[Amps] Caddock power resistors

[jeremy-ca]

Mouser has them at a bit over $9 in single qty. Go to the Caddock page, 
click on distributors and then Mouser. Scroll down to the value/wattage you 
want. Or maybe just go to Mouser and type Caddock.

Carl
KM1H




----- Original Message ----- 
From: "Rod Elliott" <wultabat at xplornet.com>
To: <amps at contesting.com>
Sent: Tuesday, November 13, 2007 3:00 PM
Subject: Re: [Amps] Caddock power resistors


> At 19:14 11/13/2007, you wrote:
>>[snip]
>>I used some Caddock power resistors in the grid circuit of the
>>"Sunnyvale/Saint Petersburg Kilowatt Plus" that appears in the 1999-
>>2004 ARRL handbooks.  They are mounted on a pretty big heat sink, and
>>have their own fan.  This setup has been very satisfactory, and
>>capacitance hasn't been a problem.
>
> I did a ballpark calculation of the capacitance of one Caddock MP9100
> unit, and came up with 5pf. Using that value with their specified
> inductance of 20nH gives a self-resonant frequency in the order of 500 
> MHz.
>
> Wiring four of these units in series/parallel would produce a 400
> watt power rating. If mounted taking great care to minimize lead
> lengths, the self resonant frequency of that array would not be much
> lower than that of a single unit. Should be able to use these at HF
> without compensation.
>
> Interesting!  Anybody know what these units cost? ... couldn't find
> them in my DigiKey catalog
>
> Cheers
> Rod VE3UW
>
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