I have heard ferrite type stuff can cause nasty problems at high power.
Since I run tube rigs, I think I will just cut a dipole for the center of 80
meters, and ditch the tuner, which gets quite warm on the G5RV.
If I am going to heat something up, it might be better that its not in a
shielded metal box.
While a balanced setup is best, I don't want to have to tune the antenna every
time I change frequencies, as I like to hop around between bands and the phone
and CW parts of the bands..
Without a tuner, you can use the antenna's on receive, even on other bands,
while with a tuner, if you get far from where you are tuned from, you get a lot
of loss...
Brett
----- Original Message -----
From: Jim Wilhite
To: Discussion of AM Radio in the Amateur Service
Sent: Monday, January 12, 2009 6:46 PM
Subject: Re: [AMRadio] 160 meter antenna
Remember what balun means, balanced to unbalanced. This is not some magic
device to withstand grand excursion from center frequency of an antenna. It is
to transform on impedance to another. If you move far enough off center you
can wind up with very high voltage in the balun, resulting in what Brett
describes.
Probably the best balun for high power is the choke balun wound on 6" PVC of
RG 8U or the beads that fit over the coax. Since supporting the choke balun
at the center of my antenna would be a challenge, I use the beads. There are
there to prevent current of the shield of my coax feedline when I am far off
center frequency of the antenna.
If you are going to move more than 3% of frequency, then forget the W2AU or,
even, the so called quality type of balun. The W2AU I took apart was
constructed of RG 58. Not the best for a HV environment. When you move from
one end of the band to the other, just use a good high power tuner and be
prepared for lost power in the tuner.
Jim/W5JO
----- Original Message -----
If you run any power at all, forget the balun unless you gat some sort of
monster one, the usual suspects wont work for even moderate power AM.
Any time I tried traps or baluns on AM, all I got was a fire.
Some might take 50 watts carrier, but the DX100 blew out many a trap back
when I was starting out in AM.
Brett
N2DTS
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