Roger:
The topic is extremely timely. I expect there are a lot of Cantennas still
floating around out in Hamdom. One is tempted to naively treat it like a
precision 50 Ohm RF load.
I measured the DC resistance of mine with a DMM and the reading was 46.1
Ohm. I dimly recall doing some noise bridge readings at various HF ham
frequencies a few months back, and it seemed to me that the readings all
came out reasonably close to 50 Ohms. When things quiet down, I suppose I
should revisit the readings with a bit more of a critical eye.
I do not dispute than many Cantennas eventually evolve into a 68 Ohm load.
I built mine in 1977 (it is only 28 years old and not 30 as I said
earlier). I was inactive from 1983 through 2004. When I have been active it
has been mostly QRP and never above 100 W. Thus, I never really got the
puppy hot, and that may explain why the resistance is still close to 50 Ohms.
For what its worth, the resistor has been continuously immersed in oil, and
I have never changed the oil since I built the device.
BTW. Does anybody know if the reactance also tends to creep with age/use? I
cannot think of a good reason why it should, but RF properties are strange.
73,
Steve
AA4AK
At 01:10 PM 2/9/2005 -0800, you wrote:
Steve,
Regarding the Heath Cantenna....I have been scratching around with power out
readings recently and after a search of the archives for the word "cantenna"
yeilded some intersting results.
What I thought over all these years (since 1964) a 50 ohm load was actually
a
68 ohm load after many years in oil and many heating cycles.
Thought that topic would be timely again here on the reflector.
Roger WA7BOC K2#755
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