[amsat-bb] Re: Antenna advice
n6kth at n6kth.com
Sat Jan 5 13:35:15 PST 2008
Hi again folks:
Thanks for the great advice. I guess I'm already more than half way to
having a MEO/HEO capable station, so I might as well add the AZ/EL rotor. I
have a FT-847 and I've ordered Gulf Alpha 2 Meter 5x5 Circular Polarized
yagi and a Gulf Alpha 70CM UHF 8x8 Circular Polarized yagi. Since I'm gone
this far, I might as well do it "right" and by a full-service rotor,
interface and software. From reading the posts on here about polarization,
I'm thinking of having Gulf Alpha add polarization switching capability to
the antennas I've ordered, but this would add about $400. Any thoughts?
From: Edward Cole [mailto:kl7uw at acsalaska.net]
Sent: Saturday, January 05, 2008 11:53 AM
To: Roger Kolakowski; Ken Owen; amsat-bb at amsat.org
Subject: Re: [amsat-bb] Re: Antenna advice
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
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:
>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
>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)
>that it's passes can move across your visible sky really quickly.
>Your initial inquiry included a "hands off" requirement. That means
>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
>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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