I have heard the same thing about the original Heath Cantenna.
I have a homebrew gallon size "Cantenna" that I built many years ago. I
happened along some large wattage carbon resistors (about 1/2 inch in
diameter and 2.5 inches long - maybe 25 watts each) and used several of
them in parallel to create a 50 ohm load ( I recall it was 11 560 ohm
resistors). This was when I was a "cash-flow restricted ham". I
measured mine recently with my antenna analyzer and was surprised to
find it was still less than 1.15 SWR up through 30 MHz. This is despite
reports that the old 'trusted' carbon carbon resistor changed value with
age. In any case, I am happy with the results of that old homebrew
dummy load.
In the same batch of resistors, I also had many 1500 ohm units. I was
going to put 30 of them in parallel for a dry dummy load, but the lead
length was excessive and the leads gave it an inductive characteristic
above 14 MHz.
The original Cantenna used a single resistor which apparently did change
in value with aging.
73,
Don W3FPR
On 3/24/2015 6:44 PM, Dave KW4M wrote:
It's a good idea to check the resistance of any used dummy load, especially
one that has some age on it.
The resistance of my 30+ year old Heath Cantenna gradually reduced to 42
ohms. This was enough error for the power meter to indicate a potential
transmitter problem.
W1GA is selling non-inductive replacement resistors on eBay for use in the
Cantenna. I purchased one and it brought the resistance back to 50 ohms.
-----
Dave
My Web Site
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