K3 + XV-144 use on EME

[WD6DBM]

Dear Elecrafters:

This weekend I put my new K3 + XV-144 on EME using JT65 for the first time.  I have these questions:

1.  Using USB, I got a 20% TX power fluctuation depending on the tone being sent.  By going to TX ESSB, this is reduced to about 10-15%.  Is there a way to even out the TX power?  My previous rig (TS-2000) would send the various tones with only a few watts (out of the 500w amp) variation.  I tried compression as well, but it didn't help much at low compression settings.  I also tried the TX EQUALIZATION but I think the bands overlap the tones.  What's the best strategy here?

2.  The first station I worked off the moon reported my TX signal being abt 600 Hz high.  My XV-144 has the xtal oven and had been on for an hour before I got on the air.  I was able to dial this in using XVTR OFFSET, but I had to set it to +600 to move the signal down 600Hz.  Shouldn't this work the opposite way?

3.  While monkeying with the XVTR OFFSET, both VFOs locked on the K3, every time I would change the parameter and exit the menu VFO A would be set to 144.200, and the preamp would be on when I had turned it off and set the attenuator.  Is this a possible firmware issue?  It would be easier to fiddle with XVTR OFFSET if these other parameters just stayed locked.  By working several stations of known frequency accuracy, by subtracting the calculated Doppler shift from the actual frequency difference I managed to get the XV-144 pretty close in frequency I think.

Did I mention I LOVE THIS RIG!

Thanks and 73

Eric WD6DBM
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[wayne burdick]

On Mar 8, 2009, at 9:23 PM, eric norris wrote:

> This weekend I put my new K3 + XV-144 on EME using JT65 for the first
> time.  I have these questions:
>
> 1.  Using USB, I got a 20% TX power fluctuation depending on the tone
> being sent.

Hi Eric,

The K3's 8-pole, 2.8 kHz filter has typically less than +/- 1 dB
ripple. The 5-pole 2.7-kHz filter can be higher. "20%" power
fluctuation is only 1.5 dB, so this could entirely account for what
you're seeing. It may be possible to compensate using TX EQ, but it
would be more accurate to compensate directly at the DSP's IF, which is
on our list for future consideration.

Does the present amount of amplitude variation affect JT65's accuracy?

>
> 2.  The first station I worked off the moon reported my TX signal
> being abt 600 Hz high.  My XV-144 has the xtal oven and had been on
> for an hour before I got on the air.  I was able to dial this in using
> XVTR OFFSET, but I had to set it to +600 to move the signal down
> 600Hz.  Shouldn't this work the opposite way?

Yes. In the XVn OFS menu entry, you're telling the K3 how far off your
transverter is, and in what direction. The K3 compensates the VFO for
this.

>
> 3.  While monkeying with the XVTR OFFSET, both VFOs locked on the K3,
> every time I would change the parameter and exit the menu VFO A would
> be set to 144.200, and the preamp would be on when I had turned it off
> and set the attenuator.  Is this a possible firmware issue?

Maybe. Please give me the exact series of K3 switch/knob events so I
can try to duplicate it.

> Did I mention I LOVE THIS RIG!

Yes :)

Thanks!

73,
Wayne
N6KR

---

http://www.elecraft.com

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[Joe Barger]

HI Wayne,

I have also noticed about the same TX power fluctuation when running JT65B
with the K3 + XV-144 and attributed it to the filter variations.  Normally
20% isn't much of a problem, but when working a very weak signal mode like
JT65B having the tones vary 1.5 db could make a significant difference in
decoding a sequence or not.  In my case, full power output occurs at the
lowest tone (1270 Hz) declining to about 20% lower at the highest tone
(~1625 Hz).  I believe the ability to accurately compensate at the DSP's IF
would be a valuable addition.

73

Joe N6KK

PS.  I didn't mention it, but I LOVE THIS RIG!


----- Original Message -----
From: "wayne burdick" <[hidden email]>
To: <[hidden email]>
Cc: <[hidden email]>
Sent: Sunday, March 08, 2009 10:15 PM
Subject: Re: [Elecraft] K3 + XV-144 use on EME

>
> On Mar 8, 2009, at 9:23 PM, eric norris wrote:
>
>> This weekend I put my new K3 + XV-144 on EME using JT65 for the first
>> time.  I have these questions:
>>
>> 1.  Using USB, I got a 20% TX power fluctuation depending on the tone
>> being sent.
>
> Hi Eric,
>
> The K3's 8-pole, 2.8 kHz filter has typically less than +/- 1 dB
> ripple. The 5-pole 2.7-kHz filter can be higher. "20%" power
> fluctuation is only 1.5 dB, so this could entirely account for what
> you're seeing. It may be possible to compensate using TX EQ, but it
> would be more accurate to compensate directly at the DSP's IF, which is
> on our list for future consideration.
>
> Does the present amount of amplitude variation affect JT65's accuracy?
>
>>
>> 2.  The first station I worked off the moon reported my TX signal
>> being abt 600 Hz high.  My XV-144 has the xtal oven and had been on
>> for an hour before I got on the air.  I was able to dial this in using
>> XVTR OFFSET, but I had to set it to +600 to move the signal down
>> 600Hz.  Shouldn't this work the opposite way?
>
> Yes. In the XVn OFS menu entry, you're telling the K3 how far off your
> transverter is, and in what direction. The K3 compensates the VFO for
> this.
>
>>
>> 3.  While monkeying with the XVTR OFFSET, both VFOs locked on the K3,
>> every time I would change the parameter and exit the menu VFO A would
>> be set to 144.200, and the preamp would be on when I had turned it off
>> and set the attenuator.  Is this a possible firmware issue?
>
> Maybe. Please give me the exact series of K3 switch/knob events so I
> can try to duplicate it.
>
>> Did I mention I LOVE THIS RIG!
>
> Yes :)
>
> Thanks!
>
> 73,
> Wayne
> N6KR
>
> ---
>
> http://www.elecraft.com
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html
>

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