Topband: Beverage Improvements?

[Tom Rauch]

Hi Hardy,

Everyone's soil is different, and what works well in one location or 
even at one time of the year might not apply to another location at 
another time of the year.

I'm a believer in measurements, and I certainly appreciate your 
work. I make the test in a slightly different manner. I am not 
interested in SWR on the feedline, but rather standing waves on 
the antenna because I want to maximize F/B ratio, not power 
transfer. 

With that in mind, I sweep the Beverage input and watch for SWR 
(or impedance) variation with frequency. When the impedance (or 
SWR) remains basically constant as frequency is varied, I know 
the antenna has the lowest standing waves. That clearly tells me 
the antenna is properly terminated. A very small impedance 
change with frequency, and/or minimum standing wave changes 
with frequency, also results in about the best F/B ratio.

We should all be cautious and not expect results at one location or 
even tests at one time of the year to agree with results everywhere 
every month of the year! 

For example, I initially accepted the fact that I could tolerate a 
single ground rod on my Beverages, based on the fact that I could 
adjust the termination resistors for a very small SWR change 
between 1.7 and 5 MHz. (BTW, this measurement MUST be made 
right at the Beverage, and not through a transmission line of more 
than a few feet). 

There seemed to be little difference in wet and dry weather 
performance, and I used a 390 ohm resistor.

However, a year later and we had a drought. F/B seemed worse, 
and I measured the antennas. Now I needed 270 ohms, and could 
never make the antennas quite as flat. I added two radials on each 
ground rod, and the resistor moved to about 450 ohms while SWR 
was once more mostly unchanging with frequency changes.

Since them it has rained quite a bit, and the antennas remain in 
adjustment.

I would never run a ground wire from end-to-end, I think that is a 
silly concept, but I learned the hard way my antennas are more 
stable with weather changes if I have more than just a few ground 
rods at each end. 

By the way, there are always frequencies where the SWR barely 
changes even if the antenna itself develops standing waves 
(indicated by standing wave changes with frequency changes). We 
have to be careful, and check SWR at several frequencies. 

What might be needed at some locations some times of the year 
might not be needed at other locations or at other times of the 
year, but a good ground will ALWAYS work and never be harmful. 

A single driven rod is lucky to be below 100 ohms on 160 meters in 
some soils, and that value will change considerably with soil 
conditions.

73, Tom W8JI
w8ji@contesting.com



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