[Amps] Non-inductive Resistors

JMLTINC at aol.com JMLTINC at aol.com
Fri Feb 9 15:00:42 EST 2007


John,
I would ask this question of Ohmite about their OX/OY  series ceramic 
composition resistors.  Last time I asked them by  posting a request on 
their WEB site, they got back to me in a couple of  days.  See 
www.ohmite.com.

Mike, W1NR
Thanks, Mike. I did that today. Hopefully they  will give me an answer!
 
Hi John....

You didn't say what power level you were considering but  I see in the 
Mouser catalog
that they have Caddok power film resistors  from 15-100 watts. Says they 
are good
up to 500 mHz. These look similar  to TO-220 transistors.

73, Roger
Thanks, Roger. I am not sure of the power level  - somewhere < 15W. These are 
grid swamping resistors and the actual  resistance value (and therefore power 
dissipation) will have to be determined by  experimentation.

I think it's unusual to want/need grid  loading at UHF. Given the 
reactances in typical tubes, is 1k going to have  much effect?

At resistances up to 1-200 ohms you can get low inductance  in the 
stripline resistors made by RF Power/Anaren, EMC, KDI, Florida Labs  and 
suchlike (some of these might be history).

Can you tell us more  about the design?

Steve
 
Yes Steve. It is a K2RIW amplifier and is used  for ATV. I am trying to 
broadband the input to enhance a poor sound sub-carrier.  I am not sure how much 
loading it will require (or whether it will improve the  situation adequately). 
Right now the amp is swamped with 10K a side. I will try  2K and go down from 
there. 
 
Thanks to all who responded. In the old  days, carbon comp was the only game 
in town. Today, there are too many new  products, and they have left me behind 
on the knowledge game. 
 
My original question  was:

At 07:39 AM 2/8/2007 -0500, you  wrote:
>
>Hello all,
>
>Am looking to load a 70cm  amplifier grid with about 1K or less of 
resistance.
>
>This has  probably been asked before, but what types of "non-inductive" 
>resistors  are non-inducive up to 1 GHz? And, if carbon composition is the 
>only  choice, where can you find 3W these days?
>
>I have found some  sources state carbon film and metal film resistors are 
>non-inductive,  but rate them to 100 MHz.
>
>Thanks,
>-John,  N9RF


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