[TowerTalk] 1/8 wave spaced 80m verticals

[Jim Lux]

Very nifty...
Short elements minimize the mutual coupling, 50 ohm load resistors also help
swamp the antenna Z, so that, in combination with the combiner (which would
tend to put the reflected power into a load, no?) you're basically making
voltage probes and summing them with delay lines in a classic RAKE receiver.

----- Original Message -----
From: "Richard Karlquist" <richard at karlquist.com>
To: <n4gi at tampabay.rr.com>; <towertalk at contesting.com>
Sent: Wednesday, September 10, 2003 7:40 PM
Subject: RE: [TowerTalk] 1/8 wave spaced 80m verticals


> > > At 01:07 PM 9/10/2003 -0400, Roger D Johnson wrote:
> > > I toyed with the idea of feeding
> > > >the elements in phase for transmit and with the delay for receive.
> > > >It made the system a bit more complicated but resulted in better
> > > >transmit signal while still having the F/B on receive.
> >
>
> Receive only arrays can be fed differently.
>
> Last spring I put up an array of 1/8 wave spaced (32 ft)
> verticals for 80 meters aimed at Europe.  The verticals were
> 30 feet high and fed through 1:1 isolation transformers
> located at the bases.  Four 30 foot radials were used
> for a counterpoise.  The antenna side of each
> transformers had a 50 ohm resistor across it.  An broadband
> electrical delay of 32 nsec was added to each front vertical
> using a lumped element delay line (coax could also be used).
> 32 nsec is how long it takes a radio wave to travel 32 ft.
> The front and rear vertical pairs were combined out of
> phase with a 180 degree hybrid.  The four pairs
> were then combined with a 0 degree hybrid.
>
> This kind of array not only works well across 80 meters, but
> also has excellent F/B on 160 and even in the broadcast band.
> I could listen to a station 1500 miles away on 940
> kHz while rejecting a local on the same frequency
> (they just happened to be in the right directions
> for the array).
>
> Note that the feed technique described above will
> NOT work with full size verticals (ie 65 feet on 80 meters).
> For example, my array stops working on 40 meters
> because the elements are full size there.
>
> Rick N6RK
>
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