At 08:49 PM 7/24/2006, Felipe Ceglia wrote:
>... RGc-6 and RGc-11 75 ohm catv coaxial cable... if it is possible to
>make snake beverages with these cable instead of 50 ohm.
Felipe,
(I have not yet put up any kind of Beverage - I just moved to a place that
has the room three weeks ago.)
I was reading ON4UN's book yesterday, including the section on snake
antennas, or "BOGs", Beverages On the Ground. I remember these points:
1) They should work well, and are recommended if you can't put up the
supports for a Beverage in the air.
2) They can be expected to deliver signal strengths 8 to 10 db less than
the normal Beverage. Thus a preamplifier may be needed.
3) Because of the lower signal levels, de-coupling the feed line is
very important: Common mode signals (the feed line outside conductor
acting as another antenna) are even more troublesome than with normal
Beverages. Do not ground the shield at the antenna feed point, use choke
beads on the feed line, in at least one location, possibly more, and ground
the feed line outer conductor at least 5 meters from the antenna feed point.
4) If you use coax as you indicate, a bi-directional antenna is possible,
with the signal from the far end of the antenna returning through the
inside of the coax.
5) Lew McCoy published information about antennas on the ground. ON4UN
states that none of the configurations described by McCoy in the
referenced publication will work as a Beverage.
6) Use of 50 or 75 ohm coax, at least in the feedline, makes no difference
whatsoever. Using coax that is well shielded DOES make a difference. Some
coax has very poor shielding and should be avoided for sure.
7) (?) The velocity factor may be influenced by the ground, so if you are
attempting to find a "sweet spot" in the length, take this into account.
I suggest you put your antenna out and let us know how it works.
Roy
- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
NEW: 13033 Downey Mill Road
Lovettsville, VA 20180
Phone 540-822-5911
Cell 301-928-7794
Work: Voice: 301-975-3254, Fax: 301-975-6097
roy.morgan@nist.gov --
Old address: 7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828
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