[Elecraft] KPA-500 Question

[Fred Maas]

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
>