Hello Bob and all, Yes I agree on the issue of needing the stable impedance
from the elements to drive the passive systems. I still have some questions
in my mind about the radials and here is why. I have made many field tests
where I measured the actual phase and amplitude differences between two
receiving elements where one is held constant and parameters around the
other were changed such as ground rods, radials, and such. Both were
receiving signal from an equidistant transmitted source. What I can tell you
for sure about this is that with a Hi-Z system the phase and amplitude shifts
become quite unstable when radials are used. I do not know this to be a
fact with loaded elements but I have seen evidence of some received
signal shift due to the presence of the radials to the element. This test
really
opened my eyes about received signals and what objects might affect
them. I have plans to buy the NEC4 engine and do some more field tests
using another technology that should give me more answers. It is these
minute details that prevent us from making these RX antennas even smaller.
There is no doubt that the state of the art is advancing in receiving antenas
with all the work that is and has gone on. I am confident that what we are
presently doing is not perfect and I expect the state of the art still has a
ways
to go. There have been many man years of work by many people. I hesitate
to name calls but a few notables are K6SE, W7IUV, W8JI, K9AY, W3LPL,
W5ZN, W1FV, NX4D, N4IS, AA7J, K1LT and many many others that I
apologize for not having the space here or personal memory at the moment
to mention. There are more man years of work to do.
I still covet the 96 element Wullenwever antenna invented around 1940!
Lee K7TJR
>The issue is getting sufficient ground radials so that changing soil
>conditions: dry season, wet season, etc have minimal impact on the impedance
>which is the easiest measurement of the changing conditions. Joel and I did
>measurements several times and when he was near drought he found he had to add
>radials to stabilize the performance. Once done, his system has been stable
>since.
Great news on both of you successfully deploying.
Bob
>N4HY
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Topband Reflector
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