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QRP Dummy Load

JEV

Mr. Congeniality
GOLD Site Supporter
I was bored, so while surfing around the web I stumbled across an article on QRP Dummy Loads. Hey...something that I didn't know existed...I think I should build one to rid myself of this boredom. So I looked at a lot of plans, and settled on this one at: http://www.n5ese.com/dummy3.htm

I didn't need the second BNC connector to a voltmeter, so I just put in the resistor packs to come up with 50 Ohms at 8 watts max. My Yaesu FT-817ND only outputs 5 watts max, so the 8 watt capacity is a nice buffer. I have a Swan wattmeter to measure the radio output, and I put the dummy load after that. It worked great on the FT 817 as well as low power output on my FT-450D (went up to 8 watts intermittent). It did a fine job without heating up at all. Overall, the unit is only 3-1/2" long, and is made from 3/4" copper pipe and caps. The plans said it could go into a 1/2" water pipe, but the surplus carbon resistors I got were a little too large to fit as designed. It's still compact enough for me.

For you old timer hams and electronics geeks, keep in mind that this is a big deal for someone with very little electronics background, and virtually no assembly experience. I was patting myself on the back when the damn thing actually worked when I was done.:yum:

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After working off a shitty piece of one-sided copper board, I finally got the solder connections to make so I could get down to the design rating. If I make another one I'll do things differently.

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Took measurements across the bands, and both the R and SWR dropped along with the drop in frequency.

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Now I think I'll make an oil cooled 130W model with an SO238 connector in a 1 qt. paint can filled with mineral oil. Gotta find some cheap 1K Ohm 3W resistors off ebay. My surplus guy wanted $1 each for them, and I can get the 20 pieces I need for $6.20 including the shipping. Sorry surplus guy, but you lose on this one.
 

JEV

Mr. Congeniality
GOLD Site Supporter
So, does this let you boost output without heating things up?
The purpose of the dummy load is for testing the radio's RF output, without sending a carrier across the airwaves. All adjustments to the radio are done while sending the RF signal into the dummy load, and nobody gets pissed off in the process.
 

ki0ho

Active member
GOLD Site Supporter
The purpose of the dummy load is for testing the radio's RF output, without sending a carrier across the airwaves. All adjustments to the radio are done while sending the RF signal into the dummy load, and nobody gets pissed off in the process.


Except maby you ..if ya forget and pick it up...after pushing it a bit to hard!!!!!!!:whistling: lookiny good though!!!!
 

JimVT

Bronze Member
GOLD Site Supporter
my testing on lowest power and sending "test" with my callsign even turns my motion lights on.
 
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