Its very wise to use an isolation transformer -- at least at the receiver end
-- so a shorted capacitor can never result in a blown radio front end! As W8JI
has pointed out, be very careful to take precautions to prevent water and
moisture infiltration into your coaxial cables and connectors which can result
in an elevated noise floor.
As KM1H reminded us, very inexpensive 24 volt microwave SPDT RF relays sealed
in a DIP package from Electronic Goldmine are superb high isolation relays for
receiving antennas. It takes only 8 milliamps to drive the coil. I've never had
a relay failure.
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16510
73
Frank
W3LPL
----- Original Message -----
From: "Tim Shoppa" <tshoppa@wmata.com>
To: "David Cole" <g3rcq@yahoo.co.uk>, topband@contesting.com
Sent: Wednesday, March 27, 2013 2:32:25 PM
Subject: Re: Topband: Voltage along coax feeder
September 1997 QST, K9AY relay and switch box.
Usually done with two DPDT relays (giving 4 possible permutations) rather than
three SPST relays.
Google will find you many slight variations of the remote relay and station
controller boxes showing different ways to couple in the control voltage over
the coax. Some use chokes others use transformers. Some use autotransformers
and some use isolation transformers. I use isolation transformers at both ends
of CATV 75 ohm coax.
Tim N3QE
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of David Cole
Sent: Tuesday, March 26, 2013 4:49 PM
To: topband@contesting.com
Subject: Topband: Voltage along coax feeder
Could anyone please point me in the direction of a circuit to feed +12 -12 and
AC along the feeder to my beverages to switch 3 relays - thanks all from Dave
in the UK All good topband ops know fine whiskey is a daylight beverage.
_________________
Topband Reflector
All good topband ops know fine whiskey is a daylight beverage.
_________________
Topband Reflector
All good topband ops know fine whiskey is a daylight beverage.
_________________
Topband Reflector
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