In a message dated 96-08-23 14:23:59 EDT, you write:
>
>Your 180 degree delay line on 40 becomes about 90 degrees on 80...
>Your 3/4 wave spacing on 40 becomes 3/8 wave spacing on 80...
If you invert the phase of one element via a phase reversing choke a delay
line becomes the correct length for all frequencies below 1/4 wl spacing. The
null will remain in the same direction without a delay line change. The line
should electrically equal (or be slightly shorter if you want to maximize
gain and offset the rear null) than the element spacing.
The only problem that remains is keeping the phasing line flat and the
elements
correctly matched for proper distribution of current. This system increases
BW of any phasing system.
73 Tom
>From jdowning@intelenet.net (John Downing) Sat Aug 24 01:59:34 1996
From: jdowning@intelenet.net (John Downing) (John Downing)
Subject: 40/80 Phased verticals
Message-ID: <01BB911C.DC93B4C0@downing-1.intelenet.net>
Hy-Gain did some great work on phasing two and three multiband verticals
with the 18HT Hi Tower and published a report which is available for the
asking. It's excellent and will give you some good ideas with your H2V.
At V31DX we have used phased H2Vs on 80 for several years in the CQWW
and ARRL DX contests to great effect - I don't think anyone missed our
signal!
Our arrangement is like this: Two H2V verticals spaced one quarter
wavelength apart (in air or about 65' or so) both mounted on a beached steel
barge (now you know the secret) on a north-south axis. The northern H2V has
the 160 meter kit and a tophat, the southern one doesn't. Feed line was random
length (about 200') of RG-213 feeding a coax T. The coax T in turn fed a one
quarter wavelength (thru the coax - use the velocity factor) length of RG-11
(72 ohm)
to the southern H2V and a one half (again, thru the coax - use the velocity
factor)
length of RG-11 to the northern H2V. This was tunable on 80 (SWR 2:1 points
are
100khz apart) and 160 (SWR 2:1 points are typical H2V or about 10khz apart).
We never matched 40 - the resonance point was below the band no matter
what we did. It's very handy - some would say necessary - to have a MFJ SWR
meter to tune the thing.
We found about a 3 db gain over a single H2V on 80 and about a 25 db front to
side over
a single H2V. The quarter wavelength spacing giving a cardioid pattern was
just like
the textbook. A separate set of H2Vs for 40 compared very favorably with our
Cushcraft 2 element 40 beam at 80 feet! We "rotate" our phased array by simply
running out and disconnecting the rear vertical and living with the RG-213 /
RG-11
impedance mismatch - just as we do on 160.
cheers,
John Downing
V31DX / N6YRU (for the next month!)
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