Another useful product line is heat-sinkable film resistors from Caddock
Electronics, Inc. These were covered in detail by Rick Littlefield,
K1BQT in the Quarterly Devices feature of Communications Quarterly,
Summer, 1995.
The Kool-Tab MP800 series components come in 8, 16, 20, 25 and 50 watt
ratings in TO-126, TO-220 and TO-220 with mounting tab packages in
values from .02 to 10K ohms, and are rated according to those packages.
MP820 and MP850 50 ohm devices are shown with VSWR<1.1 at frequencies
from 100 to 400 MHz. Their dissipation ratings vary from 2.25W in free
air to 6.5/7 W with large extruded heatsinks to 14W on a 5x7x2"
aluminum chassis.
These components appear to be very useful for HF/VHF applications! I was
introduced to these parts by George Badger, W6TC of Svetlana Electron
Devices as possible passive grid terminations for a grid-driven AB1
linear.
I have no connection with either Caddock or Svetlana.
Garry, NI6T
km1h @ juno.com wrote:
>
> I have been paging thru the new Newark catalog and came across a few
> interesting items that are "new" to me.
>
> Ohmite 50 and 100W non inductive resistors, including 50 Ohms. The caveat
> is that they give an inductance rating! That would lead me to assume
> that they are not HF RF rated but maybe for LF, audio and switcher
> supplies. Anyway the 50W is rated at 0.8uh and the 100W at 1.6uh.
> Has anyone experimented with these at HF, tuning out the XL, etc. ? The
> prices are a reasonable $9.19 and $16.81 respectively.
>
> The other item were non inductive Cermet power resistors by Spectrol.
> They are available in 500, 1K, 2K Ohm, etc and rated at 20W. Also rated
> at 1KV and 5KV dielectric strength. Made for PS use and the
> "Telecommunications Industry".
> Again probably not RF rated but just maybe useable as Beverage
> terminators with a simple capacitor tweak. At only $1.25 each they may
> be the answer to blown 1 and 2W carbons from static and coupled RF from
> the TX antenna.
>
> 73...Carl KM1H.
>
--
Garry Shapiro, NI6T
Visit the Northern California DX Club home page:
http://www.ncdxc.org
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|