[amsat-bb] 2.4 GHz Feed copied from the Mars Viking Lander

["Pieter Ibelings" <elpieter@xxxxxxxxxxx>]

Jerry,

The quad array looks good. I'm sorry to hear that it is not performing well
yet. I am sure you'll get it working good. I am going to build my antenna to
allow adjustment of the separation. Right now I am working on the phasing
harness. It's turning out to be relatively hard to keep the phasing perfect.
I plan on keeping the cables and split within 3 degrees at 2401.

On another tangent:

I recently visited the Air and Space museum in Washington. I took all of my
camera equipment with me. I focused on taking as many pictures of antennas
as I could hoping that I could reproduce some of them for 2400 MHz. One of
the most interesting ones was the antenna on the Mars Viking lander. This
antenna is about 1 meter in diameter and uses a helical feed. They use
something similar to my copper tape method and use a reflector like Jerry is
testing. I took a hi-res scan of the negative and here is the picture:

http://www.ozoni.com/n4ip/viking.jpg

I took the picture at an angle that allows measurements to be made. The
exact diameter of the dish is available on the internet. I plan on getting
this info for you.

I believe the helix is wound on a Bakelite or fiberglass form with about 1.1
inch diameter. That would make the reflector about 2.5 inches. I was trying
to get as close to the antenna and everyone was looking at me funny. It
helps to be 6'7" to be able to get over the plexi-glass protector.
73's

Pieter Ibelings
N4IP

Here's a picture of the whole spacecraft:
http://mars.jpl.nasa.gov/mgs/target/viking.gif


Check out these papers on antenna links with spacecraft.

http://arnaud.labouebe.free.fr/Satellite.html

http://deepspace.jpl.nasa.gov/advmiss/sdsmt.pdf
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