[Elecraft] 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" <elecraft at g4fre.com>
Subject: Re: [Elecraft] (no subject)
To: <elecraft at mailman.qth.net>
Message-ID: <PHEOJOHBIKMLJJHHFCGFKEAMEBAA.elecraft at g4fre.com>
Content-Type: text/plain;       charset="us-ascii"


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 dubususa at hotmail.com
======================================