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

[Roger (K8RI) on TT]

The only way to cut a core, neatly is with an abrasive saw.  I think 
they'd eat the teeth right off a band saw blade.  Diamond is better yet, 
but my memory of magnetics is a gap is a gap, no matter how small. I 
don't think it'd have a big effect, but there's likely someone who 
remembers/knows these characteristics better than I.

HOWEVER. if you are going to add two cores or even one core, it's going 
to require more coax, or fewer turns,  (unless the current choke is 
wound very loose.) fewer turns means much less resistance, or isolation.
Even cutting them, I doubt I could add even 1 core to mine.  I am 
winding one that spaces the cores a 1/4" using Lexan spacers.  I should 
have it on the web site before long. That one, I could probably add two 
cores by cutting the space to an 1/8th or 1/16th inch.  It'd be a real 
PITA though as the cores are epoxied to the Lexan and I'd have to make 
new spacers. Lexan is expensive.
.
Were it me, I'd just pull the thing out, get some more coax and wind a 
new one. It will be neater and most likely, more effective.  I'm doing 
that with an AV640 matching network for the transformer and choke. 
Possibly an R8.  Several R5s and R8s in the area and all required 
rewinding the transformer to get a proper match.

73 & good luck,

Roger (K8RI)



On 2/10/2015 12:55 AM, Jim Thomson wrote:
> 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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