[TowerTalk] Grey PVC Loading Coil
jimlux at earthlink.net
Wed Dec 6 10:50:28 EST 2006
At 07:05 AM 12/6/2006, Michael Tope wrote:
>----- Original Message -----
>From: "Dan Zimmerman N3OX" <n3ox at n3ox.net>
>To: <towertalk at contesting.com>
>Sent: Tuesday, December 05, 2006 2:43 PM
>Subject: Re: [TowerTalk] Grey PVC Loading Coil
> > "And 14.3 watts more than I can radiate on 160m"
> > Yeah, if I find I can *hear* anything on 160 with this thing, I'll
> > pursue more efficient loading schemes so I don't lose so much in the
> > ground.
> > Dan
>Puts some top loading wires on the vertical and you
>should be able to nearly double the radiation resistance.
>This will reduce the base current and hence the ground
>losses and coil losses. It will also reduce the amount
>of inductance needed, so peak voltage across the coil
>will be reduced. I've run a 45' vertical with a combination
>of top hat wires and center inductive loading on 160
>with very good results. Radiation resistance is about
>6 ohms. With a good ground system efficiency seems
>to be very good (parking it on a salt flat doesn't hurt
>73, Mike W4EF............................
>I use black PVC as coil forms at 1200 watts on 160
>with no problems.
Black PVC, or is it ABS DWV (drain, waste, vent), which is actually a
foam core, and even lower effective dielectric constant. Although,
being black, and pigmented with carbon, and foam cored, it makes a
terrible insulator for HV use, particularly in electrostatic
machines. But at the voltages you're likely to see in an antenna
system, it should be fine. But in something like a Van deGraaff
generator with a few microamps at 500 kV, it is horrible.
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