Topband: Bury beverage wire?
donovanf at starpower.net
donovanf at starpower.net
Wed Jan 17 13:01:26 EST 2018
Matching transformers aren't necessary for your 160 meter Beverage
b ecause your coax is only five meters long, b ut its probably best to
use a pair of transformers. I ts likely that the loss in the matching
transformers will be very slightly greater than the mismatch loss
through only five meters of coax. If you don't use transformers,
use 75 ohm high velocity factor foam dielectric coax such as RG-6
cable TV coax.
If you use matching transformers, it isn't necessary to precisely
match them to the Beverage, a pair of 6:1 transformers will work fine
with 75 ohm coax. Because one dB of additional loss isn't a significant
consideration in a 160 meter Beverage, you can use either a binocular
core or toroid ferrite core with either isolated windings or auto
transformer winding. It isn't worth the trouble of building low
loss transmission line transformers for Beverage antennas.
The antenna side of each matching transformer must be connected to a
ground rod. Grounding the coax side of each transformer shouldn't
matter because the coax is so short. I'd ground the coax shields
since common mode isn't an issue with only five meters of coax.
My favorite Beverage transformer is the W8JI 2:5 turn ratio Beverage
matching transformer using a FairRite Products 2873000202 Type 73
ferrite binocular core. I use either telephone wire from an RJ-11
telephone cable, wire from a Cat 5 Ethernet cable or 30 AWG wirewrap
----- Original Message -----
From: "Martin" <dm4im at t-online.de>
To: topband at contesting.com
Sent: Wednesday, January 17, 2018 4:10:04 PM
Subject: Re: Topband: Bury beverage wire?
Thanks to all.
I had a few direct responses to my inquiry.
I should haver better described the situation by expressing that it is
not a driveway, but rather an opening in a fence separating 2 lawns. I
just had no words for it in english.
One guy came up with the idea to thread the wire through tennisballs and
bury it in a conduit, so no portion of the wire would touch ground or
This seems like a good idea, but isn't just burying coaxcable , leaving
the shield open and only use the center conductor about the same,
without a bunch of unknown parameters?
Another suggestion was to bury coax and start the antenna after the
opening. Excellent, but last resort, because this would only allow a
180m long antenna. Still better than no antenna and better than most
hams can do.
W3LPL came up with what i think is the best idea:
Bury coax with high VF and put transformers on both ends.
This leads to another question:
What ratio do i wind the transformers? 1:9 at the feedpiont, 9:1 at the
beginning of the coax, 1:9 at it's end where the wire continues? Or do i
measure the impedances to calculate a ratio?
Do i put in a ground rod at each end of the coax to connect the
Do i connect both sides of the transformers to ground?
If i get this to work, i have a 230m-235m long antenna with 5m of it
Ohne CW ist es nur CB..
73, Martin DM4iM
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