[Elecraft] Synthesizer Issue

[Edward R Cole]

In a couple e-mail exchanges off the reflector (with David) I 
realized that I did not fully describe how diversity reception is 
being used on eme (for adaptive dual-polarity reception).  I know 
this out of the area of most interest on this list so bear with me:

I forgot to say that using diversity reception with the K3 for eme, 
the receiver (VFO-A) is set to a single frequency and not 
moved.  Typically on 2m-eme this is 144.125 MHz.  The K3 is placed 
into diversity reception and Tx SPLIT is engaged so that VFO-B 
controls transmit frequency.  Changing Tx frequency is done with 
VFO-B which does not affect the diversity Rx.

This is used for digital eme modes so the K3 is run in DATA-A (USB) 
mode to interface with a computer soundcard.  Special SDR sw (MAP65) 
is run on the computer which decodes received signals and generates 
the transmit digital signal.

Receive tuning is done in the sw on the computer (VFO-A is not moved 
from 144.125).  The sw displays up to 90-KHz of the band (like a 
panadaptor) and receive frequency is selected using the computer on 
the digital frequency span display.  So the receiver VFO is not moved 
to tune within this sub-band and all frequencies preserve the same 
phase relationship in both receivers in the K3.  Rx tuning is done in 
DSP and not in the K3.

Note: that I do not use the internal DSP (2nd IF) of the K3, but tap 
off the 1st IF to two phase-locked LP-Pan to generate two IQ baseband 
audio streams which are converted to digital by a special four-port 
soundcard (M-Audio Delta-44).

This is quite different on how most use diversity Rx (where one tunes 
VFO-A for different signals).

73, Ed - KL7UW
PS: as far as I am aware, I have the only dual-pol adaptive eme Rx 
that utilizes the K3/KRX3 combo.  Other stations use dual channel 
SDR's such as the HB9DRI IQ+ receiver.

-----------------
Date: Tue, 3 Mar 2015 22:21:13 +0000
From: David Anderson <gm4jjj at yahoo.co.uk>
To: Wayne Burdick <n6kr at elecraft.com>
Cc: elecraft <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Synthesizer Issue
Message-ID: <E456211E-DC8B-4EA5-9FB2-C5C4DEBF095A at yahoo.co.uk>
Content-Type: text/plain;       charset=utf-8

Wayne,

For folks that were using the two receivers for VHF EME polarity
diversity reception over a wide bandwidth with MAP65 software, where
they would have gain and phase matched preamps this must be an
improvement for them.

I think it was not generally understood that the absolute value of
the phase relationship of the receivers would change as the VFO was
moved. The only person I know that is currently using his K3 for
doing this is Ed KL7UW, so he may be interested in this.

73

David Anderson GM4JJJ
snipped--------

 > With the original synths, moving the VFO even a small amount
causes both the main and sub synths to be updated. Since they use
separate LC oscillators, the phase relationship will change. The two
will remain phase-locked to the reference, but the absolute value of
the phase between the two synths will be some value between 0 and 180 degrees.

  > 73,
  > Wayne
  > N6KR

73, Ed - KL7UW
http://www.kl7uw.com
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