Re: [amsat-bb] Myers' BBQ Grill

[Bob Nielsen <nielsen@xxxxxx>]

On Sat, May 12, 2001 at 10:43:36AM -0500, Bill Howell wrote:
> Hilton wrote:
> 
> >Iam trying to resolve a "deaf" 2.4G downconverter system.   Everything
> >seems to point to an Antenna problem.  My question is, what is the design
> >of the dipole, should there be an indicated short circuit at the coax
> >connector?
> >Thanks
> 
> 
> Hilton... Mine reads zero ohms (DC), too. I checked a similar 
> "dipole", on a Lance MMDS antenna..
> It measures the same.
> 
> Odd. I'm confused. I thought it was a regular dipole inside the 
> weatherproofing.
> 
> Has anyone ripped one of these apart to see what the secret is?

While I haven't actually looked inside one of these feeds, it is quite
common at microwave frequencies to use a balun structure consisting of
a quarter-wave section of transmission line having a short at one end
which transforms to an open 1/4 wavelength away.  There are a number of
examples shown on Page 31-23 of the Antenna Engineering Handbook
(Jasik, ed.), as well as many other antenna texts.

73, Bob

-- 
Bob Nielsen, N7XY                          nielsen@oz.net
Bainbridge Island, WA                      http://www.oz.net/~nielsen
IOTA NA-065, USI WA-028S 
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org