When I haven't had time or proper materials to wind my own, I've used Balun
Designs www.balundesigns.com because (1) he's significantly less expensive
than his competitors, (2) he's a student of and follows the engineering
findings of the late W2FMI Jerry Sevick (author of "Understanding, Building,
and Using Baluns and Ununs" published by CQ Communications), (3) he uses the
proper quality materials, (4) he'll custom build to your specs if needed.
First, tho, I urge you to either replace the 25ft twin lead you have with
31ft (preferably 450 ohm ladder, but you can continue to use 300 ohm flat
lead satisfactorily), and you should find that the antenna performs
significantly better (this assumes that the antenna wire length is 102ft
total). The feedpoint to the twin/ladder line should then be about 50-60
ohms impedance. You'll need at least 70ft of coax connected to that
feedpoint for the antenna to perform properly, regardless of balun (ideally,
coil extra unneeded length close to the feedpoint). It is possible to
operate the antenna without a balun, as some hams do, but operation will not
be optimal and you'll need a good tuner.
A "current" balun is the best type to use with a G5RV (Guanella design is
best), which will serve to keep unbalanced RF current off of the coax
shield. The 4:1 you currently have on it is way too high ratio; a 1:1 would
be the proper ratio to use. My bet is that your antenna tuner is stressed
with that balun presently, and the system's not performing optimally.
Stephen W9SK
Two Rivers School SCR Host
(we'll be on the air Feb2013 SCR)
North Bend, WA
CN97cl
-----Original Message-----
From: Antennaware [mailto:antennaware-bounces@contesting.com] On Behalf Of
John
Sent: Wednesday, February 06, 2013 10:23 AM
To: antennaware@contesting.com
Subject: [Antennaware] G5RV balun question
I have a G5RV type antenna I homebrewed. It is around 100 feet long, fed in
the center with around 25 feet Radio Shack twin lead (300ohm).
At the end of the twin lead is currently a HI-Q brand 4:1 voltage balun, and
then a run of 75ohm coax to the shack. I want to replace the balun with
something that will keep RF off of the coax shield-I understand I need a
current balun for this. What are the best brands and models to use for
this?
73 John AF5CC
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