Looking for a 50ohm, 100W resistor....

[Andy1845c]

I am in search of a 50hm: 100W (or higher) power resistor. Anyone know of a source for an odd ball like this? Been googling, but haven't found larger the 22W yet.
It needs to be non inductive.

 

[mneary]

288W resistive heating element?

Or, you could hook up a total of nine of the 22W resistors in series-parallel. (3 in series; then 3 series strings in parallel.)

 

[mneary]

Of course you could also get 300 ohm 22W resistors and hook six of them in parallel. That might be lower profile.

 

[Sceadwian]

Will give you larger surface area for heat dissipation as well.

 

[stevez]

Caddock makes them - see the Digikey site or catalog. Keep in mind that like all ratings, the 100 watts is based on conditions that are well described. You'll need to adjust the power handling capacity down or up based on the conditions you expect.

 

[on1aag]

El cheapo dummy load.

Hi Andy,

You could use a reel of 100 m RG 58 and a 20 watts dummy load.
If you can get your hands on 300 m RG 58 you don't even need a
dummy load any more. If you want it to handle even more power
you can cool it in a water tank.
Don't use the bath-tub unless you are single !

on1aag.

 

[Andy1845c]

Have you seen these in the Digi Key catalog Steve? I just looked again and don't see anthing past about 5 watts thats not wire wound. It is for a RF dummy load.

I found one site that offered carbon power resistors wholesale, I sent them an email, but I'll have to wait and see if they are willing to sell 1 or 2 or can point me to somone who can.

 

[hjames]

Digikey, catalog page 1516: TL88K50R0, 114W

There's a couple other ones that are also in the same ballpark - all are thick-film types.

err, corrected that - the data sheet has the inductance at 50-100nH, so if you're dealing with frequencies in the 10's of MHz, this resistor will start having a couple percent of error. I think I had some of the "power chip" parts made by the same company - they're a continuous sheet of resistive material deposited on ceramic.

 

[Roff]

If you want one badly enough, there seem to be lots of them on Ebay. Search Ebay for "dummy load".

 

[Dean Huster]

OK, Ron. Did you get permission from Tektronix to use their Wizard? Didn't think I'd notice, did you?

Dean

 

[on1aag]

Dummy load.

Hi Andy,

Farnell has some and they come cheap too.

https://uk.farnell.com/jsp/search2/...arch_001&Ntt=resistors&Ntx=&_requestid=183606

https://uk.farnell.com/jsp/search2/...arch_001&Ntt=resistors&Ntx=&_requestid=230626

on1aag.

 

[CheapSlider]

Dummy Load

It appears that you're looking for a dummy load for a transmitter. ("50 ohm, non-inductive").

This would be available from a **broken link removed** that caters for Amateur radio and/or CB

on1aag's idea could work, but stay away from water. Use oil for cooling.

Most resistors that are commonly available (carbon film, metal film, wirewound) are inductive so they can't be used to make up a dummy load for RF.

Ceramic resistor such as MHP100 would be suitable. (You could either request a sample or try a distributor)

edit: corrected spelling of "on1aag"

 

[Hero999]

What frequency are you using?

The chances are that most resistors are too inductive. If it's for anything above about 10MHz you really need an RF dummy load.

 

[stevez]

Andy - I am sure they are in the Digikey catalog and on-line. Caddock is one of the manufacturer's. To get the most out of the resistor it has to be carefully mounted to a proper heat sink. I can tell you that friends have experimented with these - running 100 watts under conditions that exceed the specs - and found that for short periods - 30 seconds or so - the resistor hold up fine.

In one case we discovered that the 100 watt rating was at 25 C. That doesn't allow for a lot of temperature difference - and in most applications would require a derating from 100 watts.

Look again - you'll see them.

 

[on1aag]

Dummy load.

Hi Andy,

I have been doing some digging and I managed to find a couple.
They are marked "RNP20S", I have them in 47 hm: and 50 hm:.
Did some googling too:

**broken link removed**

https://pdf1.alldatasheet.com/datasheet-pdf/view/156600/DBLECTRO/RNP20S.html

**broken link removed**

You can buy them from Barend Hendriksen in the Netherlands,
he has also some flange dummies, but they aren't that cheap.
There are more suitable resistors in his catalogue and you might
find a local distributor when you use the type designations from
his catalogue.

**broken link removed**

on1aag.

 

[Roff]

OK, Ron. Did you get permission from Tektronix to use their Wizard? Didn't think I'd notice, did you?

Dean

I'm surprised it took you this long. I knew that if anyone recognized it, it would be you. I've been using it for several weeks.

I remember it was even in the parts list of the 454 scope. Something like,

W1    Wizard   1 each   nonreplaceable

Ron

 

[Ambient]

here are some from allelectronics. They have a 50ohm 220Watt. Its gonna be BIG though.

https://www.allelectronics.com/matrix/Power_Resistors.html

 

[Roff]

here are some from allelectronics. They have a 50ohm 220Watt. Its gonna be BIG though.

https://www.allelectronics.com/matrix/Power_Resistors.html

Those are wirewound (inductive).

 

[Andy1845c]

Thanks for all the resopnse guys!

I am looking for a replacement resistor for my "cantenna" (long topic about this a while back). I can get knock off of the cantenna with oil for about 70 bucks + shipping, but I want to explore my resistor options before I do that.

It will be used for amateur frequencys.

The resistor will be immersed in mineral oil for cooling.

I will look at Digi Key again when I get home. It would be awsome if they have it.

 

[Andy1845c]

Digikey, catalog page 1516: TL88K50R0, 114W

There's a couple other ones that are also in the same ballpark - all are thick-film types.

Found it, but yikes, expensive.