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Re: Phasing CP (was:Re: A question about 75 Ohmconnectors)



on 2/13/03 11:57 PM, Doug Faunt N6TQS +1-510-655-8604 at faunt@panix.com
wrote:

> Yes, you've described it so I understand it.  However, I think I can
> adjust the gamma match of the Arrow driven elements to produce 100
> ohms at each feedpoint (I've not done this yet).  Then all I need is
> one piece of 100 ohm coax (actually 93 ohm RG-62 is close enough) 1/4
> wave long for the phasing line.  The 100 ohm phasing line will join
> the 50 ohm feedline at a tee at the second gamma match.

That would work.  The only thing I can think of that may be an issue is
whether or not that 100 Ohm point on the gamma match is purely resistive.
If it has some reactive component to it, then you still won't get the
correct match.  Still, it's a good idea to try....
> 
> Since I don't have an easy way of determining 100 ohm impedance at
> 70cm, I think I can come close by connecting a 100 ohm resistor across
> each feedpoint, and adjusting for 1:1 SWR, since I do have a 50 ohm
> SWR meter good at 70cm.

Yeah, that works.  I've seen that sort of thing done before.  If you have an
MFJ259B or have access to one, that would give you a pretty good idea of the
impedance of the antenna as you adjust it.

> 
> So, have I missed something?

Not that I can think of with the exception I noted above.  It might not be
an issue.

73,

Jon
NA9D

-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Citizen of the People's Democratic Republik of Illinois

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

http://www.qsl.net/na9d   <- Updated on 1/22/03!!!

"A life lived in fear is a life half lived."


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