Re: Dummy load and wattmeter


Look forward to seeing that, I need one!


Colin – M5FRA


From: <> On Behalf Of jjpurdum via Groups.Io
Sent: 19 June 2018 15:04
Subject: [QRPLabs] Dummy load and wattmeter


Hi Steve:


Al (AC8GY) and I had our Builders' Group build an old fashioned dummy load, but with a power meter, too, as seen here:



We tested it for 5 minutes @ 200W and while the mineral oil got pretty toasty, no damage to the parts. The nice thing is you don't need to tether it to a PC and the meter unit unplugs easily from the DL. It costs about $20 to make and uses a Nano to drive the meter. The meter is one of those 0.96" OLED's. No PCB is needed; just a small piece of perf board because it's so simple. There's a builder's manual for the project, too. If you calibrate it with a know power source, it's reasonably accurate. It will be coming out in the Nov. QST.


Jack, W8TEE


On Tuesday, June 19, 2018, 9:24:24 AM EDT, Steve Nichols via Groups.Io <infotechcomms@...> wrote:



Well done Colin,

It might be worth playing with spacing out/compressing the turns on the filter toroids as you may be able to increase the power slightly.
But, having said that, my MFJ ATU power meter, on the 30W setting is woefully inaccurate at QRP levels.

I have been fiddling with my QCX again and replaced the three BS170s in the PA section. That's the third set now - first set I thought I had blown, second set came from China and only gave 1.8W, third set came from GQRP club and now give 2.7W with a 12.6V lithium battery. I'll stop there on the grounds that "if it ain't broke don't fix it"!

I have the Sandford QRP Power meter which is a handy tool to build and own.

Steve G0KYA


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