In a message dated 2/23/2005 1:14:19 A.M. Central Standard Time,
bjtatum@ev1.net writes:
I have been away for a few days but noticed a few subject lines covering the
TH7-DX balun, the BN-86. I have a TH7-DX that will be going up in near
future, what is the best balun to use for it? I know that when I assemble it I
will use the updated assembly notes for better 10 meter performance, but what
about the BN-86 balun, is it the best one to use? Thanks, _Byron._
(mailto:Byron.@contesting.com)
Like a lot of questions, this one has more than one answer. A TH7DX (or was
it TH11?)question came up recently about a non Hygain balun having higher vswr
than the Hygain balun. It is not commonly known that the longish leads
(factory made) connecting the Hygain baluns to the feed point form a short, hi
z
transmission line that distort the R +j values present at the feed point.
Apparently this effect was included in the overall design of these Hygain beams
as the vswr is fine when a Hygain balun is used.
A previous post mentioned that the original BN86 was designed back in the
1000w/2000w pep days and this is certainly the case. The biggest killer of the
BN86 was accidentally firing up a big amplifier on the wrong band, which makes
the vswr extremely high, and flashing over between windings in the balun.
The newer BN4000 is far more robust than the old balun, being made of a length
of Teflon dielectric coax with ferrite chokes over the shield all stuffed
inside the original BN86 sized enclosure..
The BN4000 mounts using original hardware, takes care of the flash over
problem, withstands higher power and takes care of the long lead tuning issue
all
in one easy step. Therefore; I suggest that the BN4000 is the best solution.
New TH11DX antennas are being shipped with the BN4000, for a reason unknown
to me, the TH7DX shows the BN86 included and BN4000 optional.
The BN4000 baluns are available for $99 at Texas Towers and can be shipped
in about ten minutes. Please call 1 800 272 3467 or _www.texastowers.com_
(http://www.texastowers.com) to order.
I will leave the second best answer to someone else.
73,
Gerald K5GW
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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