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RE: 10m antenna options.



Freeman,
             Regarding 10m antennas. One obvious option is to use the metal 
roof as a reflector for a horizontal loop and adjust the spacing between the 
driven element and the reflector to ensure a 30 degree takeoff for AO-7 in 
mode-A.

Personally, I'd recommend the following for a simple, effective "gain" 
system. (assuming you have at least a "postage stamp" garden).

A 10m Maypole!.

3 x resonant sloping dipoles spaced round a short metal mast, switchable by 
DPDT relays arranged so that the coax inner is also switched, ensuring that 
in each direction of 120 degrees you have 1  director and 2  reflectors.

Using relays, and done properly, the dipole will be resonant and each of the 
reflectors will become 5% longer. Instantly switchable from the shack in 3 
arcs of 120 degree.....(which beats a 60 second turning time for a rotor).

This system's boresight "fires" at 30 degrees elevation (which is where you 
want to be for AO-7).

The dipole can be made from RG-58C/U with the inner conductor and braid 
shorted together at each end (FAT = good). In this case the resonant length 
will be slightkly shorter than the book formula (use a dip meter or SWeaR 
meter).

73 John. <la2qaa@amsat.org> <la2qaa@hotmail.com>
............................................................................

>From: "Freeman P. Pascal IV" <pascal@pascal.org>
>To: amsat-bb <amsat-bb@AMSAT.Org>
>Subject: [amsat-bb] 10m antenna options?
>Date: Mon, 07 Jun 2004 00:04:23 -0600
>
>I'm curious what folks are using for mode-A receive antennas?  I'm using
>my trusty R7, but I expect I could do better.  I hope so anyway, today
>was a bit frustrating working AO-7 when it was in mode-A - I was hearing
>a lot more noise than usual, enough to drown out my own downlink.
>
>I'm thinking of putting up both a 10m turnstile and a horizontal loop.
>
>In the next year or so, I'll be redoing our roof on our home, and I'm
>thinking of using metal roofing (something very popular here in NM).
>How much interaction should I expect between the roof and my 10m
>antennas?  I wouldn't expect too much interaction with the VHF/UHF
>antennas since they would be higher than a wavelength or two above the
>roof.
>
>-Freeman, N5FPP
>
>
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