Re: [amsat-bb] S-Band Antenna Comparisons, etc.

[Joseph V Murray <k0vty@xxxxxxxx>]

Hi Dave

I have found if you are working  with dish antennas it is a  good
investment  to have two pieces of square aluminum tube.     Making a
cross shaped jig out of the two square tubes fastened perpendicular,  one
can place one tube across the dish face and have a method to line up dish
pointing , reference for measuring the height of the dish ( used to
determine F/D ration of the dish )  and centering of the focal point and
feed antenna on the dish .   Trying to make sure that a feed antenna is
indeed pointing at the center of the dish with a good axial alignment
from a focal point that is also centered in the middle of the dish is
difficult without a jig.   A buck and a half angle gauge resting on the
square axial tube will measure elevation angle very nicely.   

Have fun

Joe  K0VTY  
========================
On Mon, 08 Jan 2001 19:06:56 -0500 David Reinhart
<wa6ilt@BellAtlantic.net> writes:
>A few years back there was an article in the AMSAT Journal about using 
>a device
>called a "smart level" for accurate pointing of antennas.  The widget 
>is a
>hardware store device that gives a machine-readable output of angle.  
>I don't
>remember if it was analog or digital.  Now that we're faced with more 
>accurate
>pointing requirements it looks like time to dig through the back 
>issues.
>
>Dave Reinhart
>
>"Edward R. Cole" wrote:
>
>> >From: K5OE@aol.com
>> >My comments about the sharpness of the pattern though, are quite 
>serious:
>> >half the gain of this large antenna is lost if accurate tracking is 
>not
>> >maintained within a few degrees.  I've never aimed a dish like this 
>at a
>> >satellite before and I was surprised by how sensitive the pointing 
>is--this
>> >is not like waving your Arrow Antenna at AO-27!
>> >73,
>> >Jerry, K5OE
>>
>> Wait till you try tracking at 10 GHz with >35 dBi gain!!!  That is a 
>beam
>> width of ~3-4 degrees!
>>
>> I'm not sure that ordinary antenna rotators will be accurate or have 
>fine
>> enough movement for microwave operation.  My 2m eme array has 19 dBi 
>gain
>> and the Ham-III rotator is controlled with a HB speed control to 
>slow down
>> movement.  Otherwise I can get only +/- 5 degree positioning!  
>Elevation is
>> easy since I am using a satellite actuator-motor.
>>
>> Ed
>>
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>
>----
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