K3 at KH6LC in Stew Warmup

[Curt Knight]

Aloha,

Considering recent posts, maybe you would be interested to hear about
the setup we used at KH6LC during the Stew Warmup.  I brought my K3 SN
469, which has 2.7, 1.8, and 0.4 filters in the main and matched 2.7
and 0.4 in the sub. Now I know that I should have sprung for the other
1.8 filter and saved myself the labor of installing it later.  Thanks
to the stamina of Ken N6KB we have two beverages, one roughly in the
JA direction and one slightly east of the US mainland direction.  The
transmitting antenna is a shunt fed tower.  We decided to try for
maximum flexibility, so we put the tower on ANT1, the JA beverage on
RX ANT IN and the US beverage on AUX RF.  With the appropriate
configuration via the front panel this put the signals from the
mainland in the right ear and the signals from Asia and Alaska in the
left ear, and if we wanted to try the vertical it was a single button
push to get it. Occasionally a signal would move from ear to ear! The
beverages aren't really very long, the longer is about 450 ft, but
they are surprisingly directional.  I think it's fair to say that this
setup made a positive impression on all of us and now we want Ken to
slog through the jungle some more to put in more and longer wires.
The roofing filter mismatch between 400 Hz and 1800 Hz bandwidth was
sometimes noticeable, but it wasn't a big thing.  One mod I would like
to see would be an option to have the subreceiver bandwidth and shift
track the main as it's an aggravation to have to double click the A>B
when you want that.  Of course, you would like the option of having
them separate, too.

This K3 was the subject of a post last week ("Bad CW Note") and I can
report that this problem seemed to us to not be present last weekend,
but those of you who heard us may tell a different story and if so I
would be happy to hear from you directly.  In between the post and the
weekend, I had partly disassembled the case to look into putting a
strap directly from the antenna tuner RF ground to the rear panel
connectors, but I decided I didn't have the time to finish so I just
replaced the panels, and maybe that improved the ground.  On the other
hand, we did get bad reports on the CW keying.  One report said that
it sounded like the keying was "soft".  Another report said
"distinctive, but not fatally obnoxious".  It appears now that this is
a problem mainly with the computer keying from the rear panel jack,
and not the CW generated from the internal keyer, and that it may be
connected to the TX DLY setting that I had at its maximum value to
accommodate my old TL922 linear.  I have backed the setting off to 15
and the CW weight looks more consistent on my scope now.  At KH6LC
there is a modern linear and the nominal value should be enough.  We
are still looking into this and also the buzz on the note and the
story may change.

Curt AH6RE
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[Bill W4ZV]

Curt Knight wrote

>Considering recent posts, maybe you would be interested to hear about
the setup we used at KH6LC during the Stew Warmup.  I brought my K3 SN
469, which has 2.7, 1.8, and 0.4 filters in the main and matched 2.7
and 0.4 in the sub. Now I know that I should have sprung for the other
1.8 filter and saved myself the labor of installing it later.

<Snip>

>The roofing filter mismatch between 400 Hz and 1800 Hz bandwidth was
sometimes noticeable, but it wasn't a big thing.  One mod I would like
to see would be an option to have the subreceiver bandwidth and shift
track the main as it's an aggravation to have to double click the A>B
when you want that.  Of course, you would like the option of having
them separate, too.

???  What firmware were you using.  Everything in the Sub's DSP should track the Main when in Diversity mode.  Your comment about filters is also confusing.  If you had DSP set to 400 or below, both roofing filters should have been 400 Hz.  If just above 400 Hz DSP, you would have had 1.8k in the Main and 2.7k in the Sub.  If you didn't like the offset effect, you could have disabled the 1.8k in the main so that both 2.7k filters would have been enabled above 400 Hz DSP BW.

>This K3 was the subject of a post last week ("Bad CW Note") and I can
report that this problem seemed to us to not be present last weekend,
but those of you who heard us may tell a different story and if so I
would be happy to hear from you directly.  In between the post and the
weekend, I had partly disassembled the case to look into putting a
strap directly from the antenna tuner RF ground to the rear panel
connectors, but I decided I didn't have the time to finish so I just
replaced the panels, and maybe that improved the ground.  On the other
hand, we did get bad reports on the CW keying.  One report said that
it sounded like the keying was "soft".  Another report said
"distinctive, but not fatally obnoxious".  It appears now that this is
a problem mainly with the computer keying from the rear panel jack,
and not the CW generated from the internal keyer, and that it may be
connected to the TX DLY setting that I had at its maximum value to
accommodate my old TL922 linear.  I have backed the setting off to 15
and the CW weight looks more consistent on my scope now.  At KH6LC
there is a modern linear and the nominal value should be enough.  We
are still looking into this and also the buzz on the note and the
story may change.

You may want to check that the RX ANT port in the KXV3 has had the RX Isolation Mod installed.  If not, you may have been getting RF feedback into the K3 via the RX ANT input.

http://www.elecraft.com/K3/k3_app_notes.htm

73,  Bill  W4ZV

[Bill W4ZV]

Bill W4ZV wrote

???  What firmware were you using.  Everything in the Sub's DSP should track the Main when in Diversity mode.  Your comment about filters is also confusing.  If you had DSP set to 400 or below, both roofing filters should have been 400 Hz.  If just above 400 Hz DSP, you would have had 1.8k in the Main and 2.7k in the Sub.  If you didn't like the offset effect, you could have disabled the 1.8k in the main so that both 2.7k filters would have been enabled above 400 Hz DSP BW.

Just to clarify, see the "###" bracketed comments below:

******************************************************
MCU 2.31 / DSP 1.89, 8-28-08

New Features and Enhancements:
<Snip>
* DIVERSITY RECEIVE MODE: If you have the sub receiver (KRX3 option) installed,
you can take advantage of “diversity receive” by using two separate receiving antennas.
This can improve signal copy during fading, and adds a spatial (L/R) effect to signals.
###DIVERSITY MODE further enhances this capability by slaving the sub receiver’s
mode, filter settings, and VFO to the main receiver.### To enter diversity mode, hold
SUB until you see “DIVRSTY” on VFO B (about 2 seconds). The kHz decimal point
of the VFO A display will flash slowly as a reminder that diversity mode is in effect.
<Snip>
******************************************************

Diversity mode copies Main DSP settings including WIDTH, SHIFT, RIT offsets, etc. to the Sub.  Of course it cannot correct for different XFILs between the Main and Sub, but you can disable any filters in Main that are not in the Sub if desired.  In my case, I have 2.7k/1.8k/500/200 in Main and 2.7k/500 in Sub.  If I set WIDTH to <250 Hz, the 200 will be enabled in Main but only the 500 will be enabled in Sub.  I have personally not noticed any warble when using the 200/500 combination even though the filter offsets differ by 130 Hz (-.91 for the 200 vs -.78 for both 500s).

73,  Bill