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Re: Topband: Voltage along coax feeder

To: topband@contesting.com
Subject: Re: Topband: Voltage along coax feeder
From: donovanf@starpower.net
Date: Thu, 28 Mar 2013 11:18:09 -0400 (EDT)
List-post: <topband@contesting.com">mailto:topband@contesting.com>
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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