One thing I might also add in. I use the Film TO-220 style non-inductive
resistors with a heat sink in the 200 ohm 1% configuration to test 4:1 baluns
at 100 watt level to confirm non saturation on the small QRP baluns I make.
Mel, K6KBE
From: Ron D'Eau Claire <r...@cobi.biz>
To: 'Paul C' <paul...@sbcglobal.net>; elecraft@mailman.qth.net
Sent: Tuesday, December 27, 2016 3:23 PM
Subject: Re: [Elecraft] Dummy loads for dummies
For parts, digikey.com and mouser.com are good friends. No minimum order, great
prices and huge selection.
You've gotten several suggestions for a good dummy load. And I concur with the
others, those wire-wound resistors might be 50 ohms but their reactance may
almost anything and dependent upon frequency. One of the original "Elecrafter
Field Testers" and "F.O.W." - friend of Wayne (Burdick) - was Tom Hammond,
N0SS, no sadly an S.K. But his web site has been maintained and it contains a
great low-cost dummy load design:
http://www.mmccs.com/mmarc/n0ss/dl_30w_hf-uhf.pdf
You might enjoy looking around the web site for more KX1 info and QRP info in
general:
http://www.mmccs.com/mmarc/n0ss/
Coaxial cable is every much as low loss as open wire line when the SWR is not
too high. The difference in applying them is that the inherently
higher-impedance of ladder line makes it much easier to keep the SWR on the
line low enough to avoid excessive loss. For example, a hunk of wire between 50
and 100 feet long strung up in the air and fed at its center will show an
impedance of about 4,000 ohms at the frequency at which it is 1/2 wavelength
long and perhaps as low as 40 ohms on 80 or 160 meters. With open wire line at
about 400 ohms impedance, you will find an SWR of up to 10:1 on the feed line,
generally much less. With 50 ohm coax, the SWR will range as high as 80:1 or
more.
Have fun. At my shack, simple and cheap is great fun!
73, Ron AC7AC
-----Original Message-----
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Paul C
Sent: Tuesday, December 27, 2016 12:23 PM
To: Walter Underwood; elecraft@mailman.qth.net
Subject: Re: [Elecraft] Dummy loads for dummies
Ok, I won't be using these resistors after all. Thanks for setting me
straight.
It seems tuff to get going in QRP. I thought I'd roll my own when possible. I
am trying to keep things simple and economical, the QRP spirit.
Here's another naive idea of mine: I'm planning to use ladder line too. Now
I'm waiting for the other shoe to drop, when I realize coax will be my only
practical choice.
Paul KG5KXG
-----Original Message-----
From: "Walter Underwood" <wun...@wunderwood.org>
Sent: 12/27/2016 1:45 PM
To: "elecraft@mailman.qth.net" <elecraft@mailman.qth.net>
Subject: Re: [Elecraft] Dummy loads for dummies
Ah, yes, bricks. Like these?
https://www.radioshack.com/products/radioshack-100-ohm-10w-10-wirewound-resistor-2-pack#
<https://www.radioshack.com/products/radioshack-100-ohm-10w-10-wirewound-resistor-2-pack#>
wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)
> On Dec 27, 2016, at 11:42 AM, Vic Rosenthal <k2vco....@gmail.com> wrote:
>
> They are undoubtedly wire-wound resistors and will have too much inductance
> to work well as a dummy load. The resistance is fine. If you have an SWR
> meter, check it with that. SWR below about 1.5 would mean it is usable. It
> might be OK on 160 or 80 meters but not on higher bands.
>
> Vic 4X6GP
>
>> On 27 Dec 2016, at 16:43, Paul C <paul...@sbcglobal.net> wrote:
>>
>> I made my own dummy load last night from two 100 ohm resistors wired in
>> parallel. They are rated for 10 watts each and look like little bricks. I
>> measured the resistance at 51 ohms. Do you think this is close enough or
>> should I reduce it to 50?
>>
>> Paul KG5KXG
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