[amsat-bb] Re: Advice on antennas for working the LEO's (Gary McKelvie)

[John Kopala]

Gary,

My XYL is not fond of my antennas either.  But we are also redoing the 
kitchen with new appliances, new counter top, and having the cabinets 
refinished with new doors.  Then there is the upcoming vacation to 
Greece....  Not sure if that gives any leverage, but it certainly doesn't 
hurt.  I'll still hear plenty about how ugly the antennas are after they go 
up.  The problem is that beauty is in the eyes of the beholder.  A Ham and 
the XYL certainly have different perceptions of beauty.

I have interfaced a TAPR TrakBox kit that I "inherited" to my rotors.  So I 
will have that part pretty well automated.  There are a fairly significant 
number of interfaces that can be used with computer software to track 
satellites.  Take a look at Nova for windows on the AMSAT site.  There is a 
list of the different interfaces that it is compatible with.  Makes a good 
research and shopping list if you plan to go that way.

As far as the ERP goes, does the FT-847 allow you to smoothly control the 
power output?  I have been experimenting using an IC-706MKII-G and a Yaesu 
Mobile FM radio.  The Mobile radio radio has the disadvantage of only having 
high and low power so it is less than ideal for satellite work but it does 
provide duplex FM operation.  You are still working on the antenna setup and 
an automated interface.  In my case, I still need to get the radio to 
complete the setup.  That will wait until I finish the antenna installation. 
I am planning on using an Icom IC-910H.  I believe  its power output is 
continuously variable.  I"m also planning to use the matching preamps for 
weak signals.

The beams with their inherent gain will enable working satellites on more 
passes and lower elevations.  You may experience some fading with fixed 
polarization, but the gain of the antennas may compensate for that.  Some of 
the satellites do require a little more power to get into, but your setup 
should be more than adequate.

Toff; HS0NNU has some good alternatives.  I'm sure you have already read his 
posting.  A friend of mine suggested a similar approach for working without 
an elevation rotor.  Most satellite passes don't reach particularly high 
elevations.  Since you already have an elevation rotor, I would take 
advantage of that.  You can track the satellite for the entire pass without 
having to switch antennas when the satellite elevation is high.

That about covers everything that I can think of.  Sounds like you'll have a 
really good setup when you finish.

John Kopala
N7JK

Date: Thu, 22 Feb 2007 00:23:48 +0000
From: Gary McKelvie <garym at garym.org.uk>
Subject: [amsat-bb] Re: Advice on antennas for working the LEO's
To: amsat-bb at amsat.org
Message-ID: <6.2.3.4.2.20070221234551.023d58c0 at mail.btinternet.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

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 Arrow.
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