Tod - ID tod at k0to.us
Tue Feb 28 17:25:04 EST 2006

If someone is looking for rhombic resistors, I have one that has been in my
parts collection for more than 30 years. It is NIB. Koolohm  120NIT  120W
390 ohms. It is 9 inches long and 1 inch in diameter. Surplus Sales of
Nebraska has a display for Non-Inductive resistors that shows a picture of
this item. It is Type B. Their pricing is somewhat aggressive, however.

If someone wishes to acquire my resistor, for some reasonable price
{definitely less than Surplus Sales pricing} so they can store it in their
parts collection or even put it into service please contact me. I have
finally accepted that building a rhombic antenna is not going to be a part
of my amateur experience.

I suggest interested parties contact me off the reflector.

tod at k0to.us


> -----Original Message-----
> From: towertalk-bounces at contesting.com 
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Pat Barthelow
> Sent: Monday, February 27, 2006 4:54 PM
> To: fabio.grisafi at libero.it; towertalk at contesting.com
> Subject: Re: [TowerTalk] RHOMBIC RESISTORS
> Fabio,
> I know Caddock is a mfg of high power non inductive 
> resistors, perhaps they have what you need...
> I once had rhombic opportunities, and learned that you can 
> reduce the power handling reqts of the terminating resistor, 
> by createing a lossy, tapered transmission line, using 
> stainless steel wire, dropping from the far apex of the 
> rhombic down near ground level and doubling back towards the 
> center of the antenna.  If long enough, much of the power is 
> dissapated in the Stainless Steel (Nichrome)  transmission 
> line, and your terminating resistor can be of a smaller power 
> rating.  The military even eliminated the need for a resistor 
> at all, if you use a long enough lossy transmission line...
> Conventional construction with the resistor at the apex 
> requires substantially less power capacity than is input to 
> the antenna, due to power being radiated before arriving at 
> the resistor...Literature often mentions about 1/2 input 
> power for the resistor power rating.
> I think Jim Niger, N6TJ  is a professional who works with 
> rhombics on Islands in the Atlantic and would have a wealth 
> of knowledge....
> I have worked a few stations, one notably in New Zealand, 
> equipped with rhombics and was stunned at their performance.  
> A/B comparisons Rhombic pointed to West coast US, from ZL,  
> vs Hygain TH 6 at same height, profound; several uncalibrated 
> S units....
> 73, DX, de Pat AA6EG aa6eg at hotmail.coim
> >From: "Fabio Grisafi - IT9GSF" <fabio.grisafi at libero.it>
> >To: <towertalk at contesting.com>
> >Subject: [TowerTalk] RHOMBIC RESISTORS
> >Date: Tue, 28 Feb 2006 00:14:51 +0100
> >I wish to know how could I build non-inductive 600-800 Ohm 1KW 
> >resistors to use with rhombic antennas.
> >Thank you,
> >Fabio, IT9GSF.
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