I still have two Telrex 10 meter monobanders (a 3 el and a 5 el at 65 ft
and 35 ft) that are part of a 3 high stack. They both have T-Matches
with coaxial baluns. I'm running maximum legal power to a 160 meter
Omega match on the 45G 100 ft tower that these antennas are on.
In my particular situation I have not had any baluns fail as yet.
However every situation is different. The driven elements are insulated
from the boom on both of the antennas.
73,
John, W4NU
On 12/26/2012 2:13 PM, Tom W8JI wrote:
Anyone have problems running a KLM antenna with the 4:! balun and
elements insulated from the boom (stock KLM config) on a shunt fed
tower for 160? I ask because I have a 6 element 10 on the top of my
shunt fed tower and now, after running a kw on 160, the antenna's swr
has gone over 2:1 where before it was pretty flat at about 1.2:1 or
so. Any ideas?
You probably ruined the balun from 160 current. The best cure would be
installation of RF chokes from elements to boom on all of the
elements. Anything over a few dozen ohms on 10 meters works for the
parasitic elements. They are not critical.
For 10 meters, I would use a good 4:1 voltage balun with the coax
grounded to the boom, or you can use a 4:1 current balun if you use a
center tapped choke of at least 1000 ohms and less than 2000 ohms on
ten meters with tight mutual coupling across the winding.
It would not be difficult to build some.
Remember the half-wave of coax makes a voltage balun, so you might as
well just save space and get more bandwidth by using a standard
compact 4:1 voltage balun.
73 Tom
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Stew Perry Topband Distance Challenge coming on December 29th.
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Stew Perry Topband Distance Challenge coming on December 29th.
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