John King wrote:
Has anyone else seen this crosstalk?
Yep. I'm sure everyone that's tried it has.
If so, what is considered "acceptable"?
Well, that's harder to answer and entirely dependent upon
your definition of acceptable. Clearly, the K3 wasn't designed
to provide high isolation between the antenna ports - just look
at the unshielded ANT1 and ANT2 leads in close proximity to each
other. If they had been concerned about isolation, these runs
would have been miniature coax (which you could easily install
yourself.)
In the scheme of things, though, the isolation isn't really
too bad. Let's take your case: S3 to S9+20. That's 56 dB of
isolation, which is about what one would expect from a typical
commercial amateur radio grade antenna switch (pay no attention
to the manufacturer's claims - I have measured them.) Isolation
values of 80 dB and up are common in expensive commercial and
military switches (Transco, Narda, etc.)
So, it depends. I knew the port-to-port isolation in my K3 was
going to be less than it could be when I built it. I though about
installing RG-174 in place of the bare wires, but decided not to.
I didn't see where it would buy me anything.
All in all, I love my K3. I'm an engineer, and I've been on the
air for over 40 years. The K3 is a real gem.
73,
john WA1ABI
-----Original Message-----
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net]on Behalf Of Dick Roth, KA1OZ
Sent: Saturday, January 03, 2009 12:14 AM
To: Elecraft Reflector
Subject: [Elecraft] Isolation between Ant 1 and 2??
Hello and Happy New Year!!
Was doing some testing and discovered Ant 1 signal on Ant 2. Ant 1 is
my GAP Titan-DX and Ant 2 is a 100W dummy load.
I was just reading the mail on 75 meters and switched to Ant 2 to test
power. When key was off, I heard part of the QSO that was going on.
While on my dummy load, I was receiving a station S3, which on Ant 1 was
20 over S9.
Has anyone else seen this crosstalk? If so, what is considered
"acceptable"?
--
73,
Dick ka1oz
Middleborough, MA
Radio: Elecraft K3/100(Kit) SN 859
Antenna: Titan-DX
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
Thanks for your input, John. It had been quite a few years before
getting my K3 that I really had my hands in electronic gear. Once I
left the world of two-way radio component-level troubleshooting and
repair work and migrated into microwave radio system-level maintenance
parts of my brain must have atrophied. 56 db really does seem adequate
after all. It all really does have to do with perspective.
By the way...I love my K3! Regardless of the era of ownership (last HF
rig=National NCX-3), it is the finest piece of electronics I've ever owned.
--
73,
Dick ka1oz
Middleborough, MA
Radio: Elecraft K3/100(Kit) SN 859
Antenna: Titan-DX
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
