[CQ-Contest] Receive antenna switch

Eric NO3M no3m at no3m.net
Thu Jan 15 04:30:58 EST 2015

See: http://ncjweb.com/features/mayjun12feat.pdf

That is the system I have been using here since the Winter of 2011, 
designed based on requirements for lowband contesting, et.al.

It can handle up to 128 physical antennas to (4) four receivers, which 
in turn are defined as "virtual" antennas in the switching software as 
needed.  Example, an 8-circle BSEF array is (1) one physical antenna, 
but defined as (8) eight separate virtual antennas.  A single physical 
antenna can also be defined as a separate virtual antenna for each 
band.  Each antenna can also be split between receivers, up to 4 ways. 
*** Unused antennas can be user-selectably terminated to open / ground / 
or system impedance, so quite easy to integrate into a reversible bev 
system or dual direction vertical arrays that need terminated lines

The switching units are controlled via an RS-485 serial buss, which 
allows great distances, and uses a simple ASCII protocol. Therefore, 
anyone could spin up software to control it and implement any number of 
features (my boxes having scanning capability with ability to select 
which antennas to incl in scanning, tracking where two different 
antennas are in sync with regard to direction, ie. 8-circle following 
bev selection for diversity) .  I currently use desktop controllers w/ 
microprocessors that store the antenna definitions, etc., and "talk" to 
the switching units, located 600ft from the shack.  There are also 
remote control units with outputs to control circular arrays, switchable 
antennas or other equipment.

In addition, I use signal processing boxes for each receiver line, which 
include preamp, attenuation, TX muting, BCB/bandpass filtering, and 
auxiliary switching blocks.   All these functions are controlled via the 
data buss, so each "virtual" antenna can have it's own gain settings or 
things like filtering, AUX switching, etc., controlled on-the-fly from 
the dekstop controllers.  The processors also monitor the data lines for 
any antenna splitting, and compensate for splitter losses automatically 
by dialing in more gain (or less ATT).  The AUX routing ports are great 
for connecting things like NCC-1 phasing units, LF/MF transverters, or 
any external processing equipment (similar to Elecraft K3 RX IN / RX OUT 
ports). Bandpass filtering is done via W3NQN style receiver filters that 
I designed on T-80 cores.  There is also RX overload protection using a 
COR circuit.

It's quite an easy and obviously extremely flexible system to implement 
from a user standpoint, but currently lacks professional enclosures and 
a nice software interface.  Otherwise, it would fit almost any RX needs 
that I can think of (can even be scaled to M/M).

Anyways... maybe with enough interest it could be something I could get 
motivated to make available.

73 Eric NO3M

On 01/14/2015 11:56 AM, Herbert Schoenbohm wrote:
> I use here a retired Dynair 12X1 passive video switcher.  One nice 
> feature is that each unused RG-6 cable which runs to reversible two 
> wire Beverages is terminated.  With feed line length equal to 1/2 wave 
> (includes the cable velocity factor.) the 75 ohm termination appears 
> at the unused port at the feed box.  The only down side is that the 
> push buttons move a connection on a long bus inside and take a finger 
> pressure.  It would be great if someone would market a desk top remote 
> with momentary light touch switch or with a computer interface.  I 
> have several Ameritron 8X1 along with the RCS 12 but that only gives 
> me 8 positions.  it also does not terminate the unused ports. The 
> DX-Engineering  8X1, (RR-8B) which can be driven by the desktop RCS-12 
> has provisions for unused port termination, but to use a 5KW switch 
> for a bunch of Beverages seems a git of a over-kill.  Hopefully 
> something will be on the market soon as there seems top be a need for 
> something that will control many Beverage inputs.
> Herb Schoenbohm, KV4FZ

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