Building a Simple & Cheap 50-Ohm Dummy Load.

[@AGeekNamedRoss]

Thermal grease is easy to find where you buy computer components (processors, GPUs, etc). Be careful that you don't get one w/ gallium in it, or it'll react with your aluminum box and will be electrically conductive.

[@darrenbird2526]

Great video, thankyou for taking the time!

[@thomasr.jackson2940]

Yeah, projects like these are good and helpful.

[@jbx907]

that wire will cause an inductor in series, you should have the terminal right on the connector

[@kchoudri]

Thank you for sharing,,, I have been looking to build one myself but didn't know where to start... this video is a great help. I will start sourcing the components and build my own dummy load. There are two main factors I want to build this project, its a good practice with electronics,, and it will be much cheaper compared to the ready made ones.

[@RadioPrepper]

Excellent!

[@mariosergiosamora5189]

My friend good morning. Congratulations on the project. I did an equal dummy load. Perfect operation. It is even better by placing a heat sink to use an approximate power of 100W. Thank you and congratulations again.

[@jackK5FIT]

Great project! Thanks.

[@mickstermouseter7059]

Excellent video!

[@adrongarretson6195]

Yes I love it when you build simple projects like that and super cool I even take screenshot to your schematics and then copy it down and use it for a later date thank you very much by the way

[@RadioPrepper]

Great thanks. I will publish more...

[@uncledelvid6204]

Wow !! I'm gonna try it myself. THANK YOU !!!! 🤓😊

[@andrewrudlang2785]

Excellent, thank you so much, saved me a lot of money! I have a large aluminum heatsink from an old desktop processor I can use, way overkill but fun!

[@KCnoSurrender]

Subbed off the logo!

[@OH8STN]

Hello buddy. I have forgotten to comment on this video earlier. The answer to your question at the end of the video is absolutely! We love these types of videos, and you're the master of them. Please do more :-) I'll put this one up on the website. Thanks for sharing.

[@RadioPrepper]

Thanks! I have been under the radar lately, bad cold, but back in business now :-)

[@MyTube4Utoo]

All my radios combined wouldn't put out (250) watts. *lol* Cool little project. QRP Labs has a 50-ohm, 20 watt dummy load kit for $8.50. Hans designs some of the best kits around, and everything is always priced very reasonably.

[@RadioPrepper]

Mines neither! Yep, impatiently waiting for the QSX.

[@MyTube4Utoo]

@@RadioPrepper I hear ya! I'm on the 'QRP Labs' newsletter mailing list, but I still check the website often, just hoping to be surprised. I ordered an HB-1B to keep me preoccupied. *lol* I ordered it on (11-2-2019), and it's still not here. They said they had to build and test it. I guess they must have shipped it from China by carrier pigeon, too. ;-)

[@a2phil]

@@MyTube4Utoo From my experience, just about ANYTHING shipped from China takes AT LEAST a month, but just about ANYWHERE else, a week or two...

[@sandraabarca6029]

@@RadioPrepper hello may when Hans releases the QSX you could interview him. that would be appreciated.7 3

[@Aussat]

Thanks Gil, this is great and so good I have ordered the parts from Ebay! Excellent about time I start to get back into building!

[@RadioPrepper]

Excellent!

[@VK2AAK]

A good, simple project ... thank you! ... BUT, while those resistors might be rated for 150 Watts they will fail well below that unless a LOT more heat sinking and/or cooling is added. I reckon that little die cast box would struggle to dissipate much more than 10 Watts for a few minutes. Also, those resistors are designed for stripline connections and using hookup wire between the input socket and the resistor will limit the usefulness of the load to HF frequencies. I reckon it would be marginal at best at 50 MHz and probably quite poor above that.

[@georgeewing21139]

Do you work for MFJ ??

[@VK2AAK]

@@georgeewing21139 No, I’m retired and live in Australia … and there’s no MFJ manufacturing here.

[@robinbrown7019]

Great job

[@johnmarchant9253]

Great idea, many thanks.

[@RC-Heli835]

I like the box man! Thanks for sharing!

[@daveschwarz5279]

You couldl used baby oil ( pure mineral oil ) in the box to help to dissipate the heat at higher wattages

[@RadioPrepper]

Indeed thanks.

[@roykilo9642]

reading my mind

[@glenmartin2437]

Thank you.

[@furonwarrior]

I heard mineral oil should help give you more watts to test with and to keep the temperature lower.

[@RadioPrepper]

I never use more Watts ;-)

[@robertlundstrom8061]

Just saw this today. Very nice project indeed. Please think up some more.

[@imhidingintheshop8889]

this is good stuff! thank you.

[@hhampton]

Love these types of projects. Please keep them coming.

[@RadioPrepper]

Will do!

[@hectorpascal]

Take care with the resistor tab when soldering! They are very easy to rip off by accident :( (and then it is VERY difficult to solder to the remaining tiny strip.)

[@RadioPrepper]

Indeed, I almost did!

[@josephcooksley3219]

Cool construction yes how ever i would have thought some paste on lid seal surface would be beneficial ???

[@RadioPrepper]

Probably..

[@chrismayer7762]

Great project

[@joellewis4806]

The box itself is a hell of a heat sink

[@2e0mpg]

Great content thank you

[@stevejones8665]

Now you have shown every radio enthusiast how to make a cheap as chips Dummy load I wonder how many will pay an extortionate amount for one with a name on it that's probably not even as good as yours Gil.👍👍👍

[@RadioPrepper]

So much other radio stuff to buy... Always nice to save a bit for the next transceiver!

[@frankjoh1015]

Thank you. Just ordered the parts on ebay. Now to find some thermal grease..

[@RadioPrepper]

Don't put that stuff on your skin!

[@frankjoh1015]

@@RadioPrepper Is it like anti-seize? Turns everything silver.

[@RadioPrepper]

No, different compound.

[@ke0ourwilliam982]

Like a lot. Keep doing them.

[@HNXMedia]

Love this!

[@jamescopeland5358]

I think that's a great project

[@leos9865]

Thank's

[@DanTaylorDotCom]

A nice little and useful project for me. Thank you.

[@RadioPrepper]

Great!

[@azarellediaz4892]

Great show. I would like to understand, what are the purposes of the diode and the capacitor, I have never seen a dummy load with these components.

[@RadioPrepper]

I did not use a diode or capacitor.

[@josephhager1933]

Great video love these projects especially for homebrew Qrp

[@stevel.4461]

Perfect!!

[@doughenry8137]

Merci Gil, j'aime vos presentations.

[@RadioPrepper]

Merci!

[@skovdesurvival4022]

So signal to the resistor, then "ground" to chassie and also "SMB" body? :)

[@RadioPrepper]

Yes. I don't remember what I did though ;-)

[@perfectomprg]

just pointing out the elephant in the room here: there's something hanging out of your nose

[@RadioPrepper]

Food reserves for later..

[@KE0ZMK]

Thank you for the video! I have built this project but with the only difference being I used a 100w resistor. As far as the "rf probe" function goes, I am getting a reading with a multimeter set to DC but it seems to be about 27% off (to high) with the calculation you hold up on the paper. Am I missing something?

[@KE0ZMK]

Revision, I now see it depends on the frequency. I was using two vhf radios in my prior tests that I mentioned and now I tried UHF and its 800% higher. I'm thinking HF should be pretty close but I will try that another time. Thanks again for the project!

[@RadioPrepper]

It's probably a wound resistor, which makes a coil in AC. You must use a carbon resistor, or other, but not wound..

[@KE0ZMK]

@@RadioPrepper It looks exactly like yours just 100w instead of 250w but I did get them cheap on the internet.

[@RadioPrepper]

Weird, I only used mine on HF though, so who knows...

[@md10591]

very nice little project ! great for beginner and inexpensive . 73 , ka2kug

[@davidsradioroom9678]

I had to make a simple dummy load to test a cable. I had a spare SO-239 connector and I had a stack of 100 ohm resistors. I put two of them in parallel for 50 ohms, and connected the pair to the SO-239. Found out the cable under test was bad. Other good cables tested good with my antanalyzer throughout the spectrum.

[@stewartrv]

Very nice I like this approach. You don't mention if this is a carbon resistor or not - but it is important to use a carbon resister as wire-wound versions have a lot of inductance and that's not good...

[@RadioPrepper]

It is.

[@Spasmomen]

I really love these videos. You make me want to get a license.

[@RadioPrepper]

Go for it!

[@mariofilipe2289]

Go, go, go. You are welcome. 73

[@sarto7bellys]

Thanks for posting this, off the back of your post I made a 150W 50ohm dummy load just like you did and using a Surecom power and swr meter it works great and shows an swr of 1:1, I then built a second dummy load using a 20W 50ohm resistor this shows a swr of 19:1, my question is should I be worried about the swr or not when using a dummy load, I have googled this and can't seem to find an answer, I just wondered what your thoughts are ? 73's

[@RadioPrepper]

Yes. You might have used a wire-wound resistor, which if it shows 50 Ohms using DC is an inductance using RF AC. Do not use It!

[@sarto7bellys]

@@RadioPrepper Thank you for coming back, I will bin it

[@xszl]

So, nobody is gonna say anything about the thing in his nose ? Ok. I like the projects, yes.

[@Debraj1978]

Elephant in the room.

[@bobfrediii2131]

he put a booger warning at the start

[@RadioPrepper]

I ate it.

[@MrDatbeme]

Just getting back active after a long break. Thanks for this project and your other great videos. 73 de wd2t

[@RadioPrepper]

Welcome back!

[@DonDegidio]

Hi Gil, Nice build. The RF Probe circuit is what I like about my Heath Cantenna as it has that on the top of the can. 73 WB3BJU

[@RadioPrepper]

Too bad I was missing one resistor!

[@xtibi1]

Onto many dummy loads it is written 3GHz. Are good for testing power in 136-500 MHz range ? (radios within VHF and UHF bands)

[@RadioPrepper]

I would say yes. When you get into GHzs anything becomes an antenna and affects measurements, but then the bandwidth is so wide... Things get really weird above UHF...

[@majorkonfuzion1007]

can i harvest a similar resistor from common electronic appliances ?

[@RadioPrepper]

I doubt it.

[@RodneyStevens]

What is the attenuation at the probe point?

[@RadioPrepper]

Hi, no idea. It works...

[@muppetpaster]

So sad you did not show the finished inside.....Missed opportunity.

[@RadioPrepper]

Darn yes...

[@k2cjbradio]

Great little project! Now I have to look on ebay for the resistor! 73 de K2CJB

[@1crazynordlander]

You found one and built it! I enjoyed both videos!

[@k2cjbradio]

1crazynordlander Yep!! This is the one I mentioned in my video! :-)

[@fredcooper5236]

K2CJB. Plenty online for a couple of dollars. 👍 Google 250n50.

[@jamesw6529]

Would be so kind as to make a parts list with links?

[@RadioPrepper]

Sorry, no time. I got everything from Ebay.

[@joemason9187]

Fantastic I've just built 10w one but this is way better great vid

[@therfnoob7697]

Hello Gil, great channel! I just started mine also inspired by yours :) One question: who is it called in french (if you can recall) the "locktight" glue you used to fix properly the BNC connectors? I live in france so if you can tell me the exact name, I'd probably be able to buy the same for my projects :) Keep up the great work!

[@RadioPrepper]

I have no idea, LOL, I can't find the bottle! I always called it Locktight, but of course that is a brand name...

[@therfnoob7697]

@@RadioPrepper thanks radioprepper!

[@fredcooper5236]

Loctite Blue 242

[@RadioPrepper]

Mine is SADER Colle speciale experts, blockage vis écrous.

[@jacobdavis000]

I'd be interested in seeing an SWR or S11 measurement on it to see how flat it turned out to be.

[@RadioPrepper]

I will post it on radiopreppers.com tonight...

[@JT-py9lv]

What would be the result if you soldered 3 or 4 of these together ? and maybe used an old computer heat sink ? to attach them to ?

[@RadioPrepper]

You'd need a bigger heat sink than that... Also 3 would not work. You'd need four. Pair them in series then connect the pairs in parallel for 50 Ohms.

[@PBenetton]

Can I calculate output power using a simple swr meter with field meter? I can measure voltage with a multimeter if needed. It's an Olson CB-067 swr meter. The manual says that you can use it to calculate power, but it doesn't give any equations or methods. Thanks

[@RadioPrepper]

See my video on building a dummy load. You need a diode and a capacitor...

[@PBenetton]

@@RadioPrepper but I wonder if I can do it with the gear I already have, the Olson with an fs meter. It says I can determine wattage by reading the %ref power and some calculations. Any thoughts on that? And, BTW, the formula is pwr=(V*0.25)^2/50? Where does the 0.25 comes from?

[@RadioPrepper]

That I don't recall...

[@goatmoag]

Sweet

[@banjobill10]

why is thermal grease needed?

[@RadioPrepper]

For better thermal conduction to the case, though for QRP, most likely not needed.

[@robsartori9365]

Going to have a go at this, what gauge of wire did you use to make the connection from the bnc connection to the resistor ?

[@RadioPrepper]

Hi, no idea!

[@yogyosakti1031]

Good job ... I was make it, but finaly , I measure < 59 ohm ..., why ?

[@RadioPrepper]

Probably the resistance of the box, but 59 is good enough!

[@elpechos]

Have you tested the SWR of this? The power resistors I've tried from ebay have so much inductance they get bad SWRs and make terrible dummy loads.

[@RadioPrepper]

I can't remember exactly but it was low..

[@elpechos]

@@RadioPrepper Thanks, maybe I got a dud. I was worried ebay might be selling all fakes

[@RadioPrepper]

Does it look the same? Is it a wire-wound resistor? That would not work...

[@sabridges]

I made one of these and it works great. I used a 100w 50ohm resistor that measured 50.6 ohms. It's more than up to the task for my radios. Thanks for posting the video. N0SAB, Port-de-Paix, Haiti

[@winterburan]

Génial, ça tombe juste sur le fait que j’ai un appareil militaire UHF des années 80, avec un module de sortie de 50W grillé parceque quelqu'un le jouait sans antenne ni charge fictive avant de me le vendre !!!

[@RadioPrepper]

C'est rare qu'ils grillent... Quel model?

[@winterburan]

@@RadioPrepper désolé le retard, le modèle est drumgrange DX 502, je pensais que vous pouviez l'utiliser sur d'autres bandes VHF et UHF à la place il est bloqué par un code de mot de passe, au lieu où je ne peux rien transmettre sort, l'ouvrir a un module TX de puissance à large bande et après lui un module de filtre qui sépare les bandes VHF / UHF, je n'ai aucune idée si c'est le module TX ou le module de filtre qui est endommagé, dans tous les navires sans code de déverrouillage il est inutilisable sur d'autres bandes, je ne peux entrer la même fréquence via le clavier où il reçoit et transmet varie de la bande aéronautique à la bande satellite UHF mais dans la bande 144/430 il ne permet pas d'insérer la fréquence pour le code bloc. ils l'ont certainement mis sans antenne n'ayant pas les connaissances de base sur les appareils TX / RX, je l'ai cherché et je l'ai trouvé ma faute! Ciao

[@jimguelde4068]

Whenever my wife drives, she refers to me as the dummy load.

[@RC-Heli835]

That's totally disrespectful. 😁 😆 😅 😂 🤣

[@Arkferret]

will this work as a dummy load for CB radios?

[@RadioPrepper]

Yes, up to 50W maybe.

[@Arkferret]

@@RadioPrepper i'd be nowhere near the 50 watt limit then.

[@Arkferret]

@@RadioPrepper recieved mine this morning mounted it to a old computer CPU cooler an put all inside a sealed metal tin with just the connector poking out through a hole drilled into it. has to be the flattest SWR reading i have ever seen.

[@chuckk5358]

Great little project. What else ya got?

[@RadioPrepper]

Lots of projects coming :-)

[@naldrus6418]

No heat sink???

[@RadioPrepper]

No. The case does it. I only use it with low power.

[@mrgajeep]

Such a good idea! Thank you for sharing. de Carl (WB0RSZ)

[@Sam-K]

I think it's best to buy a pair or two of 100W halogen headlight bulbs, in case you're working with 12 volts. Extremely cheap and will work right out of the box. Also MUCH safer to use than resistors, which like to blow-up! Interesting project though!

[@VK2AAK]

Great for DC but as those halogen bulbs present nothing even close to a 50 Ohm matched load I wouldn't want to be running my transmitter into them. Stick an SWR meter between your rig and your light bulbs and I suspect you'll rethink the strategy :)

[@jeromegrzelak8236]

A GREAT SIMPLE CLUB PROJECT TNX KG6MN

[@georgecomninos9126]

Big booger!!

[@mrtechie6810]

I cringed when you drilled next to your hand, instead of using a vice! Safety first!

[@nelwandachry8762]

wow

[@ae1tpa92gwtom2]

Who can possibly give a thumbs down here amazing I see 2. Keep up the great videos Gil AE1TP A92GW 73s

[@RadioPrepper]

Thanks.

[@markhenry1144]

Aahh mate, you've got a bat in the cave.....

[@RadioPrepper]

Is that an Australian expression?

[@ThePugMonkey]

Yes mate. Excellent video by the way...

[@michaelf.4535]

There's a booger in your nose! Very distracting!!!

[@bigpimp347]

not sure why he put the resister on the side and not on the flat of the back in the middle.. but at least he's right, more power, bigger heat sink...

[@RadioPrepper]

Shorter wire...

[@bigpimp347]

@@RadioPrepper not really, back of the box nearer the BNC socket, even shorter wire, if you used a big heatsink and an SO-239 socket the holes line up the same as the resistor and you cna solder the resistor direct to the SO-239 with the heatsink sandwiched in between.