[Boatanchors] Should dummy load oil ever need to be changed?

[Glen Zook]

Collins Radio Company used specially manufactured 7/8ths inch Andrew Heliax that had a Nichrome center conductor for dummy loads on the 20 kW amplifiers.

There was a Dallas YL who bought some of this Heliax from the Collins surplus store and had it installed on all of her VHF antennas.  Of course, she didn't realize that the Heliax was made for dummy load purposes and not for use with antennas.  After having the feedline installed, she couldn't access any 2-meter repeaters but the SWR was great!  She had a friend drive away from her house and he lost her signal less than 3-blocks away!  Needless to say, all that Heliax had to come down and the old feedline re-installed!
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: Ray <w4byg at att.net>
To: boatanchors at mailman.qth.net 
Sent: Saturday, August 25, 2012 12:14 PM
Subject: Re: [Boatanchors] Should dummy load oil ever need to be changed?
 
A useful dummy note note which may interest some:

A piece of coaxial cable open or shorted at the far end with a loss 
rating of about 15 db or more at your frequency of interest, will 
provide a very nice dummy load.  It will provide a return loss of about 
30 db (-15db forward loss and -15db reverse loss) .

If you use a piece of cable rated at about 20 db of loss at your 
frequency of interest, you will have a near laboratory quality dummy 
load (40db RL).

Make sure the cable is rated sufficiently for the power level you are 
going to use it with.