[amsat-bb] Re: CP antenna from 2 WiFi panels
Gary "Joe" Mayfield
gary_mayfield at hotmail.com
Mon Jun 7 19:53:15 PDT 2010
You can place them side by side and introduce the delay in the feed line of
one as well.
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of John Belstner
Sent: Monday, June 07, 2010 9:37 AM
To: Greg D.
Cc: amsat-bb at amsat.org
Subject: [amsat-bb] Re: CP antenna from 2 WiFi panels
These panels are patch style antennas and as such you will not be able to
place one behind the other to obtain circular polarization. Placing one
next to the other will at best produce an elliptically polarized pattern,
and you should use a 50 ohm splitter to keep your impedance 50 ohms. The
shape of the patch and position of the feed point is typically how you
obtain circular polarization with a patch antenna.
Or, you can obtain RHCP with the same or more gain and less trouble by
making a Helix. A sheet of aluminum, #8 copper wire and and a piece of PVC
of the right diameter is all you need.
Or, you can try just a single panel and see how it performs for a while.
73, John W9EN
W9EN at AMSAT.ORG
On Jun 6, 2010, at 1:15 PM, Greg D. wrote:
> Hi folks,
> Before I start nailing stuff together, I just want to verify what I'm
> I want to make a 2.4ghz Right-Hand Circular antenna from two flat panel
Wi-Fi antennas. The idea is to mount them at 90 degrees from each other,
with one 1/4 wavelength in front of the other. Combine the two feeds with a
simple Tee (the feeds are of equal length), and into the pre-amp. Since I'm
not transmitting, I'm not too worried about the resulting 25 ohm impedance
(or should I be?).
> If it matters, the panels are from HyperLink Technologies, their model
HG2414P, with a claimed 14dBi gain.
> So, the questions:
> 1. 1/4 wavelength at 2401 mhz is ((3 x 10**8 / 2401 x 10**6) / 4) meters,
or about 1.23 inches. Right?
> 2. Most of our 2.4 ghz satellite downlinks seem to be either linear or
RHCP, so I'm guessing that RHCP is probably the preferred construction.
> 3. Looking at the Satellite Experimenter's Handbook (figure 7-10), I
believe the panel rotated 90 degrees counter-clockwise as seen from behind
the panels should be the one farther out in front, for RHCP. (Their picture
shows clockwise for LHCP.) Is this correct?
> Greg KO6TH
> The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with
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