[amsat-bb] Re: Antenna advice

Edward Cole kl7uw at acsalaska.net
Sat Jan 5 11:52:36 PST 2008

Roger what Roger said (sorry for the pun ;-)):

But if you are eventually thinking of operating MEO or HEO satellites 
then progressing to high(er) gain antennas, circular polarity, az-el 
tracking, auto-tracking or auto-tuning makes some sense.  This is 
often a financial question so if you are wanting to maximize your 
satellite station for the future then it may make sense to upgrade to 
a larger antenna system.  OTOH if you want to keep expenses low then 
use of omni antennas or a fixed-elevation small yagi with an azimuth 
rotator can be quite usable for the existing Leos and ISS.  For P3E 
and Eagle one will need more (like AO-13/AO-40).

I worked ISS with 50w and a ARX-270 (9-dBd) vertical when ISS was 
1500 km away on our southern horizon.  This antenna is not optimum 
for higher elevation passes of satellites, and a 2m 1/4 WL ground 
plane is better, overall.  I used one with a 432-MHz preamp to copy 
AO-51 Telemetry.

My "AO-40 Satellite Antenna" system is still in the process of set up 
on a new 10-foot tower.  When done it will consist of KLM-22C, 
M2-436CP42, 33-inch offset-feed dish, and 2.4 GHz 
corner-reflector.  145 and 435 will have switchable CP.  The B5400 
az-el rotator will utilize a Unitrac-2000 for auto-tracking and I 
will add auto-tuning on the FT-847.  A 1268 MHz 45-element loop-yagi 
will round out the satellite suite.

But I did not start out with these antennas in 1985.  My station was 
a CC 10T (later a 20T) and a CC 416T with a manual rotation system 
(grab the mast and twist or grab the cord and pull to lift the array 
- cross-boom strapped to a door hinge with cord run thru a 
pulley.  Elevation was established with a series of nails in the wall 
of the building that the mast was mounted on (pull the cord and hook 
it on lower nail for higher elevation).  Station ran IC-211 (10w) and 
MM432 (4w) with Commodore-64 satellite predicts (Oscar locator before 
that).  I worked a lot of AO-10 with that set up...oh and the station 
was set up in a tent in the Alaska bush with a battery for power!

Those were the days,my friend!
73 Ed - KL7UW (back then I was K8MWA/KL7)

At 10:12 AM 1/5/2008, Roger Kolakowski wrote:
>Hi Ken...
>Of course there are advantages to az/el tracking. With "spot on" TRACKING
>you will have better signal levels to work with on receive and be able to
>use less power on transmit.
>The disadvantages of az/el are that you do need ACCURATE TRACKING or you can
>possibly worsen your received signal strength from the Sats. ISS is
>especially a challenge as it is so close to the Earth's surface (~200) miles
>that it's passes can move across your visible sky really quickly.
>Your initial inquiry included a "hands off" requirement. That means tracking
>software that controls the rotors automatically. While you are at it you
>might as well adjust for doppler. Not much on 2 meters but enough, and a
>requirement on 435.
>So...your decision becomes...do you stop operating as you collect this
>gear,software and fund this transition, or do you take the next step up and
>set up an AZ rotor while you are contemplating the rest. How much time do
>you have to accomplish this setup? How much money? What type of antennas are
>you considering? Circular polarization? Antenna gain vs required accuracy?
>You have mentioned ISS several times...it can be worked with a HT and a
>rubber duck...at least on a clear pass. It has been shown many times that
>one of the best antennas for ISS is a 19" whip over a good groundplane. The
>same antenna works on 435 also.
>Your available time and money should help set your goals for your antenna
>system and reap the rewards you are satisfied with.
>Me...I'm a minimalist  ;-)
>----- Original Message -----
>From: "Ken Owen" <n6kth at n6kth.com>
>To: <amsat-bb at amsat.org>
>Sent: Saturday, January 05, 2008 11:20 AM
>Subject: [amsat-bb] Re: Antenna advice
> >
> > Hi folks:
> >
> > So, I understand those that say it's not worth "chasing the last 2
> > with an elevation rotor.  Is there ANY advantage to having EL capability
> > satellite purposes?  What about for working the ISS?
> >
> > Thanks,
> >
> > Ken, N6KTH
> >
> >
> >
> > _______________________________________________
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Ed - KL7UW
  BP40IQ   50-MHz - 10-GHz   www.kl7uw.com
144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w
DUBUS Magazine USA Rep dubususa at hotmail.com

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