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From: briansalt@NScix.co.uk (B. W. Salt.)
Subject: Re: Antenna question
Date: Wed, 13 Nov 2002 17:06 +0000 (GMT Standard Time)
Organization: Nextra UK
NNTP-Posting-Date: Wed, 13 Nov 2002 17:06:35 +0000 (UTC)
You'll need two lengths of 75 ohm coax, one from each aerial, joined
together at the feeder end; centre-to-centre and screen-to-screen.
To the same point you need a length of 50 ohm coax, length to be 1/4
wavelength multiplied by the velocity factor of the coax used (0.66 for
solid dielectric; 0.86 for semi-air-spaced dielectric).
To the end of the 50 ohm coax, connect the downlead of 75 ohms.
The length of 50 ohm forms a matching transformer between the parallel
75 ohms and the single 75 ohm downlead.
Completely seal the joints!
Remove NS from address before replying.
In article ,
email@example.com (Dave Fenner) wrote:
> How are those side by side pair UHF yaggi array TV aerials
> I have two separate identical TV antennas in my roof, facing
> different directions. Each has own downlead. Now I would like to
> re-mount them to increase gain from one direction. How are the
> commercial pairs connected? Do I change connection at the top or
> can I do something with the downleads at the bottom end?
> I can see one way is a 3 coil transformer. Is there a simple trick
> like the way you can make a balun by looping the inner wire somehow?
> I just want to end up with a standard 70 ohm single co-ax connection
> with a bit more signal. TIA.
> Dave Fenner
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