RE: [amsat-bb] Arrow 14 el. 440 crossed yagi - feeding?

["Howard Long" <howard@xxxxxxxxxxxxxx>]

Hi Mal

> 1.  If I divide the coax and feed one antenna with a 1/4 wave stub and the
> other with a 3/4 wave stub it appears I'd get a 180 degree phase shift.

As long as both driven elements are level with each other on the boom, yes.

> 2.  Although the literature I've found prescribes different coax
impedences
> I wouldn't think the mismatch would be all that significant if I used 52
ohm
> coax for it.

Assuming both DE's present 50 ohms, you will end up with a 25 ohm combined
feedpoint using 50 ohm feeders, or an SWR of 2:1 - rather high. That's not
the only thing to note. When phasing antennas it is much more important to
get the matching right because power will potentially flow
disproportionately into one antenna and not the other, ending up with little
or no benefit from the attempt to make CP. See
http://www.g6lvb.com/images/stacking.gif for why. Using 75 ohm coax will
improve the match and make it much closer to a combined 50 ohm match.

3.  How does one hook it to the driven elements to get RH or LH?

http://www.g6lvb.com/images/rhcp.jpg shows RHCP. The 'hot' ends are the
folded sides of the DE's in this example (actually, it doesn't matter as
long as you are consistent!).

Good luck! I know I spent hours and hours on this myself three or four years
ago.

73 Howard G6LVB


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