Posted by
gm3sek on
Jul 13, 2011; 7:54am
URL: http://elecraft.85.s1.nabble.com/KPA500-and-KAT500-Ports-tp6574422p6578102.html
Craig Smith wrote:
>I certainly understand the impracticality in terms of cost and size of
>designing the basic KAT500 with a large number of output ports. My
>personal wish is that an optional external Elecraft unit will
>eventually be available that will allow for port expansion based on the
>user's desire for number and configuration. It should be waterproof
>(or easily made so) and controlled by the same bus as the external KAT500.
>
"Waterproof (or easily made so)" is very important because the optimum
location for an ATU is remote from the shack, as close as possible to
the antenna(s) so that the main feedline is operated at low SWR.
Waterproofing requirements vary hugely around the world, and any design
errors will have very expensive consequences, so a designer in
California shouldn't even try to guess what is needed in Scotland, for
example :-). On the other hand, customers in Arizona shouldn't have to
pay for heavy-duty waterproofing that they don't need.
Please let us hope that one version of the KAT500 will be a bare
board-level module that users can package to meet their own
environmental requirements. If anything goes wrong, I'd much rather
blame myself than blame Elecraft.
Returning to antenna switching, most stations will also have a number of
antennas that don't need an ATU. These users may be content with only
two switched outputs on the KAT500 itself, and instead will want to use
a normal 50-ohm remote switch *ahead* of the KAT500.
But look where this discussion is headed... the more antenna switching
possibilities we envision, the less realistic it becomes for the KAT500
to meet them all.
However, there is a half-way solution which could be implemented at
relatively low cost. That is to provide a number of open-collector relay
drivers within the KAT500, remotely configurable through the control
bus. These relay outputs could then be used to create custom antenna
switching arrangements outside of the KAT500. When the KAT500 is
commanded to energize one of its external relay ports, it would know
that a different antenna is being connected to the output of the tuner,
and could then switch to a different bank of stored settings.
This system would greatly expand the flexibility of the KAT500 at very
little hardware cost (no RF-rated parts required, only an addressable
relay driver array and a pin header; all the rest is done in firmware
and the configuration utility). It would also be completely transparent
to anyone who didn't want to use it - they wouldn't even know it was
there.
The key to making this work is to incorporate the external relay drivers
*within* the KAT500 control system. Independent external switching
wouldn't work because the KAT500 wouldn't be aware of it, and would be
continually forced to retune.
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek______________________________________________________________
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