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Re: Re:Arrow 14 el 70CM RHCP,or what to do waiting for ao40 to show up



   From: "Jeffrey Griffin" <jeffrey.griffin@comcast.net>
   Date: Fri, 22 Aug 2003 01:37:22 -0400

    Reading the Satellite handbook, starting at page 9-6, it shows' two way's
   to do this. One, using 1/2 wavelength of 50-ohm coax, with 1/4 wavelength of
   72-ohm coax. The other, show's 1/4 wavelength of 72-ohm coax, with 3/4
   wavelength of 72-ohm coax. Both taking into account the velocity factor of
   the coax. This should be easy enough to build. Two things' I don't know how
   to take into consideration.

   1.  The Arrow has it's vertical vs. horizontal plane spaced 6MM apart.

This is one of my questions.
The other is exactly where should we be measuring?  Do the Arrow feed
blocks count?  And how best to make the transition from 75 to 50 ohms
cable, and how much of that counts?  I made a new boom, with the
elements shifted 1/4 wave, but could not get the matching right, so
decided just to go with linear on this trip.  

On Ducie, I had the back half of the M2 22 element cross Yagi, but that
was a pain to assemble, and was heavy.  This setup is much lighter,
and quicker to assemble.  But M2 makes a good product.  For T33, etc.,
I'll be very weight limited, and will probably be using a FT817, or
PCR1000 for the downlink RX.  

BTW, in TZ, I had 50 feet of RG213 with field applied PL259's.  On
Ducie, I had 25 feet of the good stuff with the long number, as
assembled by Cable Experts.  I also had, unknowingly, a bunged
reflector element. 

   2.  How to hook up the harness to obtain RHCP.

I think I have this right.

    So two thing's.  I feel the 6mm offset has to be taken into account, and I
   don't know how to do this. Possibly redrilling and moving one plane?  And
   what is better the 1/2 WL 50 ohm and 1/4 WL 72 ohm method, or the 1/4 WL 72
   ohm  3/4 WL 72 ohm. Any ideas?

   73 Jeff kb2m

73, doug

In Aviles, with a cold and probably an inner ear infection.
The EA's are taking care of me.
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