[600MRG] Trap-Loaded antennas

Tue Sep 15 17:45:58 CDT 2015

First of all, before I answer your questions below (if I can), I want to share 
with you and the list some of what I consider to be valuable links:

First this one, originally from QEX magazine:

http://www.ik4hdq.net/doc/testi/TrappCoassMulti.pdf

Then, this one which discusses the above in further detail:

http://www.i1wqrlinkradio.com/antype/ch4/chiave1368.htm

And then, there is this one:

http://n6mw.ehpes.com/CT5.pdf

OK. Now on to your questions: I hope I can answer them correctly.

On 15 Sep 2015 at 12:29, dick.bingham wrote:

> I am still in the dark regarding how the wires are connected on either end of
> the "resonator". Is the final end of the top winding left floating?

No,

Although it is not clear from the drawings, you use ONE length of stripped 
RG-58 to make TWO windings. You first wind the bottom winding, "strap" it 
with tape strips, then wind the second winding over the top of the first one, 
then strap that one with tape-strips.

> Is the
> folded-back end of the lower winding connected to the beginning of the top
> winding - it appears to be so.

Well, not exactly: the end of the bottom winding is continued to the top 
winding, so there are ultimately only two ends. The "folded back" end of the 
lower winding continues across the UNDERSIDE of the form to hole #3, then 
continues as the upper layer.

> I have yet to determine from the pix and words
> exactly what is connected to what.
> 
> My best guess is as follows:
> - #1 is start end of inner winding
> - #2 is terminating end of inner winding

Well, yes, except that the numbers, #1 and #2 describe the HOLES, not the 
ENDS of the wires. THAT is what is so confusing about his description.

> - #3 is beginning end of outer winding
> - #4 is terminating end of outer winding

Yes, but see above.

But #2 and #3 are the same piece of wire.

> #1 is poked thru a hole on left side of coil form and extended out to be
> connected to antenna wire on left side of trap.

Yes.

 The remainder of the inner winding wire is wrapped
> along the coil form and poked thru a hole on the right end of the coil-form and
> considered to be the #2 connection.

Well, #2 is not a connection: it is simply a hole in the form.

> The wire continuing on from what we are calling the #2 end

...hole...

 of the inner winding
> is then poked thru the center of the coil-form to a hole close to the hole thru
> which #1 has been inserted to become wire-end #3 after being poked thru this new
> hole to begin the outer winding.

Yes, but the #3 is actually the hole, because the wire simply crosses under 
the top winding to hole #3, then continues as the top winding.

> This wire is wrapped on top of the inner winding along the coil form to the
> right side of the coil-form and poked thru a fourth hole to become wire
> connection #4.

As I said: it is confusing. The numbers are the HOLE numbers, not the WIRE 
numbers.

Out of hole #4, you have the end of the wire which began at hole #1, so you 
end up having only two ends: one out of hole #1 and the other out of hole #4.

The capacitance is then that capacitance between the turns AND between 
layer one and layer two.

This is one reason the author said to use very tight strips of tape to "bind" the 
turns of layer #1 together so that the tight turns of layer #2 won't force the 
turns of layer #1 apart.

> I highly suspect wire-end #4 is connected to an antenna wire to the right side
> of the trap.

Correct.

>The series-connected two windings make a complete electrical
> circuit and the inner/outer winding coupling-capacitance somehow form a
> parallel-coupled LC resonator. For whatever reason, I can not visualize the
> equivalent circuit .

At least one of the links I provide above shows how it works.

> Articles describing winding trifilar connected turns on a toroid core to make a
> doubly balanced mixer are very careful to describe what is connected to what
> which these articles fail to do !

Yes. I totally agree.

> Also, the great care to wrap with tape or apply shrink-fit tubing over the
> resonator seem like a total waste. The inner part of the traps where the wires
> penetrate the coil-form appear not to be protected from moisture. I can envision
> lots of moisture being sucked into the sealed air space under the tape or
> shrink-tube thru those pass-thru holes.

Well, yes, but the reason for the shrink-wrap is to prevent the windings from 
forcing themselves apart. The windings must be very tight to control the 
capacitance.

The insulation will have no holes in it if done correctly, so moisture will not 
effect it.

> A drawing that shows the connections used in these traps is badly needed ! I
> hope the above musings on my part make some sense to you . . .

Yes, of course they do. And I hope my explanation helps. I will try to draw up 
a clearer drawing of how the coils are made and will try, as soon as I can, to 
post that to "our" website;

http://www.600mrg.com

which, so far, has never been used. :-)

So far, it has become fairly clear to me that one may be able to build a 
perfectly usable single antenna which will cover 160 through 10 meters AND 
630 meters in a reasonable amount of space on a normal-sized city lot all fed 
with 50 ohm coax and not requiring an antenna coupler.

But, until I build it, install it, and test it, I won't know.

Ken W7EKB /24