Topband: 75 meter 1/4 wave vertical on160
4cx250b at miamioh.edu
Sat Nov 17 12:46:17 EST 2018
Hi Doug, I've got exactly the same setup. I use two coils, a 2uH shunt
coil, one side of which is grounded, and a 22uH loading coil that
connects to the top of the shunt coil at the bottom of the antenna.
You drive the antenna where the two coils intersect. Realistically,
you'll probably have to tweak the coil settings bit to minimize the
SWR and to bring the resonance where you want it.
My vertical resonates at 3.530 MHz and 1.815MHz, with a 1.1 VSWR on
160 and a 1.45 on 80.
I use a toroid for the loading coil to make it compact. It consists of
two 2.25" cores T42 material wrapped with fiberglass tape and wound
with RG-316U , with the shield and braid soldered together. It all
fits in a weatherproof NEMA enclosure. I'll send a photo separately.
Sent from my iPhone.
> On Nov 17, 2018, at 10:04 AM, doug dietz <doug49707 at gmail.com> wrote:
> I have been lurking in the background for over a year there have been some
> excellent learning possibilities.
> Thank you all. now on to my question.
> I have a 1/4 wave vertical (about 66 feet) for 75-80 meters I would like
> to try and make it resonate on 1.825. If I put the analyzer on it I don't
> understand the reading.....I know the swr is bad on 160 because the
> kpa-1500 will not match it. If possible I would like to add a coil at the
> bottom with a relay to switch in and out. Any ideas length of wire,
> diameter, of coil, and size of wire, for 1500 watts I am not worried
> about receive only transmit.
> Doug WD8Z
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