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Re: Cheap Yagi Antennas for VHF/UHF: experiences?





>Fred,
>
>Quick question on the "cheap yagi", when you put the next set of elements 
>on
>the
>yagi, did you uses the 6.5 inch offset recommended?

Yes.  Alternatively you can mount both sets in the same plane and use a 
phasing line, but more care needs to be taken to get good circularity.  
Therefore I recommend the 6.5 in spacing version.  If you look carefully at 
the linear antenna picture you'll see that the boom extends 7" beyone the 
last element in the front of the antenna.

>Going through the
>spacings
>listed for the elements on the 435 MHz yagi, if using the 6.5 offset,
>directors
>D3 (yagi 1) and D4 (yagi 2)are at same 'location' on the boom, as are
>directors
>D4 (yagi 1) and D5 (yagi 5).
>From the spacings given, the difference between directors D3 and D4, and
>directors
>D4 and D5 is 6.5 inches.
>How did you handle this, just slightly offset these directors, or did you
>use a slightly
>different offset from one antenna to another? From the numbers, an eight or
>quarter inch offset would only be a few degrees.

At 435 Mhz, this makes almost no difference.  Yes, two sets of elements 
"bump" into each other.  I just mounted the two as close as possible to each 
other as I could (maybe 1/16"-1/8" difference) and
called it good.  If you are concerned, you can bend the ends of the elements 
so the spacing at the ends are exact, and thats about as good as it gets 
anyway.

Good Luck.

Fred W0FMS

>From: Frederick M. Spinner <fspinner@hotmail.com>
>To: <avollhar@physik.unizh.ch>; <amsat-bb@AMSAT.Org>
>Sent: Friday, February 15, 2002 9:44 AM
>Subject: Re: [amsat-bb] Cheap Yagi Antennas for VHF/UHF: experiences?
>
>
> > This is the antenna I used (in linear form) for my uplink in AO-40.
> > Worked FB with a short cable run and 25-50W out of my FT-847.
> >
> > I put another set of elements crossed on it and intend to use that 
>antenna
> > in a CP phased array when spring comes and I can work on my antennas 
>again
> > w/o freezing.
> >
> > Here is a picture (of the linear "cheap yagi"):
> > http://www.mainplant.com/fspinner/W0FMS/rubeao40.html
> >
> > Fred W0FMS


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