Hi, Jim.
Well, by "RF ground" I meant the conductive (actually semiconductive)
zone of the earth as seen by the incoming RF relative to the wire.
"Ground" is the same term used in modeling programs like EZNEC, and I
qualified it by saying RF since the conductivity is different at RF (HF)
than, for example, DC or power line AC. I certainly did not mean in the
context of an infinite source or sink of electrons like some folks seem
to think exists.
I could have been more precise, though.
73,
Dave AB7E
On 8/31/2021 10:00 PM, Jim Brown wrote:
Good analysis, Dave. Beverages depend on lossy soil underneath them to
work, and, as we all know, soil varies widely from place to place, and
even locally. I have very poor (rocky) soil, and the terrain under it
in my woods is quite irregular. For example, my EU/VK reversible Bev
starts at about 5 ft, running over the earth that drops gradually and
then more steeply to to a creek, losing about 30 ft of elevation, then
climbing up a steep rise to its termination point. Over that run, it's
height above ground varies from five feet to 10-12 feet. For most of
its length, it's held up by laying on top of brush.
As 160M super-op has often said, "any Beverage is better than no
Beverage." His run through terrain at least as irregular as mine, and
he's deep in a ravine!
I do, however, object to "RF ground," and so do authorities like N0AX
and K6WX.
73, Jim K9YC
On 8/31/2021 7:58 PM, David Gilbert wrote:
Since actual RF ground could be almost anywhere (and could be
definitive or graded) depending upon your soil, practically speaking
the difference between 12' and 10' is a meaningless distinction.
The height above actual ground will of course moderately affect the
input impedance, but you're not going to know what that is ahead of
time and to be rigorous you would want to adjust the terminating
resistance for a more or less constant impedance as a function of
frequency ... and then set the turns ratio of the coupling
transformer to match.
Personally, I think being THAT rigorous isn't all that rational. Put
your wire at 12' and use whatever input transformer and termination
you already planned.
73,
Dave AB7E
On 8/31/2021 5:56 PM, RVZ via TowerTalk wrote:
Wondering if anyone has had good success with a Beverage mounted 12'
above ground? 12' is the minimum clearance I need to safely clear a
drive way. Please reply direct as I hope to install tomorrow.
Thanks in advance for your reply! 73, Dick- K9OMRLVZ@aol.com
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