[Elecraft] K3, VHF Diversity

[Edward R Cole]

I guess I missed Chuck's posting on Feb.18th.

Harry:

First your question the K3 is unable to operate in duplex as common 
ckts are used in the DSP (2nd IF) for both Tx and Rx.  Only simplex 
operation is allowed.

Chuck:

A couple comments:

I am already doing what you propose as far as receiving dual-pol, 
diversity eme signals:
http://www.kl7uw.com/MAP65.htm

I've posted this on the Elecraft Reflector, before.
I had never considered running it for CW, which is what I think you 
are proposing.  I guess that will work.

You cannot use the 2nd IF to extract IQ baseband if you want to 
connect to digital sw.  To do that you need to tap off both 
receiver's IF into a simple SDR like the LP-Pan feeding a four-port 
soundcard/computer.

Transmitting to both polarity antennas will result in linear polarity 
of 45-degrees or 135-degrees, if split equally.  You would be better 
to add a 90-degree phase line on one polarity to produce circular 
polarization.  That will result in your signal being 3-dB weaker 
received by linear-pol antennas but will suffer no Faraday 
issues.  Several DXpeditions have run this way to avoid dealing with Faraday.

As long as you only run CW you do not need a computer (if you have 
moon pointing pre-printed).

MAP65 requires a computer (of course) and is nearly immune to birdies 
(if not too thick). At present 95% of 2m-eme is digital.

73, Ed - KL7UW
-----------
From: Harry Yingst via Elecraft <elecraft at mailman.qth.net>
To: Chuck Smallhouse <w7cs at theriver.com>,       "elecraft at mailman.qth.net"
         <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] K3, VHF Diversity
Message-ID:
         <243984504.1196890.1424307454407.JavaMail.yahoo at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

I'm curious about this ....
Is it a full duplex system or simplex
(AKA are you listening while transmit?)





       From: Chuck Smallhouse <w7cs at theriver.com>
  To: elecraft at mailman.qth.net
  Sent: Wednesday, February 18, 2015 2:25 PM
  Subject: [Elecraft] K3, VHF Diversity

I am in the process of implementing full diversity reception of 2M CW
EME signals.

I will be using 2 each quad arrays of 2M long yagis,? One
horizontally polarized and the other vertically polarized.? At and
after the antennas' power dividers, there will be installed equal
gain and NF LNAs, followed by equal lengths of Heliax Super Flex down
to the shack.? In the shack will be two identical phase locked
(together) down converters that drive the K3 and it's Sub RX.? This
will result in one polarization in one ear and the other in the
opposite ear.? The TX upconverter and K3, will be locked to the same source.

It will be an interesting on going experiment, to see if/how this
affects and hopefully somewhat overcomes the polarization rotation
and faraday/libration properties of EME received signals.

Also planed, will be to feed both polarizations simultaneously,
during TX, with a QRO+ PA.

BTW, to date I don't use any computer control of the K3 !? I don't
even allow any computers to be on when performing 2M EME operations,
due to the residual broad band noise and birdies emitted by most
.? The availability of a none computer(external) controlled SDR
receiver, among other features, is what sold me on the K3/P3SVGA system.

Chuck,? W7CS



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