[amsat-bb] Re: 435 offset yagi phasing

[SV1BSX]

Andrew,

don't spend your time... your questions are already answered on the
following pages:

http://sv1bsx.50webs.com/antenna-pol/polarization.html


and also here:

http://hjem.get2net.dk/ole_nykjaer/oz2oe/xyagi/build_yagi.html



Happy New Year

73 de Mak, SV1BSX




----- Original Message ----- 
From: "Andrew Rich" <vk4tec at people.net.au>
To: "Amsat-Bb at Amsat. Org" <amsat-bb at amsat.org>
Sent: Friday, December 28, 2007 13:25
Subject: [amsat-bb] 435 offset yagi phasing


> Hi
>
> I have had good success with just one yagi of an offset crossed array I am
> building.
>
> http://wa5vjb.com/yagi-pdf/cheapyagi.pdf
>
> I will add the other elements shortly.
>
> I am not ready to tackle the phasing part.
>
> I hope I have this right.
>
> 1. The yagi's are offset, by 90 degrees so that is the offset already.
> 2. Both yagis's should then have the same length of coax coming from each
> one.
> 3. Both yagi's will require a 1/4 wavelength of 75 ohm coax for each feed.
> 4. Remebering that the velocity factor is 2/3 in coax cable, or the speed
> of
> light 200 instead of 300.
> 5. Both 75 ohm feeds then join at a tee, the result of the 50 ohm antenna
> and 70 ohm feed giving around 120 ohm
> 6. By tee'ing the two together, this should present around 50 ohm,
> required
> for the main feedline.
>
> Does that sound right ?
>
> ( 200/435 MHz ) /4 = 11.49 cm for each feed to the tee junction of 75 ohm
> cable.
>
>
> ----------------------------------------------------------------------------
> Andrew Rich VK4TEC
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