[TowerTalk] TH7-DX Balun

[TexasRF@aol.com]

In a message dated 2/23/2005 1:14:19 A.M. Central Standard Time,  
bjtatum at 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. at 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