Great video Randy. I built my 12W Dummy Load with a Schottky 1N5711 Diode RF detector and a six 300 Ohm 2W resistors in parallel. I placed it in yet another Altoids Tin. BNC in front and two 4mm Banana Jacks for connecting the meter in rear. I'll post a pic in the AmateurLogicTV social sites.
This was the first thing I built after I passed my General while I waited for a QRPguys FT8 transceiver kit to arrive. Not sure why but a .01uF mylar capacitor I had on hand did not work for voltage measurements. Switched it out for a ceramic capacitor and it worked fine. Thanks!
I know you made this a while back but it's still relevant and useful today, thank-you. Much better explained and made than similar offerings on RUclips.
Randy, awesome job, a real nice "back to basics" for the new players out there. So many hams just want to buy a signal and have no real understanding on how things works, thanks for showing that it does not cost a lot nor take an engineering degree to do simple experiments. Keep up the good work. 73 KK4EDE
I hate to be a party pooper, Randy, but metal film resistors are also rather inductive. For best results, use carbon composition types (or non-inductive resistors specifically designed for RF use). Dave - W7SN
Ahh, very good. I know with the QRP kits you can get from China, they come with a single 1 or even half watt 50 ohm resistor as a dummy load. I've built kits that almost smoke them. Very interesting little project, especially gauging power output, good stuff.
Good project! I am going to build one. I have a question about the formula to calculate watts. I would have though the voltage should be multiplied by .707 to convert to RMS voltage before squaring. Seems like I am missing something. Can you please explain when you would/would not convert to RMS.
Great video. I built something similar many years ago without the diode and capacitor, and it seemed to work well. I wonder how difficult it would be to wire up some gauges to have a direct reading instead of having to use a voltmeter?
Randy, the cap and diode are for power test only correct? You can have the dummy load with the resisters only is that correct? I heard no mention of this... thanks w7wza
Is that the old Fluke 8060 Randy?? I am more in need of a (better) 3KW dummy load. I have a lovely 1KW, and a DIY Aryton Perry wound resistors in an oil bath that handles ?KW. 5ish KW intermittent. I have audio loads @ 1,2,3.2,4,6.6,8,12,16,32, & 600 Ohms @ 200Watts-1.5KW, with speaker emulators, but those emulators are exactly like a tuned tank circuit with RF. My QRP 50 Ohm is a thick film precision resistor on an old CPU heat sink. That gets me up into GHz. It works. The metal film is actually spiral cut on a porcelain rod, so you are limited to about that 225MHz. I bought 7,000 what I thought were carbon comps, but they are actually wire wound, so no RF loads with those.
Why doesn't anyone use surface mountable resistors like www.rfparts.com/dummy-loads/dummyloads-surface/a3rrc4.html. Seems like you can just bolt it to big heatsink and call it a day.
Nicely done project - very useful Randy.I have a special appreciation for your terrific engineering practices. Doing the math confirms everything.73 Brian w6dwy
Does anyone know anything about the GigaParts DX-80? here is a link to it.www.gigaparts.com/radiowavz-dx80.html?gclid=CK-A1MiVtdMCFUKSfgodSa4Ltg I ordered one hope its a good antenna?? JK
Great video Randy. I built my 12W Dummy Load with a Schottky 1N5711 Diode RF detector and a six 300 Ohm 2W resistors in parallel. I placed it in yet another Altoids Tin. BNC in front and two 4mm Banana Jacks for connecting the meter in rear. I'll post a pic in the AmateurLogicTV social sites.
Sound good
This was the first thing I built after I passed my General while I waited for a QRPguys FT8 transceiver kit to arrive. Not sure why but a .01uF mylar capacitor I had on hand did not work for voltage measurements. Switched it out for a ceramic capacitor and it worked fine. Thanks!
I know you made this a while back but it's still relevant and useful today, thank-you. Much better explained and made than similar offerings on RUclips.
Simple
Randy, awesome job, a real nice "back to basics" for the new players out there. So many hams just want to buy a signal and have no real understanding on how things works, thanks for showing that it does not cost a lot nor take an engineering degree to do simple experiments. Keep up the good work. 73 KK4EDE
Thanks
This was really useful, and nicely paced. Really appreciated.
I hate to be a party pooper, Randy, but metal film resistors are also rather inductive. For best results, use carbon composition types (or non-inductive resistors specifically designed for RF use). Dave - W7SN
Thanks for the tip
Thanks for all your hard work and time Randy...Lee/NN7X
Very nice. Great piece of test equipment. Thanx for showing me how to homebrew this.
Ahh, very good. I know with the QRP kits you can get from China, they come with a single 1 or even half watt 50 ohm resistor as a dummy load. I've built kits that almost smoke them. Very interesting little project, especially gauging power output, good stuff.
Outstanding project.
I'll do you one better than a thumbs up, shared this nice project as well.
73 Julian
Me too. On the 470 repeater group for East TN and our QRP group on FB.
thanks
This is great just what I was looking for .
This is awesome, Randy. I've been wanting to build one of these for my radio. Thanks!
Warm up your iron
Hehe...I actually ordered the necessary parts last night right after watching the video.
that was quick
Another great project Randy for the QRPer's kit and test bench =) GREAT JOB =)
All QRPers need one.
I have been thinking of raiding my parts box an starting one .... I probably have everything I need in there =)
Thanks for your nice videos. Always nice to watch
Good project! I am going to build one. I have a question about the formula to calculate watts. I would have though the voltage should be multiplied by .707 to convert to RMS voltage before squaring. Seems like I am missing something. Can you please explain when you would/would not convert to RMS.
Nevermind. I found a post that explained how the rms conversion constant drops out of the equation.
Great video. I built something similar many years ago without the diode and capacitor, and it seemed to work well. I wonder how difficult it would be to wire up some gauges to have a direct reading instead of having to use a voltmeter?
Easy with an Arduino. It can do the math and then output to a display. I'll probably do a video on that in the future.
Randy, the cap and diode are for power test only correct? You can have the dummy load with the resisters only is that correct? I heard no mention of this... thanks w7wza
You don't need the cap and diode. They are only used to supply a DC voltage to a meter for measurement.
What would I have to change to get 50 ohms and 30W capacity on this project?
Awesome video, as always, Randy. Thanks. Did I miss the details of your spreadsheet? I liked your soldering lesson. "Not pretty, but aaah it'll work."
I didn't show it. Just add the measured voltage + the .25V for the diode, square that and divide by 25 ohms.
Is that the old Fluke 8060 Randy?? I am more in need of a (better) 3KW dummy load. I have a lovely 1KW, and a DIY Aryton Perry wound resistors in an oil bath that handles ?KW. 5ish KW intermittent. I have audio loads @ 1,2,3.2,4,6.6,8,12,16,32, & 600 Ohms @ 200Watts-1.5KW, with speaker emulators, but those emulators are exactly like a tuned tank circuit with RF. My QRP 50 Ohm is a thick film precision resistor on an old CPU heat sink. That gets me up into GHz. It works. The metal film is actually spiral cut on a porcelain rod, so you are limited to about that 225MHz. I bought 7,000 what I thought were carbon comps, but they are actually wire wound, so no RF loads with those.
8024B. Thanks
great project
Thans for the video. I bout a few 1N914 SMALL SIGNAL DIODES 200mA 100V. Do you think I can use these instead of the 1n5711? Thanks for your advice! 73
Give it a try. It may not be as sensitive with low power.
Thanks Randy!!
Randy I want to build a 100 watt dummy load... would it be only increasing resistors to say 20- 5 Watt, 1K resistors?
Without doing the math, that sounds good. Keep the leads short.
Thanks Randy, and I really enjoy your videos ...73 KD9GRP @@K7AGE
so, is that easy to measure the power? Is it valid for a 433mHz and 2.4gHz? Grat for a simple arduino project with a lcd or oled
I tested it at 144 Mhz, results were very poor. It would be even worst at 433 and higher. I would not recommend using this beyond 28 MHz.
Why doesn't anyone use surface mountable resistors like www.rfparts.com/dummy-loads/dummyloads-surface/a3rrc4.html. Seems like you can just bolt it to big heatsink and call it a day.
Am I going to see this on HN?
Tonight, the short version
Error
Nicely done project - very useful Randy.I have a special appreciation for your terrific engineering practices. Doing the math confirms everything.73 Brian w6dwy
Does anyone know anything about the GigaParts DX-80? here is a link to it.www.gigaparts.com/radiowavz-dx80.html?gclid=CK-A1MiVtdMCFUKSfgodSa4Ltg I ordered one hope its a good antenna?? JK
I don't know anything about this antenna. Mixed reviews on eHam www.eham.net/reviews/detail/6092