NNTP-Posting-Date: Thu, 02 Jan 2003 20:40:57 -0600
From: Barry Lennox
Subject: Re: Resistors for r.f. applications
Date: Fri, 03 Jan 2003 15:42:58 +1300
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On Thu, 2 Jan 2003 22:20:10 +0000, John Woodgate
>I tried a web search for resistors that stay resistors, and about the
>same value, up to at least 10 MHz, but found it surprisingly difficult
>to find anything. I need some 50 ohm 0.5 W and some low values like 1
>ohm, very low power.
Carbon comp will do, but are a bit hard to find these days. Be wary
though, as different types of carbon comps behave diffently. We had a
225-400 MHz power amp (made by ITT, IIRC) that would only behave with
some brands of carbon comps, others would make it oscillate at the top
end. They looked identical, but were not!
SMD will also work well, take a look at http://emcesd.com/1ghzprob.htm
I have also used a 1.2 Ohm, 0603 SMD as a dummy squib, it was flat and
resistive to at least 1.6 GHz, the far bigger problem was the physical
transistion from coax to the SMD part. Just looked as I have a reel of
about 4999 of them!, they were from Newark and mfg by Xicon.