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 <[email protected]> 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 > > _________________ > > Topband Reflector Archives - http://www.contesting.com/_topband > > > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > _________________ Topband Reflector Archives - http://www.contesting.com/_topband
