2.25 kW Power-Dummyload with Heat-Spreader and Water Cooling

this dummyload is used for developing and testing high power LDMOS RF-amps. It handles ober 2kW power up to the 6m band. It is very small because it uses water cooling (only 200x120x10mm).
www.dj0abr.de

[@stephenbamford]

A very impressive display of some great engineering and lots of great 'know how'. Thanks for sharing.

[@anandarochisha]

Very nice Precision work. Bravo.

[@user-qo5do8fi9o]

Thank you very much for this serie of video! You've done the great work!

[@deinprinz1]

Great project and super explained

[@williammiller5490]

This is an awesome design and tails nicely with the amp as well. Thanks so much for your efforts. I can't wait to get started on mine for my KX3 foot warmers. Thanks again. Bill / WB9FFG

[@ng7m-ham-shack]

Excellent Video and Engineering! Amateur Radio at it's finest, building and engineering your own gear. 73 de Max NG7M

[@ElektronikLabor]

Eine sehr schöne Last! Gute Idee, die Widerstände gebraucht zu bestellen!

[@k5azebud988]

Very nice project, well done...

[@-costas-balasoppulos5840]

Nice job sir. Balasopoulos Kostas Greece

[@fnordist]

Gute Arbeit Scotty!

[@ernstvielsmaier9052]

nice video, thank you for the good work

[@daleburrell6273]

VERY NICELY DONE- AND YOUR ENGLISH IS QUITE GOOD!!

[@ComandoRebelles]

Very good project , I learned a lot. Thanks for show us. 73.

[@wisehomo]

hhh I think you love your water cooling invention you keep good work. I love your work.

[@northbetrue]

Brilliant!

[@user-qo5do8fi9o]

1) copper and aluminium is not the best pair, especially with water nearby. 2) what about the drops of solder inside the channels: it will make resistance to water flow. 3) I'd also recommend making additional fixture to the resistors with screws and bars, just in case, so if anything goes wrong, the resistors would not dropped out, but internal resistors structure will anyway be melted, so now I think, no need to do it.

[@cryscrystiii7023]

👍 Best jobs! I would have connected in cross the resistors to a minimum inductance and plug would come in the center of the radiator.

[@ghlscitel6714]

Nicht schlecht, Herr Specht!

[@kevinkang4308]

Very nice dummy load. Can I have a look at the water pump and bottles?

[@user-ww6pb7rj5s]

recommended feed Power is 2250w for ssb mode only but fm /cw mode is half power reduce , because resistor temp over then 150 degree ( resistor failue)

[@michaelnobibux2886]

These resistors usually have limited voltage ratings , so the amp must be very well matched to 50 ohms! Also dissimilar metals in the presence of cooling water is a recipe for corrosion! Take care!!

[@ne2i]

The water is in the copper side. The aluminum does not touch the water. Its just a cover plate

[@RC-Heli835]

This is very nice! Why could you not place a gasket in between the soldered plates and screw them together instead for easy maintenance? Car water pumps do it every day for years and years they work.

[@og2xradio898]

Nice

[@sbreheny]

Did you clean out the flux from the cooling channels after soldering?

[@guoss7741]

Connecting 9 resistors like this will affect the inductance or not.

[@zeljkoadzic1692]

is this really 750 W continuous load?

[@doug8085]

So, no radiator in water circuit? Think something like a computer water system would be much help here.

[@JamesJohnson-ny3xz]

VERY COOL, 😁.

[@brucetraudt1571]

you selling these??

[@sudriyodriyo8557]

Resistor 2 kaki belinya dimana??

[@muckemark4318]

woher bekommt man so einen guten wiederstand für sowas selber zu bauen? und wievil braucht man dazu? wäre super wenn man das erfahren könnte.

[@hamshallofshame9890]

Entweder Du hast das Video nicht wirklich angeguckt oder Dein Englisch ist so schlecht wie mein Mandarin.

[@richardnanis]

How do you solder these resitors on this massive block of copper??? You need a few kW soldering iron or gas burner for that. Ahh - i see the kitchen stove did the work :-)

[@harry4516]

right, hi. Most important is to give a few bucks to your wife for shopping. If she left home, you go into the kitchen and heat up the copper block until the solder melts. This is a critical temperature because the ceramic case of the resistors will start floating when the solder is melted and therefore must not be touched.

[@MrRichard57000]

so if i use one resistor it s should handel 200-250 watts for a minute??(for 11 meter band)cool video btw.....

[@harry4516]

yes, it handles 200 watts for long time. The water cooling is very effective. But the resistor must be "soldered" to the copper.

[@MrRichard57000]

yes oke,i orderd 4 resistors (with one connector) and want too use 2 rows parralel and then connect them in serie(of course with some kind of insulation?)..in this case can we handel one kilo watt??thanks for your feed back!!!

[@harry4516]

Resistors with one connector are a problem because you need insulation. Better to use resistors with two connectors and solder it directly on the copper plate. In my first version I tried it with insulation, but the resistor burned. You get 50 ohms / 250 watts resistors with two connectors easily from aliexpress for low price. You can also use two resistors with two connectors and two resistors with one connector, which gives you a very good ground connection.

[@MrRichard57000]

yes oke,i saw those with the double connection...believe it ore not but shippmant too the Netherlands was 60 euro and too Germany 1,74 euro....i m going to make a smale one with one resistor(only for 200 watts and a few seconds).and will order those with the double connection and let them ship too my german collega....thanks for the info harry...

It is very nice project! Ha7nk

[@rogeronslow1498]

Those resistors are not designeg to be soldered to a heatsink. You may damage them.

[@harry4516]

yes you are right, its a big risk. If they get touched during soldering they are damaged. But if we are very careful the cooling is very nice.

[@andrephilipp23]

very COOL ;- ) 73 de OE8ASR

[@robmccance]

Harry - you sure like the water cooling!! Nice work. Here's a similar air-cooled dummy load I made back in June: www.qrz.com/db/N4GA Bottom of the page. Take a look! Rob

[@harry4516]

Rob, your dummyload looks really cool, but what ??? I see 25 resistors, 250 watts each. 25 * 250 = 6250 woww :-)

[@hickenc2187]

자세히는 못 봤는데 ㅎ 내부에 물과 반응하지 않는 코팅을 했나? 안 했나? 예를 들어서, 수산화알루미늄은 잘 자랍니다.. 금속은 다 그러함. 수냉방식 펠티에냉장고 만들어 보니 그렇더라구요. 가공하실 분 참고를 하소서. 그리고 원터치피팅은 기체용도임 그 구조와 리테이너의 재질상 액체용도로 쓰면 단명함. +덕분에 공정 잘 보았고 대단히 고맙습니다.

[@hickenc2187]

I didn't look closely, but is there a coating on the inside that doesn't react with water? didn't you? For example, aluminum hydroxide grows well. All metals do. It was like that when I made a water-cooled Peltier refrigerator. Please refer to the person who is processing. And one-touch fittings are for gas use. Due to their structure and retainer material, they are short-lived when used for liquid applications. +Thank you, I saw the film and thank you very much~~~ !!!!

[@LB3HC]

Harry, where can I find your e-mail address?