[amsat-bb] Advice on antennas for working the LEO's

[John Kopala]

Hi Gary,

I just thought I'd throw in my 2 cents.  I don't have a great deal of 
experience with satellites, but I will offer a few comments based upon my 
limited experience.

The antenna by Tonna with 13 DBi on 2 and 16 DBi on 70 is going to have a 
fairly narrow beamwidth and is obviously a fairly long antenna.  It will 
need to be pointed with reasonable accuracy.  If you are 30 degrees off you 
might as well be pointed the other way.  With that much gain, you should be 
able to work most satellites without the preamps.  The problem is aiming the 
antennas.  I recommend using azimuth and elevation rotors.  Azimuth alone 
won't do it with narrow beamwidth antennas if the satellite pass reaches a 
significant elevation.  The software programs will tell you where to aim the 
antenna and you can easily do that with the rotor control boxes while 
working stations on the radio.  The adjustments are easy and don't take that 
much time away from operating.

I tried an experiment with a tripod and a set of KLM antennas mounted on a 
cross boom.  Aiming a large set of antennas manually can quickly turn into a 
full time job.  I was testing this to see if it was practical to take to 
scout outings.

After trying the tripod setup, I modified the setup and put in my rotors. 
Using the rotor controllers, made this very workable.  I'll send you a 
picture separately of the setup.  Basically, I had a stake in the ground, a 
5 ft mast slipped over the stake with a rotor at the top end.  The rotor is 
guyed with 3 additional stakes.  Above the rotor is another 5 ft mast 
section, elevation rotor, crossboom, and VHF and UHF satellite antennas. 
Obviously, if you are using a single dual band antenna, the whole setup is 
somewhat simpler.  What you see in the picture is destined for my roof plus 
additional antennas.

If you use an antenna that is small enough to hold and point by hand, you 
will lose a lot of gain vs the big antenna, but it will be a lot easier to 
point.  You still need real time data for the azimuth and elevation and some 
sort of azimuth and elevation aids would help.  Some people enjoy working 
satellites with the Arrow antenna.  Personally, I have not have a lot of 
luck with reading azimuth and elevation, manually aiming, talking on the 
radio all at the same time.

John Kopala
N7JK


Date: Wed, 21 Feb 2007 09:44:00 +0000
From: Gary McKelvie <garym at garym.org.uk>
Subject: [amsat-bb]  Advice on antennas for working the LEO's
To: amsat-bb at amsat.org
Message-ID: <6.2.3.4.2.20070221092821.023911f8 at mail.btinternet.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

Hi to the List,

My names Gary,  I'm just getting started in the sats, initially
looking to work the LEO's with FO 29 in particular.
The station is going to consist of a Yaesu FT 847 cat controlled by
Ham Radio Delux to control the radio for Doppler.

It's suitable antennas that I have a problem with from web pages etc
a lot of people seem to use the arrow antenna,
which unfortunately as far as I can see is not available here in the UK.
There is an antenna by Tonna which is a 9 element on 2 and 19 element
on 70 claimed gain is 13 dBi on 2 16 dBi on 70.
The feed line I will be using to get to the antenna will be a short
run of West Flex 103 (which is half the loss of RG 213)
I'm hoping to avoid the use of pre amps if possible as getting power
to them is a problem.
This antenna set up will be temporary in nature, with it being set up
each time it is in use.
I will be able to rotate the antenna in azimuth by hand or using a
azimuth rotator.
So would this setup work?
So really all I'm not sure is how effective this setup will be and am
looking for ideas and suggestions.

Regards

Gary G7USC



Gary McKelvie
G7USC
Web : www.garym.org.uk