[Elecraft] Re: [Elecraft]Yet another Dummy Load Idea

[Don Brown]

Hi

I built a dummy load by mounting a chassis mount BNC on a large fender
washer. Then I connected 4 51 ohm resistors in series parallel. (you  could
also use three 5 watt 150 ohm resistors in parallel which would be better)
In other words make 2 sets of parallel connected resistors then connect the
parallel resistors in series. I used 3 watt MOS resistors because they are
non inductive. Connect one end to the center pin of the BNC and run the
other end down to the washer and solder close to the BNC. Then I slipped the
the assembly into a piece of 3/4 inch schedule 40 PVC pipe about 3 or 4
inches long. Now fill the pipe with GE silicone rubber II and allow to set
up overnight. This makes a convenient load and it is good to 15 watts or 25
to 30 for a short time. The silicone forms a heatsink so the resistors will
dissipate a little more than their rating. I have one of the Radio Shack
loads but the home made on works just as will and you don't need a PL-239 to
BNC adapter

Mouser P/N for 5 watt 150 MOS resistor is 286-150 or 51 ohm 3 watt is 283-51

Don Brown
KD5NDB


----- Original Message -----
From: "Ron D'Eau Claire" <rondec@easystreet.com>
To: "'Andrey Stoev'" <ans@vizrt.com>; <elecraft@mailman.qth.net>
Sent: Thursday, November 07, 2002 12:59 PM
Subject: RE: [Elecraft] Dummy load for Part III


> Andrey, it sounds like a dummy load I built many years ago using 2 watt
> 'composition' resistors (not made any longer) for my Viking Ranger.
> Worked FB. Your choice of metal film is the key here from what I
> understand.
>
> The "proof" is easy to test. Check the VSWR of your dummy load. If it's
> reasonably low up through the highest frequency you want to use, you're
> in business. For the K2 that means 1.5:1 or better is fine.  Maybe even
> 2:1 although that's the limit of the acceptable SWR range without
> matching if I recall correctly.
>
> For ops looking for a pre-built dummy load, Radio Shack does make a
> nifty little factory-built dummy load. I bought one 15 years ago to use
> checking VHF radios on ships. It's round, about 1.5 inch in diameter
> (mostly black cooling fins) and about 2.5 inches long with a male SO-239
> coax connector built in one end. It's rated for 15 watts and will handle
> that easily for longer than one should hold the key down on the K2 at
> that power level. The stores don't carry them any longer, but I know a
> fellow who bought one on-line from Radio Shack not too long ago. They're
> about US $20.
>
> Ron AC7AC
> K2 # 1289
>
> -----Original Message-----
> Andrey wrote:
> I am done with my dummy load :-)
> I used male BNC to female PL-259  convertor to attach a PL-259
> T-connector (male with 2 female conectors) to the K2. The dummy load is
> build from the T-Connector, using 20 pieces of 1/2 W 1kOm Resistors.
> First i bended one of the leads of each resistor at 90 degerees, close
> to the body of the resistor, then i used 10 resistors and aranged them
> with all of the bended leads together in a star-shaped pattern (the
> bended leads were in the center and the straight leads were pointing
> away, it looked almost like a flower).
>
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