[amsat-bb] Re: Advice on antennas for working the LEO's
garym at garym.org.uk
Wed Feb 21 16:23:48 PST 2007
Hi John and others,
Thanks for the picture lovely set up. If only I could get the XYL to
let me stick something similar on the roof :)
I do have an elevation rotator already :) IIRC a Kenpro 550 or 450.
I have played about in the past with satellites, at that time I had a
11 element 2 meter RHCP and a 19 element 70 RHCP (Hence the elevation rotator).
I mainly listened rather than transmitted.
So really I have all the equipment except for a way to automate the
antenna control, which as you say isn't too difficult to do manually
and an antenna.
I really don't thing the XYL will let me put up the 11 and 19 element
antennas which I still have, as she thinks I have enough antennas in
the air already <g>
As you can see the sats aren't a passing fad with me, it's just that
I will be on LEO's as a way of compromise. It has taken me a while to
get back to them, but i bought the 847 recently to motivate me to
actually put my words into action rather than just wishing on a star :P
Several people have suggested using a vertical antenna such as a
colinear. I have actually already tried this and the results are very
disappointing, which I put down to my location rather than anything
else as where I am is not particularly that good certainly form a
VHF/UHF point of view.
Other things I was wondering about was the ERP at the satellite,
would it be too high causing me to be an alligator?
Roughly the ERP on 2 would be about 50 watts and higher on 70 as the
gain would be about 13 dBd plus whatever 5 watts equals. losses
should be very small as the run of coax would be less than 30 feet,
most of that being Westflex 103 and just the a very short length of
RG 213 for getting the antenna hooked up and round the rotator/s.
I'm not sure how to work out the path loss from my location (is there
a standard figure or equation to use?)
so at present I'm still very tempted to go with the Tonna, as it
certainly seems to be better than the arrow antennas in that it has a
higher gain figure.
Please note I am not commenting on the quality of the construction of
The other aspect I'm wondering about is cross polarization losses,
the way that I plan to have it configured is with the 2 meter section
horizontal and the 70 cm vertical. So would that be significant for the LEO's?
73 Gary G7USC
At 23:12 21/02/2007, you wrote:
>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
Web : www.garym.org.uk
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So Long and Thanks for all the Fish
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