Coil Construction, was: [AMRadio] Fun with 4D32's...


david knepper collinsradio at adelphia.net
Thu Jan 4 11:49:45 EST 2007


Try Home Depot or Lowes as suggested.  Plexiglass is available locally.

I repaired some of the HDVL with this stuff.


Dave, W3ST
Publisher of the Collins Journal
Secretary to the Collins Radio Association
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----- Original Message ----- 
From: "Larry Keith" <kq4by at rocketmail.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Thursday, January 04, 2007 11:46 AM
Subject: RE: Coil Construction, was: [AMRadio] Fun with 4D32's...


> You can buy approximately 1/8" thick Lexan (or
> polycarbonate) in 8x10 sheets at Lowes or Home Depot..
> I cut it into 3/8" wide strips, using a small bandsaw
> and a fence.  Other dimension Lexan sheets can be
> bought at U.S. Plastics or McMaster-Carr.
>
> I have a stack of already-cut ribs (10" long x 3/8
> wide" that would have to be drilled. If you just want
> a few to play with, verify that your QRZ address is
> good and I will send you some (8 or so?)..
>
> And, I have some factory-punched strips that are good
> for AWG 12 wire, 6 TPI..  I had to pay for those and
> order a 1000 to get them. 8-)  If you want to try
> those, I need to get $10 for 4 strips (10" long x 3/8
> wide x .090 thick). No charge for shipping.
>
> I have forgotten what size wire you were planning to
> use.  I have found that my "process" becomes more
> difficult if I use less than # 12..  I have had good
> results using AWG 8, 10 and 12.  And, you can get that
> wire at The Wireman..  Buss wire, solid copper tinned.
>
> BTW, with 1/8 or so thick stock, a 3/32 drill works
> good for #12, 7/64 will work for #10. I have lost my
> notes for # 8 but I would start with a drill size that
> is slightly larger than the wire diameter. Too large
> will work but too small will bind!
>
> You can stack the ribs together and tape them (I use
> wide masking tape, just about two layers, at each
> end).  Then you drill all the ribs at once..
>
> As you thread the wire through the ribs, wear some
> cotton gloves.  Try to keep the ribs straight and
> evenly-spaced as you do the threading.  I have found
> that if the wire starts to bind a small squirt of
> WD-40 along the rib will help.
>
> After the coil is threaded, position the ribs and run
> a bead of model airplane cement along the rib where
> the wire comes through.  Do a rib, let it dry, then do
> another rib, etc.. until all four are done.  I usually
> do both sides of the ribs to get a "firm" coil.
>
> Let's see: form size is usually 3/8 to 1/2 smaller
> than the desired coil diameter.  I use a 2 5/8 coil
> form made from PVC pipe couplings to produce 3"
> diameter coils.  It is pretty close.
>
> And, I wind the coil with moderate tension by passing
> the wire through a bench vise (padded with a shop
> towel).
>
> Figure out the number of turns and add about 10
> per-cent to allow for expansion.  So, when I wind a 60
> turn coil, I actually wind about 66 turns on the coil
> form.  If you need long coil leads, add a couple of
> turns..  You can always cut off the excess -- it's
> tough to add wire to the coil..  8-)
>
> Hope that helps..
>
> 73,
>
> Larry
> KQ4BY
>
>
> --- Brett gazdzinski
> <brett.gazdzinski at verizonbusiness.com> wrote:
>
>> Larry,
>> Where do you get the strips of plastic to drill
>> and pass the coil through?
>>
>> Brett
>> N2DTS
>>
>> > -----Original Message-----
>> > From: amradio-bounces at mailman.qth.net
>> > [mailto:amradio-bounces at mailman.qth.net] On Behalf
>> Of Larry Keith
>> > Sent: Tuesday, January 02, 2007 1:19 PM
>> > To: 'Discussion of AM Radio in the Amateur
>> Service'
>> > Subject: RE: Coil Construction, was: [AMRadio] Fun
>> with 4D32's...
>> >
>> >
>> >
>> >
>> >
>> > Thanks Larry.
>> > How do you keep the spacing of the holes
>> > exact?
>> >
>> > I have a "homebrew" table that attaches to my
>> small drill
>> > press.  The table
>> > has a fence and a stop.  I use spacers (plywood
>> > strips)stacked against the
>> > stop.  I drill a hole and remove a spacer,
>> reposition the
>> > work, drill a
>> > hole, etc..
>> >
>> >
>> > Since the handbook says the antenna tuner is good
>> > for 250 watts of AM, I would need to at least
>> double
>> > the size of things, from the #14 at 8 tpi, about
>> > a foot or more long, to ?
>> > #10, or #8, or thin copper tubing?
>> >
>> > I have built coils using #12, #10, #8 and using
>> copper
>> > tubing, using the
>> > same construction methods.
>> >
>> >
>> >
>> >
>> > Balance is important, maybe hard to do with
>> > a home brew coil..
>> >
>> > Why?
>> >
>> >
>> >
>> > I did not study the text, not sure if its supposed
>> to
>> > cover 160 meters, but if I built one, might
>> > as well include 160...
>> >
>> > You just doubled the coil size, if it wasn't
>> designed for 160...
>> >
>> >
>> >
>> > I know I will need to make some sort of coil
>> > form/support to achieve a good balance.
>> >
>> > Polycarbonate sheet.. Mounted on stand-off
>> insulators..
>> >
>> >
>> > 73,
>> >
>> > Larry
>> > KQ4BY
>> >
>> >
>> >
>> >
>> >
>>
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>>
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>
>
> Larry Keith
> 231 Shenandoah Trail
> Warner Robins, GA 31088-6289
>  kq4by at rocketmail.com
> larry.keith at yahoo.com
> 478-329-0030
>
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