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
Accurate and known value loads are necessary when measuring power.
Most power meters and measurements are accurate at 50 ohms. Use a
different impedance load or one that has changed value and the power
meter will become one of questionable accuracy.
73
Bob, K4TAX
On 5/1/2019 7:40 AM, Mark Goldberg wrote:
How much do you want to spend?
One of these Bird Termaline series, or similar is the top of the line, but
will cost you:
https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations/500-watts/8201_500-Watt-Oil-Cooled-Terminations.aspx
I was lucky to find a DA412B/U military surplus 600W dummy (similar to Bird
8401) load at a hamfest for cheap.The good ones have N or better connectors
and Hams tend to avoid them. Adapters are not expensive if you want to
connect to PL259s, but I actually use Ns in most of my station. It will
take a continuous key down from my KPA500 with no problem.
73,
Mark
On Wed, May 1, 2019 at 5:04 AM richard gilley <[email protected]>
wrote:
Hi,
Would like a recommendation for a 500 watt dummy load.
Thank you all
Richard AD1G
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