[UK-CONTEST] 2x6 Antenna Switch

[Cooper, Stewart]

Hi Jim,
I made my own antenna switcher. It handles 2 radios, 6 antennas, auto switches, and prevents simultaneous operation on the same band. I used Maplin relays which cost me about £5 each. My design only required 12 relays. I use it for SO2R, but I have used it in a Multi-2 operation. I still have some cross-talk between 20, 15 and 10 in some combinations, but I live with it - 20m breakthru on 10m is worst. I run an Alpha 91b on the left and a Collins 30S1 on the right, and the arrangement has handled the power without a problem for about 4 years.
I use two http://www.unifiedmicro.com/decoder.html band decoders. I use ICE auto-switching band-pass filters and also stubs on some bands. I can over-ride the auto band switching, with a 2 x 6 way push button switch bank (that cost me a fiver at a rally). The relay unit is built into an old metal chassis/box, which could be made water-proof and put outside I suppose.
All in all I am very happy with the whole arrangement and ignoring the ICE filters, it hasn't cost much. You need the filters though, and the stubs really do help too. This would apply even if you purchse a Six-Pak. It was not a challenge to build.
I would be happy to put the relay switching arrangement down on paper if you want a copy. In fact, I might get inspired and put the whole thing on my website of there's any demand. I've never actually drawn out the circuit, but it is quite clever (thanks to GM4ZUK, not me), and could be expanded to more antennas and radios very easily, as it works on a matrix arrangement.
73
Stewart
GM4AFF


-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com]On Behalf Of Jim Martin
Sent: 05 June 2006 20:22
To: uk-contest at contesting.com
Subject: [UK-CONTEST] 2x6 Antenna Switch


I am looking to build a six antenna to two radio switch box.  I cannot
justify a commercial unit at £300+.  Having only two antennas at the home
QTH it will only be used when out portable contesting (that is until we buy
our Highland B&B and build a huge antenna farm!!)
Two articles I have found so far are http://www.qsl.net/ei7ba/remote.htm
from John's excellent site and
http://www.qsl.net/k5lxp/projects/CoaxSwitch/CoaxSwitch.html which is very
close to what I am after.  With this design I could complete the project for
about £120, using 5amp relays from Maplin. (P/No. QC82D rated 240v X 5amp =
1200w, maximum output at the moment is 100w and hopefully these relays would
cope with 400w in the future?)
I have a slight concern using this in a multi-op environment. If an antenna
is in use by station A it cannot be selected by station B which saves me
sending 100w into the other rig. Unfortunatly this rig is then left without
an antenna and is shorted to ground.  Disaster if the operator is not paying
attention to antenna selection.  Are there any newer designs  which address
this problem or have additional input from the band decoders?
The current set up is 2 x MP-STUBS relay switched controlled by band
decoder-auto BPF controlled by band decoder-antenna(soon to be 2x6 switch
box, manual control)
Having spent years keeping the coax and antennas from two stations as far
apart as possible I am feeling a bit anxious at having both 100w outputs
within a few inches of each other on a PCB!  Is there anything specific I
need to do to ensure isolation of the two signals and a restful nights
sleep?
Are there better relay options?  I will need 20 in total as I need to build
a new stub switching unit.
As always your thoughts and advice would be appreciated.
73
Jim,  MM0BQI


_______________________________________________
UK-Contest mailing list
UK-Contest at contesting.com
http://lists.contesting.com/mailman/listinfo/uk-contest

Scanned by IFB SafeMail http://www.ifb.net for virus content.
IFB Spam-Score:whitelisted

----------------------------------------------------------------
   
Offshore Design Ltd
   
www.odl.co.uk
   
This email is for the sole use of the intended recipient(s) and may contain confidential
and privileged information. You should not disclose its contents to any other person. Any
unauthorised review, use, disclosure or distribution is prohibited. If you are not the
intended recipient, please notify the sender immediately.