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Dummy Load Resistor

 

I'm wondering if a Planar resistor can be used for an RF dummy load. I have a couple 1KW 100 ohm Planar resistors and an 18# heat sink, I can't find my answer anywhere. Any information will be greatly appreciated.
 

John,

Does the datasheet for that "planar resistor" say it's non-inductive?? If not, then it probably won't work as a dummy load, except at audio.

ebay has some 50 ohm non-inductive resistors?but they're not good for much more than 100 watts and most are 50 ohms.? For higher power values, you'll need to search the surplus channels.? Just how big a dummy load do you need, anyway?

73
Jim N6OTQ


On Thu, Sep 28, 2023 at 9:13?PM N0EE via <n0ee=[email protected]> wrote:
I'm wondering if a Planar resistor can be used for an RF dummy load. I have a couple 1KW 100 ohm Planar resistors and an 18# heat sink, I can't find my answer anywhere. Any information will be greatly appreciated.

 

You can always take two of the 50 ohm resistors in series,
paralleled with another two 50 ohm resistors in series.
Should give you 400 watts of dissipation.

I'm using 2 paralleled strings of 4-100 ohm resistors
to get 200 ohms capable of dropping the 8 watts
to slow a fan down cooling my stereo. (120VAC)

They are 1 watt resistors I had in my junque box.

On 2023-09-28 22:23, Jim Strohm wrote:
ebay has some 50 ohm non-inductive resistors?but they're not good for much more than 100 watts and most are 50 ohms.? For higher power values, you'll need to search the surplus channels.? Just how big a dummy load do you need, anyway?
 

Reminds me, I built a dummy load with twenty half watt
1000 ohm resistors in parallel between two coax braids
dunked in a gallon of ND30 motor oil in a one gallon pain can.

I haven't killed it yet using up to one minute tests with 100+ watts.

On 2023-09-28 22:43, Scott, KB3JQQ via groups.io wrote:
You can always take two of the 50 ohm resistors in series,
paralleled with another two 50 ohm resistors in series.
Should give you 400 watts of dissipation.
 

Mite want to check the SWR of it or a scan with a VNA or some such to see how it looks.

A

On 9/28/2023 9:43 PM, Scott, KB3JQQ via groups.io wrote:
You can always take two of the 50 ohm resistors in series,
paralleled with another two 50 ohm resistors in series.
Should give you 400 watts of dissipation.

I'm using 2 paralleled strings of 4-100 ohm resistors
to get 200 ohms capable of dropping the 8 watts
to slow a fan down cooling my stereo. (120VAC)

They are 1 watt resistors I had in my junque box.

On 2023-09-28 22:23, Jim Strohm wrote:
ebay has some 50 ohm non-inductive resistors?but they're not good for much more than 100 watts and most are 50 ohms.? For higher power values, you'll need to search the surplus channels.? Just how big a dummy load do you need, anyway?



--
"Where the Old Soo crossed the New Soo"
Duplainville, Wisconsin

Web page: Http:/www.dupyrail.com

Youtube Channel:

 

Scott,

I may be reading too much into this, but when people post to a group named "ham-amplifiers" and mention "a couple 1KW ... resistors" I can only assume that they plan to homebrew an HF dummy load.

They'd be much better off to buy a surplus dummy load in the 5 kW range that's good to at least 6 meters, preferably higher.? There may be some FM broadcast surplus kicking around ...? I know a guy who knows some guys.? Whatever.

73
Jim N6OTQ


On Thu, Sep 28, 2023 at 9:43?PM Scott, KB3JQQ via <kb3jqq=[email protected]> wrote:
You can always take two of the 50 ohm resistors in series,
paralleled with another two 50 ohm resistors in series.
Should give you 400 watts of dissipation.

I'm using 2 paralleled strings of 4-100 ohm resistors
to get 200 ohms capable of dropping the 8 watts
to slow a fan down cooling my stereo. (120VAC)

They are 1 watt resistors I had in my junque box.

On 2023-09-28 22:23, Jim Strohm wrote:
> ebay has some 50 ohm non-inductive resistors?but they're not good for
> much more than 100 watts and most are 50 ohms.? For higher power
> values, you'll need to search the surplus channels.? Just how big a
> dummy load do you need, anyway?
>
 

¿ªÔÆÌåÓý

Hi ¨C

?

I would say giver it a try. Put it together and then use a network or antenna analyzer and check the DL for return loss. 73 ¨C Mike

?

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

848-245-9115

?

From: [email protected] <[email protected]> On Behalf Of N0EE via groups.io
Sent: Thursday, September 28, 2023 10:14 PM
To: [email protected]
Subject: [ham-amplifiers] Dummy Load Resistor

?

I'm wondering if a Planar resistor can be used for an RF dummy load. I have a couple 1KW 100 ohm Planar resistors and an 18# heat sink, I can't find my answer anywhere. Any information will be greatly appreciated.

 

Thanks for all the replies. I don't need a dummy load, I just have this stuff laying around. I'll probably just try for the heck of it. Again, thanks for the replies.
 

It would take the op all of 30 secs to parallel the 2 x 100 ohm resistors and see if they are inductive.? ?Heck only 1 is required for this test.??
 

If you use them (or it) for a dummy load, they (or it) will require a large heat sink.
? 73?? Bill K3HZP

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