TopBand: Beverage terminating resistor

[Earl W Cunningham]

John, K9UWA wrote:

>Earl what about 4 foot high beverages...can we safely say that the 
>height to termination resistance ratio is linear????
==================
Hi John,

I lowered the same 580' Beverage to 4' and came up with the following:

Very good soil:
     Termination for best skywave F/B (33 deg) = 580 ohms (22 dB)
     Termination for best F/B at 5 deg = 660 ohms

Good soil:
     Termination for best skywave F/B (31 deg) = 560 ohms (35 dB)
     Termination for best F/B at 5 deg = 585 ohms

Poor soil:
     Termination for best skywave F/B (32 deg) = 500 ohms (24 dB)
     Termination for best F/B at 5 deg = 550 ohms

Very poor soil:
     Termination for best skywave F/B (34 deg) = 310 ohms (19 dB)
     Termination for best F/B at 5 deg = 390 ohms

This time I took greater care in determining the optimum termination
resistances.

The skywave angles shown above are the angles of maximum reception in the
forward direction.  Curiously, these angles are a few degrees lower than
for a 10' high Beverage.

For the 10' high Beverage, I merely viewed the elevation pattern to
"determine" the best termination for low-angle (groundwave) rejection to
the rear.  For the 4' high Beverage, I used the calculated F/B at a 5
degree vertical angle.

At 4', the Beverage over "good" soil is the best performer with 35 dB F/B
and the lowest angle (31 deg).  At 10', the Beverage over "very poor"
soil is the best performer with 35 dB F/B and lowest angle (33 deg).

To answer your query, no, the termination value does not appear to
linearally change with changing heights.

Whether modeling Beverage antennas yields accurate results or not is a
moot point.  However, modeling them at different heights does show a
definite trend.

73, de Earl, K6SE


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