[TowerTalk] TH7DX Balun Was W1JR, Now BN-86

[Jim W7RY]

Well team....


I know we tossed this one to death many times before... But here is what I 
just found on my TH7.

I installed a home brew W1JR type balun on my TH7 when I put the antenna up 
last year. I was not happy with the SWR curves when I tested the antenna 
after installation. I finally decided to do something about it.

I just removed the W1JR type balun and installed a Hy-Gain BN-86.

The SWR curves now measure about the same as what is spelled out in the 
manual. Before, the SWR on 20 meters was never below 2:1. And on 15, it was 
never lower than 2.5:1 anywhere in the band.


When I was testing the W1JR type with  my MFJ 259 on top of the tower, I 
noticed that the impedance would never drop below 40 Ohms. With the BN-86, 
now it will.

The W1JR balun is home brew. 7 turns of RG-142 on a FT-240-61 core wound 
all on the same side of the core. Not a cross over type winding.

The balun was installed into an outdoor plastic electrical box with brass 
studs through the sides for hooking to the matching section of the TH7. I 
used the same RG-213 coax jumper from the end of my 1/2" Heliax to the 
balun. No other changes... Just replaced the balun.

I know that Steve, K7LXC, mentioned in the tri-bander report that they had 
some difficulty with the balun selection on the TH7.


Hmmmmmm....

73
Jim W7RY