[TowerTalk] Cutting a FT-240 type 33...in half ??

[Jim Thomson]

It’s a thick walled  plastic nema box.... and toroids are  type 31, not type 
33.
7-17 female connectors on each end.   Existing chokes consist of 4 turns of 
393
through 4 x type 31 cores.   Steve, G3TXQ tried 4 x turns of 213 through 4 x 
cores and
found the Z was a little over 3 k ohms  from 13-27 mhz.   I need to use one 
box for 15m,
and  the 2nd box for 20m.  Without mucking it up too much, I believe I can 
add at least
one more core, perhaps 2 cores  to the 15M box....and possibly 2-4 
additional  cores
to the 20m box.

I also need to build two more boxes, one for 80m, and the 2nd for 40m. 
These are all monoband
chokes, so they only have to work good one one band.   I think the max turns 
that can be stuffed through
these 1.4 inch ID cores is aprx 5-7 ?   393 coax is is bit smaller OD  vs 
213.  .391 inch vs .405 inch.

Something else I cant fathom is the use of cores on both sides of the coax 
loop.  IE:  3-5 x cores
at 9 oclock position...and 3-5 at the 3 oclock position...... vs 6-10 cores 
all stacked on one side.
K9YC sez  the binocular format is not optimum.  I just don’t understand why. 
I only have so much
room in these nema boxes...  so cant have huge loops on the outside of the 
cores.   I also cant
have loads of space between the loops on the outside.   I can only cram so 
many torroids in there
and only on one side.  Think it was like 6-7 max.   Im also trying to 
extrapolate K9YCs  info, plus factor in
tight turns, with no space between em.   6-7 x cores  + 5-7 turns might do 
the trick for either, or 80
and 40m.    I need to optimize  for 80 and also 40m, separate chokes, the 
best I can, with the
constraints I have.

Jim  VE7RF


-----Original Message----- 
From: Ian White
Sent: Monday, February 09, 2015 11:42 PM
To: 'Jim Thomson' ; towertalk at contesting.com
Subject: RE: [TowerTalk] Cutting a FT-240 type 33...in half ??

Hold on, Jim -

Please say that <isn't> a metal NEMA box with flange connectors at both
ends?


73 from Ian GM3SEK


>-----Original Message-----
>From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
>Jim Thomson
>Sent: 10 February 2015 05:56
>To: towertalk at contesting.com
>Subject: [TowerTalk] Cutting a FT-240 type 33...in half ??
>
>Ok, I have a requirement where an additional  one or two x  2.4 inch
OD,
>type 33 cores needs  to be added to  an existing choke balun.
>Since each end of the RG-393 silver plated + teflon coax is already
silver
>soldered to a 7-16 DIN connector  at each end of the nema box,
>I would rather not have to take the entire assy apart.  Major pita.
393 coax
>has TWO  silver plated braids, and in this case, each of the braids has
been
>carefully
>separated at each end, and each braid is silver soldered to a lug,
that is
>bolted to  the 7-16 din connector flange, via the SS  8-32 machine
screws.
>IE: 2 of the 4 corners of each 7-16 din female coax connector gets a
braid
>attachment.
>
>Can a 2.4 inch OD, 1.4 inch ID, type 33 toroid  be cut in half, edges
sanded,
>then  placed around the existing  4-5 turns of 393 coax, then
>held together via glue, ty-raps, both, or some other method ???   I
have an
>excellent H-V bandsaw, made for cutting steel, hard steel, and AL.
>IE: 80-120-200 ft per minute.   It would slice through a toroid very
quickly.
>If what I propose is feasible, it would save me a lot of grief.
>I already checked, and the big, type 43 snap on types  will not fit,
since they
>only have a 1 inch ID.
>
>Tnx...... Jim   VE7RF
>
>
>
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