[TowerTalk] Fwd: Another one off balun capacitance question.

[Hans Hammarquist via TowerTalk]

The advantages of separate the cores is that you enhance the cooling. The cores will not get so hot as you allow for more air flowing past. You will increase the capacitance as you will need more wire.


Hans - N2JFS



-----Original Message-----
From: Roger (K8RI) on TT <K8RI-on-TowerTalk at tm.net>
To: towertalk <towertalk at contesting.com>
Sent: Sat, Nov 1, 2014 1:15 am
Subject: [TowerTalk] Another one off balun capacitance question.


I asked this before but with a bit different wording.

What about core spacing in a multi core balun?    I have 6 and 7 core 
baluns with 6 and 7 turns of coax.  I'd have to look up the coax 
designation, but it's roughly 1/4" OD with a Teflon dielectric and 
silver plated shield braid. I'll be running the legal limit into a 160 
half sloper with the balun at the feed point.

I have one set with the cores super glued together in a stack and am 
building another set with 1/4" spacing between the cores.  With the 1/4 
inch spacing, I just mill 1/8th inch deep slots in 1/4" plexiglass the 
width of the core thickness and a 1/4 inch spacing between the slots.  I 
use a rather thin epoxy to wet the surface of those slots and slide them 
into place.  Yes it's fragile and I'm looking at Lexan.

The coax is epoxied to the inside of the cores and held within an inch 
of the OD using a ventilated sleeve. (thin wall plastic sewer pipe)  
Overall, the coax spacing to the core will be much less than in many 
choke baluns.
I use a piece of 1" X 1/8th inch Aluminum angle set in "V-blocks" to 
line up the cores while waiting for the epoxy to set.  I use the same 
set up when sticking the cores together with super glue.  Just 3 or 4 
"small" drops spread out is plenty and has less risk of your fingers 
becoming a permanent part of the cores..

"I think" the cores spaced 1/4" will give less C...maybe.   The area of 
coax to cores is the same on the inside although the cores are close 
spaced in one instance and have a 1/4" spacing in the other although the 
surface  area is the same.

   73

Roger (K8RI)


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