[Elecraft] KPA-500 Question

[Dick Dievendorff]

Fred:

The KPA500 doesn't have antenna selection, automatic or otherwise.  It has
one input SO-239 connector for the transceiver and one SO-239 connector for
the amplifier output. 

One way to approach this, used by many, is to use the K3 band change lines
on its accessory connector to control an external antenna switch.  Band
decoders are available with varying degrees of capability (and cost)  from
Elecraft (KRC2),  Unified Microsystems (BCD-10) , Top Ten Devices (BD-Y-SD)
, microHAM (Station Master and an earlier Band Decoder) , Array Solutions
(several, their current is called the BandMaster III), and others.  

The Unified Microsystems BCD-10, perhaps augmented with its HSD-9 High Side
Driver Board, is among the most affordable of these.  

Each of the choices has some characteristic that makes it an attractive
solution if it fits your overall station. Some have manual override. Some
provide visual indicators to show the selected antenna.

It's also possible to roll your own, it  can be a simple one IC project for
the decoder chip plus whatever transistors you need to drive your chosen
relays. 

The K3's band change lines go from its back panel accessory connector to the
band decoder.  The decoder controls an antenna switch (a number of relays)
that switches one RF input line to any of N antennas. The list of antenna
switch manufacturers is long and includes microHAM, Top Ten Devices, and
Array Solutions. 

Some multiple-radio stations use a pair of band decoders, one per
transceiver, and a 2 x N antenna switch that allows either radio to use any
antenna, and keeps both radios from selecting the same antenna.  I use an
Array Solutions "SixPak" for this. There are other newer products.

The Antenna1 output of the K3 goes to the KPA500 transceiver in.  The KPA500
output goes to the antenna switch common. The antennas connect to the
antenna switch.

If you're building a multi-radio station with antennas anywhere near one
another, you'd want to add some band pass filters, also automatically
switched, between the K3s and their amplifier(s), to protect the receivers
from the other transmitter(s).

And we call this hobby "wireless"...

Some amplifiers have a couple of antenna outputs.  Ours doesn't.  Whatever
number of antenna connectors we chose, other than one, would be too few for
some and too many for many.

73 de Dick, K6KR

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Fred Maas
Sent: Sunday, July 10, 2011 6:36 AM
To: elecraft at mailman.qth.net
Subject: [Elecraft] KPA-500 Question

something I don't see in the specs of the KPA500, and I wonder if possible
....

the ability to have the KPA500 remember which antenna to associate with
which band, and appropriately switch a remote electronic antenna relay.
Automatic amplifier band switching is of limited usefulness unless the
appropriate antenna is selected automatically at the same time.

Possible or not?

TNX,

73,  Fred - kt5x

K2 # 0700

K3 # 0144

aka W5YA / qrp

aka WS0TA / SOTA
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