Hilltop vs. flat land enhances and lowers the TOA, which roughly
tribander at 60 - 80 ft is close in performance to 2 or 3 stack at 200
ft. Plus the hill - elevation brings one closer to the propagating
layers and less noise. There was W3??? in the past with tribander on a
hill that was dominating 20m.
Oceanfront, salty ground typically ads about 15 dB especially with
verticals. Low angle, close to horizon, on RX and TX plus no noise
sources from the ocean, can't be beaten. Just get into the mobile and
drive around, in and out from the beach or on the bridge over salty
water. Like driving into the amplifier.
It took me while to realize that:
1. Antenna system - design, configuration, shapes the pattern and
contributes to efficiency of converting energy from the coax to be
radiated. Radiator with elevated radials in resonant antenna is good
example.
2. "Mirror" - Environment in which antenna system is positioned affects
the performance, efficiency and pattern shaping. Ground conductivity,
terrain, obstacles can have detrimental effect, distort or enhance
performance of antenna system. Picture light source and various mirrors,
from perfectly reflecting one, to "spongy", to absorbing one.
For example on low bands and 160, RF penetration into the ground is
deep. Portion of RF gets "eaten" by lossy dirt, rest is participating in
pattern forming. Remedy is to use elevated radials and have extensive
screen or radial field, as large as possible, to reflect the RF rather
than have it "eaten".
This is where some confusion about buried radials and number of them is
so live. Transition from few radials - antenna part to many - ground
screen/mirror. One has to distinguish between the "mirror" vs. antenna -
signal source and their mutual interaction. This is where salty water
shines, it is almost perfect mirror, with hardly any penetration, in
perfect harmony with RF radiator. I used to water the lawn before the
contest.
At old AT&T WOO site, the radio engineers in the thirties designed
conical monopoles sitting in the salty marsh by having base of antenna
elevated about 4 ft, about 30 radials going out in the air for about 15
ft to wooden "fence" and then dropping into the salty marsh. Whole
antenna field (abt 200 acres) is flooded through channels at high tide,
with portion of water evaporating and slowly increasing salt
concentration. S-meter on 160 sits at 1.
Buildings, power lines, trees can distort the "mirror" further and have
impact on antennas and pattern forming. Back in Toronto we have seen
dramatic effect of huge power line corridor, typically 2 - 3 S-units,
between my and VE3FFA QTH, being on opposite sides of the wires.
Keeping in mind that we are dealing with "light," it's beam shaping and
"mirror" helps to realize the important factors in the RF radiation
efficiency and beam shaping.
Happy and prosperous 2015!
Yuri, K3BU.us
On Thu, Jan 01, 2015 at 10:46 PM, ScottW3TX@verizon.net wrote:
> Is there an argument to be made for favoring plain vanilla flat land
in all directions, instead of a hill or mountaintop, so that the TOA's
can be optimized for all bands by antenna height/stacking for all
important directions?
Best regards,
Scott w3tx
On Jan 1, 2015, at 8:25 PM, "Ed Sawyer" wrote:
Go with the hilltop. The oceanfront is great if you have unobstructed
low
angle in a few favored directions. But oceanfront with low angles cut
off
is not a good compromise.
Spend A LOT of time with HFTA after carefully detailing the terrain
within
1000ft of the antennas. My best antennas are all 25 - 30 ft to Europe
off
the side of my hill to Europe.
Ed N1UR
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