# RE: 2.4 ghz antenna

```Hello Jesse

The ARRL Antenna Handbook (18th edition) on page 18-14 & 18-15 shows a
coffee can horn feed for a 4' dish.

It shows the probe at 0.25 * lambda[g] inches from the closed end.

lambda[g]{INCHES!}=11802.85/(sqrt(f0^2-fc^2))

where f0 is the operating frequency [in MHz], fc is the TE11 mode circular
waveguide cutoff frequency [in MHz]

fc[TE11]=6917.26/d [fc in MHz, d in INCHES]

where d is the inside diameter.

I hope I copied that down right. This is assuming you're in circular
waveguide mode TE11, with the length of the can 2 to 3 wavelengths and the
inside diameter 3.39-3.91 inches at 2304MHz.

The Satellite Handbook on the other hand on page 10-22 assumes a horn where
d is about 3/4 wavelength, the length between 1 and 1.5 wavelengths and the
distance from closed end to probe 3/8 wavelength.

Being far too young to have ever seen a 1lb coffee can, I can't quite
picture the size you're talking about... ;-)

73 Howard G6LVB

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Jesse Morris
Sent: 25 January 2001 13:45
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] 2.4 ghz antenna

Good Morning to all,

Can someone in tahe group tell me where to put the quarter wave probe in
a 1 pound coffee can and approximately how much gain it should have (yes
I really do have a 1 pound coffee can)?

Thanks,

73 de Jess - W4MVB
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