Hi Rick, Wes,
I said it was a "killer piece of copper". I did not compare it to anything.
Mostly I like the way that edge-wound coil looks (what was on my mind when
I said "killer") The same way I like a lit up and glowing red 3-1000Z
putting out 1500 watts, or the spooky glow of 866A's and 872A's back in the
day. That's three "killer" tubes :>))
I have some vague recollection of the current on thick, flat conductors
having non-uniform tendencies giving it some non-intuitive aspects. If I
was going to have to do something careful, I'd have to so some digging to
see what that was all about. What both of you proffer seems familiar,
though from subsequent posts is in varying dispute when you get down to the
nits in the issue.
Since you bring it up, the edge-wound coil certainly does dissipate more
heat, and it's sometimes needed. Not all antenna problems can be handled
well by a given tuner configuration. And for the unfortunate antenna/tuner
combination where physics reduces the possible tuner efficiency by putting
heavy current through the coil, it's nice to know the silly coil won't burn
or melt it's supports.
I've certainly done the latter with the coil stock back in the early days
when I still had hair and didn't understand the high RF currents sometimes
involved in TX tuning circuits. The circular shape of the wire in coil
stock wasn't enough counter-influence to keep it from heating the
polystyrene support rods past melting.
The one that is still funny in my recollection (though not at the time),
was done running only 750 watts out (old rules 1000 watts input on CW) on
80m. The droop on that, before it started shorting and got my attention,
was spectacular, and I also made the mistake of touching the melted
polystyrene.
It was an open vertical breadboard matching network connected to 40 feet of
RG-17 that was connected at the other end directly to two ground radials
and an end-fed 133 foot wire. The coil stock was mounted horizontally and
only at the ends. I don't remember what the circuit was at this point, but
in the end it was clear the happenstance 1/4 wave transformation from the
RG-17 set up some considerable RF current in the coil stock. Thereafter the
coil had a "smile" in it.
Thus far I have not managed to melt or burn up my ATR-30 which uses the
aforementioned "killer coil". :>))
73 folks,
Guy K2AV
On Thu, Aug 30, 2018 at 10:34 PM Wes Stewart <wes_n7ws@triconet.org> wrote:
> I agree with Rick. The advantage to the edge-wound inductor is the better
> heat
> dissipation; needed because the Q is lower :-)
>
> Wes N7WS
>
> On 8/30/2018 5:44 PM, Richard (Rick) Karlquist wrote:
> >
> >
> > On 8/30/2018 3:44 PM, Guy Olinger K2AV wrote:
> >
> >> You can also get the edge-wound (flat) 1/4 inch by 1/16 inch coil that
> they
> >> use in the ATR-30 rotary coil tuner. That's a killer piece of copper.
> >>
> >
> > Actually no. Edge wound is inferior in terms of Q to round wire.
> > It only makes sense for a rotary coil, where it needs to be edge
> > wound for mechanical reasons. On a flat strip, the current
> > crowds to the two edges for the same reasons that cause skin
> > effect, thereby wasting most of the copper. Round wires are
> > immune from this because they have no edges.
> >
> > 73
> > Rick N6RK
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> >
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