[Elecraft] KPA-500 Question

[Dick Dievendorff]

Yes, the band data lines can be paralleled to the KPA500 and another antenna
switching device.  The KPA500 order page offers an optional accessory cable
kit for use with the K3 (KPAK3AUX) that contains of a cable and a "Y"
connector for the AUX connector for just such a purpose. 

The advantage of doing it this way, rather than having the amplifier
involved in antenna selection, is that automated antenna switching is
available whether the KPA500 is on or off.

Band changing with antenna selection can indeed be made automatic. It
requires a little more hardware than the K3 and KPA500. We don't offer a
band decoder of our own, but we work well with the many decoders that are
already on the market.

There are a lot of possibilities when one considers antenna switching
arrangements.  If we offered a 4-position switch, someone would need 6 or 8
or 10.  There are a good number of options available  from a number of fine
manufacturers and there have been a number of construction articles in the
amateur literature.  I'd look first to the NCJ archives if you want to "roll
your own".

73 de Dick, K6KR



-----Original Message-----
From: Fred Maas [mailto:just.one.hill at gmail.com] 
Sent: Sunday, July 10, 2011 11:26 AM
To: Dick Dievendorff
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KPA-500 Question

Thanks for reply.  That is what I thought.

I am not familiar with the various outboard devices to which you refer (as
have never needed them).  I am not suggesting that the KPA500 needs
additional antenna outputs though that is one way to do it.  That would
constritute an internal antenna switch.  The KPA500 represents many upgrades
from my 1980's amplifier so I am surprised that my 80's amp has a capability
that the KPA500 doesn't.

The band data information from the K3 goes to the KPA500 to tell it what
band it is to be on.  Are you saying this can be paralleled safely and also
instruct another device?  I would think such might not be compatible and a
risky thing to do.

In my set up (with an old Yaesu FL-7000) the band data information from the 
K3 goes to the FL7000 to tell it which band to be on.   The FL7000 then 
associates one of four antenna positions with a band, this is changeable at
any time and then remembered, and outputs relay control to a remote antenna
switch.  If the remote switch is not in use, the "antenna" which is
associated by band is irrelevant.  I am surprised that the KPA500 does not
have this capability standard and built in with the outboard remote antenna
relay being an option.  Without this, band changing is not, in fact,
automatic.

73,  Fred


> 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
>