Topband: "Grounds" for a Beverge
Guy Olinger K2AV
olinger at bellsouth.net
Tue Jan 18 06:46:08 PST 2011
Some grounds can be horrific. 500 ohms is horrific and atypical unless we
are talking about sand or extremely dry material. BUT even a 500 ohm ground
at the feed would be in series with a 450 ohm-ish characteristic impedance
of the beverage. Improving the ground "only" to a fairly bad 50 ohms would
improve the signal level by 3 db, but may not do a blessed thing to the
signal to noise ratio that it was receiving, which is the ONLY point of
having a beverage. Since RX antennas are low level, that 3 db change will
make no difference.
Non-functional results in beverages are almost always connection or damaged
feedline issues, or trying to use them around salt-water. An example of
connection problems, there is a ground at the feed point, but the connection
between the wire to ground and the ground itself has become corroded. The
resistance to ground as measured to either side of the connection with an
ohmmeter is ~400,000 ohms and varying.
On Mon, Jan 17, 2011 at 12:44 PM, Charles W. Shaw <chasshaw at leaco.net>wrote:
> Howdy from NM,
> It appears to me that once more the term "ground" has led
> someone astray, and most likely it was some of us old time Topbanders
> that caused it.
> Mark, WD4ELG, recently said, "I thought bev worked with poor
> ground." In one sense, most of us would agree--a Beverage over dry
> sand and rock can work OK and certainly better than if it's over salt
> water. But Mark was discussing the "ground" stakes of his Beverage.
> I have often read that the terminating "ground" at the far
> end of a Beverage is not very critical. However, I believe that we
> should strive for a good "ground" at the feeder end. My reasoning is
> that unless we have a relatively low resistance "ground" on the
> antenna side of the impedance-matching transformer, the current
> through the transformer will be reduced so that little signal will
> reach the 50-Ohm primary going to the receiver.
> OK you antenna expert EE's, set this musician MusEd ham straight.
> Charles - N5UL
> Hobbs, NM
> UR RST IS ... ... ..9 QSB QSB - hw? BK
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