Topband: RX/TX Antenna switching

[Shoppa, Tim]

I find it ironic that when I was a kid we all built T/R switches to use a single antenna with our separate Transmitter and Receiver.

Today we build a switch to use two antennas to interface with our fancy pants transceivers :-)

1: All but the small or entry level rigs already have a RX antenna input.
2: If you don't have a RX antenna input, then you can put a T/R relay on transceiver output.
3: Relay does not have to be fancy. Small 12VDC relays with contacts rated at several amps work fine (typical street cost, a dollar or two). High power coaxial relays seem completely unnecessary here. Remember at 100W levels the typical RF currents and voltages will be less than a few amps and less than a few hundred V.
4: Amp key line from the rig works well to drive the T/R relay. AFAIK all transceivers since the 1970's have an amp key line.
5: If you have an amp, the T/R relay can sit between rig and amp. This way the relay is only handling the lower power level. Again no need for fancy relays.
6: If (4) you will probably find that you can have QSK on 160M without having QSK in the amp - again gets down to the vagaries of PA vs T/R switch timing. Ironically I use my rigs "amp key" line to key the T/R relay at QSK rate, and my K1EL keyer "PTT" output to key the amp with hang time so its relays do not click on every dit.

Also... on a more interesting antenna switching contest, to switch between multiple receive antennas during a contest, I find it very natural to use footswitches to select receive antenna. This lets me comfortably switch receive directions after every CQ or while scanning the bands in S&P.

And I think I saw you reversebeacon spotted during the contest, but the only YO I worked was YO8DOH.

Tim N3QE

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of cris blak
Sent: Monday, January 28, 2013 5:15 AM
To: topband at contesting.com
Subject: Topband: RX/TX Antenna switching

Hello,

I'm interested to hear from you all, what do you use to switch RX/TX antennas on 160m band.
I'm currently use an INV-L as TX(RX) antenna and a K9AY for RX. 

In this moment I use a high power coaxial manual switch getting through INV-L or K9AY but this is very time consuming, especially in the contest.
I'm thinking of RX/TX switch choosing on RX between K9AY and INV-L and on TX, only INV-L, no metter what is used on RX side. I've tried with a high power coaxial relay but it doesn't work due to faster relays on PA. seems to me that a sequencer should be used.

Look for any practical ideas.

By the way, CQ160mCW contest was a success here with more than 600 QSOs in the log and several DX (also VE/K) stations.

73 de YO3FFF
Cristi
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Topband Reflector