[amsat-bb] 435 offset yagi phasing

Andrew Rich vk4tec at people.net.au
Fri Dec 28 03:25:06 PST 2007


I have had good success with just one yagi of an offset crossed array I am


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
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

Andrew Rich VK4TEC

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