[Elecraft] K3 with xmit and receive antennas - advice needed

[Jim Rhodes]

Take a look at MFJ-1707, or HB your own. I built one years ago, but 
never got around to building the receive antennas, so didn't really try 
it out.

Jim K0XU


On 6/9/2010 6:31 PM, Dick Dievendorff wrote:
> John:
>
> You don't have a lot of time before this Field Day, but in the longer term,
> there's a better way.
>
> For this Field Day, I'd look for a manual switch from MFJ or Alpha-Delta or
> something along those lines.
>
> The K3 (and most other radios of recent vintage) provide back-panel "band
> change" or "band level" lines that can be used for this purpose.  The K3
> uses a 4-line (plus ground) BCD encoding on the back-panel accessory
> connector to indicate the band. Yaesu uses the same scheme.  Band decoders
> for this 4-line BCD encoding that are advertised for Yaesu products work
> well with the K3.
>
> ICOM uses a different scheme, but the idea is the same.
>
> Available band decoders for the K3 / Yaesu 4-wire BCD protocol include:
>
> Elecraft KRC2 http://www.elecraft.com/KRC2/krc2.htm,
>
> Unified Microsystems BCD-10  http://www.unifiedmicro.com/decoder.html  See
> the link at the bottom for a more complete description of a simple switching
> system. http://www.unifiedmicro.com/BBCD10_BLK.pdf
>
> Top Ten Devices http://www.qth.com/topten/bdecoder.htm
>
> Array Solutions
> http://www.arraysolutions.com/Products/bandmaster.htm#top%20of%20page
>
> and microHAM http://www.microham-usa.com/Products/band%20decoder.html
>
> The capabilities (and prices) of these devices varies considerably.  Some of
> them have many more functions than just band decoding.
>
> These all help to automate the antenna selection process. You change the
> frequency from the radio front panel (or your logging program on your
> computer), the radio provides signals to the band decoder, the band decoder
> provides +12V to an appropriate set of relays, and the relays select the
> appropriate antenna.  Some antenna relay boxes can switch two radios to N
> antennas, and isolation becomes a very important issue.
>
> There are antenna relay boxes available from some of the same sources. I've
> seen any number of construction articles in QST and NCJ about this.  It's a
> popular station automation topic for contesting stations.  In a contest,
> particularly with guest operators, it's ideal if you can just change the
> radio's frequency and start transmitting, everything else is automated. Some
> of my current antennas require an ATU, and I have to tune my amplifier, but
> I'm hoping someday to automate all that, too.  The really competitive
> stations have all this automated.
>
> You could ask this question on the TowerTalk or CQ-Contes reflector and get
> lots of advice...
>
> 73 de Dick, K6KR
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of John Watkins
> Sent: Wednesday, June 09, 2010 3:33 PM
> To: Elecraft Reflector
> Subject: [Elecraft] K3 with xmit and receive antennas - advice needed
>
> All,
>
> My K3 does not have the option that provides for the third antenna input
> (KXV3).  Would the following method allow me use dual antennas for Field
> Day.  Use the switched 12 volt out to drive an antenna relay to make the
> changeover.
>
> Will this work?  Is there a better approach?
>
> Thanks, John N0EVH
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