[Lowfer] a thought on coils

Thu, 14 Feb 2002 19:09:29 -0800

Very true Bill. This would be the hot set-up for someone wanting to loaf in
a residential area or where they are encroached upon by trees. The plus side
is you know longer have to sneak-up on your antenna to tune it. The down
side is all the trips you and/or the coil will take up and down the tower to
get it peaked just right.

73
John/AB4MS/JDH

----- Original Message -----
From: Ashlock,William <[email protected]>
To: <[email protected]>
Sent: Thursday, February 14, 2002 2:32 PM
Subject: RE: [Lowfer] a thought on coils

> John,
>
> Very interesting! I would expect the dual pie windings would do fairly
well
> by themselves and have almost enough inductance without the ferrite core.
> The HV winding on a TV flyback transformer would be similar and is not
> influenced that much by the core. It's possible that Walt used the core
more
> for tuning than to reduce the total number of turns required. There would
> certainly be much less magnetic field intensity in his core compared to a
> core that is wound over its full length. It could also be that Walt used a
> ferrite with a low permeability having a higher saturation value than
> commonly used cores.
>
> I like the idea of placing the loading coil close to the top hat. This
> maximizes the effective length of the antenna and reduces the effect of
the
> stray capacity from the vertical portion to the lossy soil.
>
> Bill
>
> -----Original Message-----
> From: john hoopes [mailto:[email protected]]
> Sent: Thursday, February 14, 2002 2:15 PM
> To: [email protected]
> Subject: RE: [Lowfer] a thought on coils
>
>
> Bill, although I have never personally experimented with ferrite loaded
> coils, I have read various articles with the data claims you mention. It
> seems pretty discouraging at first, and had it not been for my visit to
> Walt's, I would have never given ferrite loaded coils a second thought.
>
> Walt went into some detail about his coil but the only thing I can
remember
> is that the PI windings were jumble wound. That struck me as rather odd,
but
> who am I to argue with success. I know Walt was a stickler for efficiency.
> He told me "If it isn't efficient, I'll rip it out."
>
> From what I can remember, the coil was enclosed in what appeared to be a
4"
> piece of PVC with end caps. Total length seemed to be 4" or so but it was
> hard to tell because the coil was mounted at the top of his antenna just
> underneath the top hat. I must admit I was a little disappointed at first
> because I expected to see a huge coil at the base of his tower. Instead
> there was a small aluminum box that housed a matching network from the
> transmitter to the low Z of the antenna.
>
> BTW, Walt used a home brew transceiver for both transmitting and receiving
> that was a beautiful piece of work. It is too bad that Walt is no longer
in
> the hobby because his contributions are truly missed.
>
> 73
> John/AB4MS/JDH
>
>  -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> On Behalf Of Ashlock,William
> Sent: Thursday, February 14, 2002 12:15 PM
> To: '[email protected]'
> Subject: RE: [Lowfer] a thought on coils
>
> Hi John,
>
> >The simplest coil I ever encountered was made by Walt
> >Glazar, W3WI. His beacon WI was heard all over the East coast as well as
> the
> >mid west and it consisted of nothing more than a PVC form with two pi
wound
> >litz sections over a small ferrite rod. Walt was a stickler for
efficiency
> >and if it didn't perform, it didn't stay in his beacon. Ferrite is very
> >useable if you don't saturate it with too much power provides an easy way
> to
> >tune a coil to resonance.
>
> I have spent many hours trying to design loading coils using various types
> of ferrite cores because they appear to offer reduced size and ease in
> construction. The best Q I have been able to obtain is approx 100 at 150ma
> of current. Turns out it is very easy to saturate ferrite cores. I have
seen
> boasts of transmitting performance for these coils from many sources, but
> when it comes to the actual coil Q, at the typical 150ma antenna current,
> there's always a conspicuous lack of data.
>
> Speaking of simple coils, using Litz on a 4" PVC pipe (preferably with
> slots) a Q of >300 is no problem at all. Not sure why the 'bucket brigade'
> approach is so popular, except for the lower cost of the house wire. The
Rac
> for #14 copper wire at 185k is not really that good because of the 'skin
> effect' losses.
>
> BTW: Do have or can you get some more details about WI's loading coil?
>
> Bill
>
>
>
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