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Re: s-band antenna for LEO work and CAL130215



Bruce,

At 10:36 AM 9/18/2005 -0300, Bruce Robertson wrote:
**snip**
>In order to build an antenna for this unit, I bought a panel plug,
N-connector
>male. It has a teflon post that protrudes about 1/2": this should count as
part
>of any antenna design, shouldn't it? Helix and patch antenna designs seem to
>want the centre connector to be almost flush, so I assume that if I were
to make
>one of these, I'd need to cut down the post.

The height of the connector will add to the length of the helix but helix
antennas are pretty forgiving antennas as far as adhering to exact
dimentions as long as you try.  Hams working at microwave often cut excess
lead and insulation off sma-type connectors to fit projects, so I see no
problem removing the insulation flush with the surface of the sheet metal
reflector of a helix.  My 2.4-GHz helix has copper strap soldered as a
tuning strip line at the connector end of the helix and I drilled a hole
for the N-connector pin and set the strap as close to the surface as I
could without shorting out the strap (est. about 3/32-inch or so).

I thought I could instead build a
>waveguide-in-a-tin-can antenna, subtracting the height of the post in
order to
>determine the proper height of the antenna element.
 
Yep a cylindrical waveguide horn will provide about the same gain as a
5-turn helix; add wire of suitable diameter to extend the coax probe into
the can.  Length about 1/4 or less wavelength (check articles from mw
sources for exact lengths).  The probe is called a monopole.  Distance of
the connector-probe in front of the bottom of the "can" is set for good SWR
and again consult mw articles on this (generically this is about 1/4
wavelength).  The cylindrical horn "can" should be about 1 wavelength long
and 0.7 wavelength diameter for good performance.

>I bought the N-connector panel plug from Surplus Sales of Nebraska, having
been
>unable to find a similar device in Canada. Does anyone have a source for
panel
>plugs that fit flush so that I can work on a panel or helix antenna design?

Have you tried Radio Shack?
GL,
 
73's,
Ed - KL7UW 
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BP40iq,  Nikiski, AK      http://www.qsl.net/al7eb
Amsat #3212
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