K3EXREF for eme and mw

[Edward R Cole]

Dave,

It hadn't occurred to me that frequency correction would be suspended
in Tx.  That is both good and bad, as I see it.  Good that no phase
jumps occur, but bad that transmitter drift is not being corrected.

For eme digital modes this means the freq. is solely held by the TCXO
over the minute-long transmit sequence.  That probably will not
affect the K3 when running transverters as there will be no large
thermal change in the radio operating at mw levels.  It may see more
effect when I run HF/6m at 12w on my K3/10, but that probably is much
less than those that run the K3/100.

I guess I will have to reserve judgement on how well K3EXREF will
assist operating at microwaves (mw).  As I see it now, the K3EXREF
will track out mid-term frequency drift of the TCXO during receive
sequences, so the Tx drift (if any) is limited to that which occurs
in 1-minute.

Transmitting on CW/SSB is not as exacting on frequency accuracy so
not likely the user will notice a few Hz drift, if it occurs.  Even
used with mw transverters, frequency error remains the same as the IF
error since it is translated in mixing and not multiplied.  Where it
would be significant is if the K3 were used RF source in a Multiplier
chain to produce a mw CW signal.  I am not familiar with what method
is favored for mw >24 GHz

I see REF CAL offsets being applied consistently for the first 30-min
after K3 power-on.  Maybe my TCXO has aged more in the first year of
use?  I saw only 14-Hz freq. error on 28-MHz last fall, while it
shows about 36-Hz error on 28-MHz, now.  This is with no REF CAL
adjustments or K3EXREF running.  Once K3EXREF is initiated 28-MHz
remains within 1 to 2 Hz on my counter.

I will have to monitor 2m when I next run eme to see what happens.

73, Ed - KL7UW

------------------------------

Message: 5
Date: Wed, 6 Apr 2011 07:47:02 -0500
From: "Dave" <[hidden email]>
Subject: Re: [Elecraft] (no subject)
To: <[hidden email]>
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Having done some long term measurements on my k3extref using an HP mHz
resolution counter i have seen no corrections during transmit. Once the k3
has "warmed up" (first thing in the morning it would take 10 minutes for the
original tcxo to stabilise enough for jt65/wspr/qrss(5Hz fsk)) I see very
few corrections being made on receive either.

All I need now is the release of the internal 144 xverter and I am good,
frequency stability wise thro 76GHz

Dave

ww2r




73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 144-1.4kw, 432-100w, 1296-testing*, 3400-winter?
DUBUS Magazine USA Rep [hidden email]
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[Bruce Beford-2]

At first glance, frequency corrections being suspended during transmission
may have a large effect on the usefulness of the upcoming PLL board for the
K144XV. If the frequency is not compensated during TX, when maximum heating
(and therefore freq shift) takes place, it would seem that the K144XV could
still be subject to substantial drift. This would be most true during high
TX time modes like JT65 and WSPR, etc.

I would hope the need for frequency compensation during TX will be
considered and addressed, as the K144XV PLL solution is developed.

Bruce, N1RX

> Ed, KL7UW wrote:

> It hadn't occurred to me that frequency correction would be suspended
> in Tx.  That is both good and bad, as I see it.  Good that no phase
> jumps occur, but bad that transmitter drift is not being corrected.

> For eme digital modes this means the freq. is solely held by the TCXO
> over the minute-long transmit sequence.  That probably will not
> affect the K3 when running transverters as there will be no large
> thermal change in the radio operating at mw levels.  It may see more
> effect when I run HF/6m at 12w on my K3/10, but that probably is much
> less than those that run the K3/100.

> I guess I will have to reserve judgement on how well K3EXREF will
> assist operating at microwaves (mw).  As I see it now, the K3EXREF
> will track out mid-term frequency drift of the TCXO during receive
> sequences, so the Tx drift (if any) is limited to that which occurs
> in 1-minute.




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