[600MRG] Lightweight coil construction

[Pat Hamel]

Dick,

I was thinking of metal rods bolted to a plywood or metal base for a coil 16
inches in diameter. Wood dowels would suffice for smaller coils.

Winding the basket weave requires an open-top as you said, but you need to
stop every turn and do the ties, which is probably why the idea has been
ignored.

The tradeoff is time against weight and losses.

It would be easier to wind a coil on a solid form, but the core of the form
will add losses. 

The paint-soaked ties at the crossovers provide a place to make the
structure rigid without the form.

After the wet season, I will need to try it myself.

73,

Pat W5THT & WD2XSH/6

 

 

 

 

 

  _____  

From: Dick Bingham [mailto:dick.bingham at gmail.com] 
Sent: Friday, January 23, 2015 12:39 AM
To: Pat Hamel
Cc: 600MRG
Subject: Re: [600MRG] Lightweight coil construction

 

Sounds like a great idea BUT I am having a hard time envisioning

how one is going to route 16 * pi * D inches of wire between dowels

without tangling/kinking such a long length of wire unless the top of

each dowel is open.

If the top is open then it would seem that as you dress the wire from

dowel-to-dowel they will begin to pinch inward to make a tapered

coil.

Am I missing something here ?

Dick/w7wkr and xsh-26

 

On Thu, Jan 22, 2015 at 8:12 AM, Pat Hamel <pehamel at cableone.net> wrote:

Some of you may remember that I used a suspended coil made of one layer of
boat-building fiberglass and flat copper tape on 600 meters for many years.
I used weed-eater line to take the weight of the lower part of the antenna.

Building a coil that can be suspended and lighter than mine just jumped out
at me when I was re-reading the first ARRL Handbook (which came with the
regular hardcover handbook I got a few years ago.)
The technique is called basket-weave, and should scale up to 630 meters
easily.

First calculate the ballpark inductance you need and the size of the coil.
The length and diameter should be the same for best "Q".
Mine was 16 inches in diameter and ended up slightly less than 16 inches
long.
Get your insulated wire and some tarred or otherwise UV-resistant tie cord
(net making cord is fine).
Get a board and a bunch of rods or dowels. Drill a circle of holes (an odd
number) on the board to hold the rods or dowels upright.
Fasten one end of the wire and wind wire in-and-out of the rods for two
turns. The wires should cross between rods. Tie them together where they
cross.
Weave your way up the number of turns that you need, tying them as you go.
Remove the dowels and you have a self-supporting, lightweight, low-loss
coil.
Spray paint to match foliage and set the knots, and hang it.
My primary duty as caregiver has kept me from building the 600 meter SSB
exciter, but I still monitor and hope to be back on the air
I hope this helps,
73,
Pat W5THT & WD2XSH/6







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