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

[Wayne D Anderson]

Gentlemen

It seems to me that in a hobby that found the use of a lightbulb as an acceptable  load, the Cantenna looks like a pretty good alternative. 

73
K7WDA



Wayne D Anderson 
Designated Broker 
Via Realty 
Tucson AZ 
www.viarealty.com 
(520) 327-1550
 



-----Original Message-----
From: Drew P. <drewrailleur807 at yahoo.com>
To: boatanchors <boatanchors at mailman.qth.net>
Sent: Sat, Aug 25, 2012 8:01 am
Subject: Re: [Boatanchors] Should dummy load oil ever need to be changed?


Brian wrote:
(snipped)
"The Heath Cantenna uses a carbon resistor (good) in a parallel sided tube
very bad). What this means is that as a dummy load, the main dummy is the
ser. In a word, the Heath Cantenna is, in this format, only good for DC.
he air-surrounded MFJ jobbie is just as useless. For a proper dummy load
ook for a Bird Termaline.
If you have a friend with a very good lathe, get a negative exponential cone 
urned up to house the carbon resistor - then it will have performance flat 
eyond at least 1 GHz. I have designed such a cone, used one surrounding that 
elf same carbon resistor and achieved the performance I specified at least up 
o 500 W."
How good does the dummy load have to be?
Yes, the performance of the Cantenna deteriorates as frequency increases.  It 
ould be most useful at lower frequecies - HF region.  In its use, one might 
eclare and not go above a "cutoff frequency" at which the VSWR has risen to an 
bjectionable level, say, 2:1. 
On the same topic, Rob wrote:
> Now, having written all that, let me also add that for AM the Cantenna
 is inadequate in my opinion, except for brief test transmissions.
 That sucker will get hot if you dump a carrier into it for more than a
 minute or two, especially over 300 watts.  Use it, but keep looking
 for something better.
I like the idea of a big salt water dummy load - easy to build and cheap. A 
oogle search turned up this link and many other references.
http://www.deserthound.com/amateur-radio/rfdl01.html   
(Salt water dummy load text is at the bottom of the referenced page.)

rew
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