[TowerTalk] RHOMBIC RESISTORS

[Pat Barthelow]

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.