To All:
A controversial subject.........
About last August I decided to see if I could improve my receiving
capabilities on 160 mtrs. I have 5 Beverages but they are short in
comparison to what is really needed on 160; 2 are 330 ft. and 3 are 415 ft.
This is all I have room for since "civilization" has grown up around me. I
had read that putting in more grounds at each end of a Beverage would
improve the F/B ratio and that connecting the ground rods together by
running a wire on the ground between the input and output of the Beverage
was also a good thing to do. Well, I did all that and I did not notice that
things got any better or any worse. Everything was pretty much as usual.
The thought then occurred to me that if anything changed in the Beverages
it sure had to be the input impedance since that parameter is very
sensitive to minor changes in any antenna. I am fortunate to own an HP8753B
Network Analyzer (a requirement for my work).
I calibrated the analyzer at the input to the 9:1 transformer and ran the
following impedance measurements:
1) Measurements were made with 1, then 2, then 3, then 4 ground rods
connected at each end. #1 rod is 6 ft. copper plumbing pipe, the rest of
the rods are 3'4" copper plumbing pipe spaced 2 ft around the first rod.
2) Measurements were then made with a wire running along the ground
connecting the ground rods vs no wire at all. The wire was #24 insulated.
3) Four frequencies were tabulated, 1.8, 1.9, 3.6, and 7 Mhz.
330 ft. East Beverage
F 1 rod 2 rods 3 rods 4 rods
1.8 44.5+j8.6 44.2+j8.8 44.2+j8.7 44.0+j8.8
1.9 45.5+j11.2 45.3+11.3 45.4+j11.2 45.4+j11.2
3.6 39.7-j1.4 39.7-j1.7 39.7-j2.1 39.7-j2.2
7.0 50.3-j0.2 49.4-j0.2 49.0-j1.0 48.9-j0.9
415 ft. Northeast Beverage
F 1 rod 2 rods 3 rods 4 rods
1.8 51.6-j9.2 51.4-j9.5 51.4-j10.1 51.2-j10.5
1.9 47.7-j9.6 47.5-j10.0 47.3-j10.6 47.0-j11.0
3.6 50.8-j2.6 50.8-j3.1 50.5-j3.2 50.6-j3.7
7.0 29.7+j2.3 28.9+j0.8 28.8+j0.5 28.9+j0.2
330 ft East Beverage, new termination resistor, 450 ohms
F 4 rods without wire 4 rods with wire
1.8 46.1-j4.7 45.3-j3.0
1.9 42.8-j3.1 43.3-j1.4
3.6 29.7+j0.1 30.0+j0.4
7.0 42.0+j6.1 40.9+j6.7
All impedances were rounded off to the nearest 0.1 ohm (In reality, the
753 measurements jump around +/- 1 ohm.)
An examination of the two tables reveals that nothing really changed when
extra ground rods were added! The same goes for the wire on the ground.
After I saw the results tabulated, I didn't bother doing the other 3
Beverages.
Believe me, I was just taking data and did not realize that the
measurements were
that close together.
If someone has had a good experience putting in extra grounds and tying
them together with a ground wire, please let me know. But as far as I'm
concerned, I went to a lot of work and expense for nothing.
Hardy N7RT
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