Topband: Detuning shunt fed towers

[DAVID CUTHBERT]

A UHF connector won't flash over at 1500 watts if the VSWR is low.

Dave WX7G
On Nov 29, 2012 9:04 AM, "John Harden, D.M.D." <jhdmd at bellsouth.net> wrote:

> I have a 100 ft 45G, shunt fed tower with stacked monobanders for 80 -10
> meters. This includes a 24 ft mast with 12 feet out the tower top. I do not
> even worry about detuning it.
> The shunt (4 wire) cage only goes up to 30 feet due to monobanders down to
> about 35 feet. It requires a 2000 pfd vacuum variable in series and a 1000
> pfd vacuum variable to ground (Omega match) to resonate the system. The
> series capacitor is motor driven by a 1 RPM, 12 VDC motor. The SWR remains
> flat over the band measured at the match and in the shack. I have right at
> 40 radials on ground. At this point the curve becomes asymptotic..........
>
> With an Amphenol Type "HN" connector there is never any flashover.
> SO-239's did not cut it. Type "N" is even worse.
>
> My Hi-Z 4-8 PRO RX antenna is over 100 feet away and there appears to be
> little interaction. If you do the math there should be interaction but
> there is so little "real" interaction that I simply disregard it.... The
> guys at Hi-Z will tell you there is very little difference between the 4-8
> PRO and the 8 el array that is in a 200 ft diameter circle. They have both
> up. The decrease in beam width between the two is inconsequential to me....
>
> I can now hear about anything that is on compared to others in my area,
> and can work it quickly if I can hear it. The Hi-Z array is that good....
> The waters of the sea have parted for me on top band.
>
> 73,
>
> John, W4NU
> K4JAG (1959 to 1998)
> ______________________________**_________________
> Topband reflector - topband at contesting.com
>