First, why is 393 a requirement? RG142 silver center/double silver
braid is rated 2000w at 50Mhz. I've been using 142 for several years at
QRO in 240-31 wound chokes and not had a problem. Then the big snap-ons
will fit. I use the big box plastic junction boxes, Carlon or Thomas &
Betts. 4x4x4, 6x6x4 and 6x6x6 are large enough depending on the core count.
Ferrite cutting/shaping is done with diamond tools and lots of water
based coolant flushing. I tile saw will cut it. One requirement for
the expected inductance is the surfaces mate precisely, a few microinch
surface roughness. I don't think a tile saw will produce flat enough or
smooth enough mating surfaces. Look at the flatness/finish on the big
clamp-ons, that is what is needed. The gap affect can be measured by
measuring inductance cut/not cut and calculating the equivalent air
gap. I have a $50 Harbor Freight tile saw for cutting fiberglass stock
and tubing - works fine for that, but does make a mess.
A surface grinder with a thin (0.035") diamond saw will make a
satisfactory cut and finish but it is a tedious cut with usually a slow
"plunge cut" automatic downfeed. It is also very very messy and the
grinder owner may reject the job on that basis. Beside very high
hardness, the ferrite particles are very abrasive. In a previous life I
was engaged in ferrite cutting and shaping for recording heads, the
grinders only did that and were totally enclosed. Depending on the
ferrite composition there might be some cobalt or other hazardous trace
elements that are a concern. Perhaps a tower-talkian knows the type 31
composition.
At one time I rebuilt a surface grinder from a WE microwave ferrite
making operation - quite a mess. Another common ferrite grinding
operation was making deflection coil armatures for precision CRT's.
Grant KZ1W
On 2/9/2015 9:55 PM, 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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