All,
Every ham should have a dummy load capable of the maximum power output
of the amplifier IMHO.
The "Cantenna" serves well for the purpose of checking the amplifier
operation and determining if a problem observed is the result of
"RF-in-the-shack" or an amplifier problem.
A precision 50 ohm load is not required for those purposes.
If you intend to do calibration operations, then the "Cantenna" is
"iffy" unless you can be certain it is 50 ohms non-reactive (check with
an antenna analyzer at the frequency of interest).
If you need to do calibrations and make measurements of actual RF
voltages, then you do need a known 50 ohm non-reative dummy load, and
the "cantenna" types likely do not 'hack it'.
73,
Don W3FPR
On 5/1/2019 2:32 PM, Bob McGraw K4TAX wrote:
Those gallon bucket dummy loads, often referred to as "Cantenna" loads,
are inexpensive and generally work OK to a limit. They do have specific
power limitations vs. time such as 1 minute at 1KW. Also, they may not
be 50 ohms. Yes, the label says 50 ohms, but is it? All 3 of mine
measure differently. One as high as 68 ohms. And they change
impedance as they heat. I've purchased all of mine new and two are now
quite old. The 3rd one is 3 years old and has migrated up a few
ohms. Beware of hamfest bargains unless you know what you are buying.
On the other hand and for many more $$$$, the loads made by Bird and
Celwave and other commercial loads are more reliable and accurate. They
also cost a lot more money. And even with these, beware of hamfest
bargains unless you know what you are buying.
Here is a link to the company I've dealt with for Bird products.
https://www.nm3e.com/loadSampler.htm#LoadSampler
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