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Dummy Load plans and pics please ;) My Cantenna finnaly rotted through :(

WINKDOGG

WINKDOGG

President CFO & CPFO WorldwideDX Radio
Feb 21, 2011
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Like the title says I had a very old rusty Heath-Kit 1000 watt Cantenna dummy load but it finally started leaking and showed a dead short ;( I disposed of it for obvious reasons but im mad I did not pop the lid and keep it for a rebuild ;( . I have found some plans and they are ok but Im just wondering should I buy a new one , a kit , or scratch build one ? I ran the cantenna for 20+ years with a gallon of transmission fluid in it and it was great but the time has come for a fresh dummy load ! I have seen some salt water diy loads but mostly rated around 200 watts at 50 ohms . Im looking to build a 1500-2000 watt peak dummy load from the parts pile ! If its just cheaper tom buy one , guess what I may still build my own lol

Any links , thoughts or ideas would be great ! Im hoping to get a nice set of plans and I will do a build video and post it for all to see ! I have a shiny new 1 gallon paint can , pl259 chassis connector as well as assorted high power resistors , solid copper wire , and all types of goodies to build it with but would like a tried and true setup I know I can trust!

Thanks again as always , 73's 4-2-Zero Brian in NJ
 

https://www.ebay.com/itm/1650W-50Oh...969872?hash=item2f0518bb90:g:UO8AAOSwaP5cm0rk

I think it goes without saying that you would need a YUUUUUGE heatsink.

Note: Because of the need for a good sized flange for a heat path the possibilities for more economical 50 Ohm parts in series/parallel are limited by total capacitance. It might be better to simply series resistors and use a broad band transformer for higher wattage. This has the additional advantage of placing a high wattage 4:1 or 6:1 transformer in the shack for other purposes .
 
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Dmans said:
WINKDOGG,
Build your own but use mineral oil in it. (Available from a drug store)
Or keep a fire extinguisher handy!

Good Luck

73
David
Click to expand...

You will get a lot of strange looks from the cashier if you buy a gallon at a drug store,..... and pay waaaaaay to much.
Walgreens 16 oz for $6.00.. about$45/gal

Get it from an Ag. type store like Tractor Supply,...... its a lot cheaper ($20.00/gal) and they sell it by the gallon all the time.
 
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kopcicle said:
https://www.ebay.com/itm/1650W-50Oh...969872?hash=item2f0518bb90:g:UO8AAOSwaP5cm0rk

I think it goes without saying that you would need a YUUUUUGE heatsink.

Note: Because of the need for a good sized flange for a heat path the possibilities for more economical 50 Ohm parts in series/parallel are limited by total capacitance. It might be better to simply series resistors and use a broad band transformer for higher wattage. This has the additional advantage of placing a high wattage 4:1 or 6:1 transformer in the shack for other purposes .
Click to expand...
$130.00 FOR ONE RESISTOR? Buy the new CanTenna for $45.00 of $50.00.(Very old price)
 
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If you really must do it yourself. The video I posted above is a design that works perfectly fine, and as far as I know, is very similar to the Heathkit can internals. I never had mine open. That 100W, 50 Ohm, carbon rod resistor will handle 1000W ICAS when submerged in mineral oil, no problem at all. Those resistors are pretty cheap too if I'm not mistaken. Unless you're doing high power VHF or UHF, it's doubtful that you need any type of specialty resistor.
 
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kopcicle said:
https://www.ebay.com/itm/1650W-50Oh...969872?hash=item2f0518bb90:g:UO8AAOSwaP5cm0rk

I think it goes without saying that you would need a YUUUUUGE heatsink.

Note: Because of the need for a good sized flange for a heat path the possibilities for more economical 50 Ohm parts in series/parallel are limited by total capacitance. It might be better to simply series resistors and use a broad band transformer for higher wattage. This has the additional advantage of placing a high wattage 4:1 or 6:1 transformer in the shack for other purposes .
Click to expand...


That's crazy. I bought two 100 ohm 800 watt resistors for twenty-something each off Ebay. Less than $50 for the pair delivered.
 
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My original Heathkit can top and resistor are now in its third new can of oil after 40 years. The can takes about 20 years for the bottom to rot out depending on humidity in your shack. Oddly enough, it's drifted down in value to about 45 ohms after all this time. It's the one that was used with the least regard to rated specs... Still close enough to use for most applications.
 
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This thread made me check my Cantenna bottom, not sure I ever have since buying it from a hamfest. Looks like the bottom of mine may have leaked in the past and someone soldered it closed?

Mine was cheap and although the guy said it worked fine, when I got home the resistor measured 80 or 90 ohms and did not give a good SWR at all, makes sense if it leaked and was ran like that. I installed 20 1-watt carbon resistors just to use it (that I already had), but they have held up to abuse over the years. I think the biggest amp I ran into it was a Maverick 250, lots of other smaller amps, have not fried the resistors yet.

The top lid looks reasonably okay, so if it does leak I'll just swap the can. I'm in the process of moving and happened to have this on the basement steps and wanted to see if the bottom was rusty.

I'll have to make sure I keep an eye on this for leaks, something I never thought about before to be honest.

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IMG_2820.JPG
 
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