These make it easy:
http://www.ebay.com/itm/4-ea-800-Watt-Hybrid-200-ohm-Load-Resistor-500-mHz-/370454666736?pt=LH_DefaultDomain_0&hash=item5640d19df0#ht_734wt_1396
<http://www.ebay.com/itm/4-ea-800-Watt-Hybrid-200-ohm-Load-Resistor-500-mHz-/370454666736?pt=LH_DefaultDomain_0&hash=item5640d19df0#ht_734wt_1396>
And no, I'm not shilling for Henry Radio. I just buy RF parts from them
here and there. :-)
73,
Jim N7CXI
On 6/14/2012 4:08 PM, mike@n1ta.com wrote:
> A few years ago I built something pretty similar to K4EAA's design,
> which can be found (with great pictures) at:
> http://www.k4eaa.com/dummy.html. Has worked FB for measuring low power
> stuff: mostly the radios before the amp. I have a bigger palstar model
> for amp work, but have often thought of building another homebrew can as
> well, and upping for 2kW or so. I'm sure with some value tweaking it
> could be done easily. The LP version cost me under $40.
>
> Mike N1TA
>
>
> -------- Original Message --------
> Subject: [Amps] Dummy Load Blues
> From: "Jerry Kaidor"<jerry@tr2.com>
> Date: Thu, June 14, 2012 7:54 pm
> To: amps@contesting.com
>
> Hello,
>
> To mess with amps, a good dummy load is a must. I went to my storage,
> and pulled out a Cantenna of unknown provenance that I had purchased
> about
> 30 years ago at a flea market. Not knowing what was in it, I assume it's
> poisonous PCB transformer oil. I had kept the dummy load in a plastic
> bucket
> with a hole for the coax, sealed with coax seal. Now I figured I'd
> dispose of the old oil, clean it out, and put in fresh mineral oil. What
> a mess!
>
> OK, the old oil is gone; it'll be headed to the local hazardous waste
> dropoff. The guts are all washed out in hot water and detergent. The
> heathkit can is toast - rusty and leaking. The silver
> straps around each end of the resistor are broken. So I can reconstitute
> this thing with new silver straps ( luckily I have some silver sheet
> laying around ). And the can - can be replaced with an ordinary one from
> the paint factory. Only trouble with that is - 1 gallon paint cans are
> now *plastic*, not metal. I guess it'll still work, just the heat
> transfer won't be quite as good.
>
> I also scored a 250W load cheap on Ebay. Seller said it came out of a
> cell phone installation. I popped it open - the resistor is the size
> of a postage stamp! I was messing with one of my SB2-LA's, used that
> load - figured a momentary toot from the amp wouldn't hurt it. I was
> wrong. Apparently these little resistors are not only heat limited,
> but *voltage* limited. I hit transmit, there was a small *pop* and a
> puff of smoke. Hole burned right through it.
>
> There are similar load resistors on sale on Ebay - 800W for IIRC $40.
> But that's just the resistor, you have to bond it to a heatsink. I
> have
> the heatsink from the defunct 250W load - I could machine off a big
> enough
> flat spot for the 800W resistor.... failing that, I have a really big
> heat
> sink in my junk.
>
> - Jerry Kaidor, KF6VB
>
>
>
>
>
>
>
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