargraph.  Set the DISPLAY to indicate ALC, then ---
Increase the audio until you have the rightmost bar flashing, and then
reduce the audio until it just goes out.

The K2 gain may be different for each band due to changing gain in the
RF Chain with frequency.  So you may have to adjust the audio level for
each band.

If you are using SSB mode, make certain that SSBC is set to 1-1 to
assure no compression.  You can turn the RTTY filter set on and align
that filter set.  The SSBC setting is independent of that used for SSB
so you can leave your SSB compression setting in place.

73,
Don W3FPR
-------------------------------------------------------------------------------------------------------------------------------
How old is this K2? Those K2s with Serial Numbers below 2560 have the
original IF crystals. You will achieve a flatter passband if the
crystals on the KSB2 board (and the RF Board) are replaced with the
upgrades crystals.

If your KSB2 card is older, check the resistors on that board against
the newer schematic to be certain the PSK mod has been added to that
option board.

Make certain the filter alignment is done correctly and that the OP1
filter is selected for the FL1 filter.

Do a complete filter alignment using a visual aid like an audio spectrum
analyzer like Spectrogram running on your computer and a broadband noise
source (like the Elecraft N-Gen) connected to the K2 antenna. You can
find Spectrogram on my website www.w3fpr.com - scroll down on the home
page to near the end.

Don't overlook the possibility that your soundcard may not be producing
a flat response.

73,
Don W3FPR

On 12/3/2019 3:22 AM, Markku Siipola wrote:
> I have started to use my K2 for FT8, with the KIO2 digital interface
> and the SSB-module. My sound card is connected to the hear phone and
> microfon connections. Software WSJT-X, JTAlert and DXLab commander.
>
> On 80m and 40m all is ok, but not on the higher bands. For example on
> 20 m, the power is reduce very much for certain LF frequences. I
> tested this by using the TUNE function in WSJT-X and changing the TX
> frequence.
>
______________________________________________________________
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