Hello everyone,
I have a antenna setup question as I am new to satellite operations so please bear with me...
I have a 2meter beam and a 70cm beam from my former adventures into VHF weak signal operations and was wondering about using them for satellite work.
Was thinking that since I don't have a az/el rotator yet, if I set them up on a single cross-boom with the TV rotator I have now, angle them with the elements at 45 degree angles and the booms angled 30 to 40 degrees front end up I might be able to get some decent ability into the FM satellites (AO51, SO50, AO27, ISS).
I already have the good coax for them (LMR-400) and a duplexor for my FT-857D. Was going to try to install the antennas on top of my storage building with a height of approx. 16 feet. That's the highest structure I can get onto that belongs to me.
Any alternate ideas or advice is always welcome as I said before this is all new to me.
Jacob Tennant - K8JWT Morgantown,WV FM09ap
About 15 degrees elevation is usually considered optimum.
On 12-Mar-10 01:32, Jacob Tennant wrote: and the booms angled 30 to 40 degrees
front end up
out here in 6 land I keep my 5 el on 2 mtr and 11 elements on 70cm (both horizontal) at 30 degs above my HF beam and miss very little on FM or SSB birds
N6RSX
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org]On Behalf Of Nigel Gunn G8IFF/W8IFF Sent: Thursday, March 11, 2010 6:26 PM To: k8jwt@comcast.net Cc: Amsat BB Subject: [amsat-bb] Re: Antenna setup
About 15 degrees elevation is usually considered optimum.
On 12-Mar-10 01:32, Jacob Tennant wrote: and the booms angled 30 to 40 degrees
front end up
About 15 degrees elevation is usually considered optimum.
...and the booms angled 30 to 40 degrees... up
Yes, NEVER higher than 15 degrees. You don't need the gain much above the horizon where the satellite is up to 10 dB CLOSER. You DO need the gain on the horizon where the satellite is 10 dB further away. See the plot on www.aprs.org/rotator1.html Pay particular attention to the scale drawing of a LEO orbit to the ground station.
Tracking a LEO satellite is like sitting 100 yards from an infinitely long east-west railroad track and using your beam to communicate with a train.
1) You point your antenna almost due west (-15 degrees or so) so that the infinite distance is still in the main beam PLUS all the track almost up to where you are. Then the approaching train is ALWAYS in your main beam until it is 100 yards away (where it is now 45 degrees from your location). But then it is so strong, you can hear it on a wet noodle.
2) For those three seconds as it goes by, it is not in your main beam, but it is so strong who cares.
3) Swing the beam now due east (minus about 15 degres) and again, for the entire rest of the pass, the train is in your main beam.
If you put your beam in either case 30 or 40 degrees away from the track, you would miss the MAJORITY of the time the train is traveling, because the MAJORITY of the time, it is far far away and not in your main beam.
We must dispell any literature that even hints that an angle above 15 degrees is good for LEO satellites (of course there are always exceptions)... For example, you live in a HOLE! Then it makes no sense to set your antenna at 15 degrees if that is still pinting into surrounding dirt. Common sense then applies.
Bob, WB4APR
Yes, NEVER higher than 15 degrees. You don't need the gain much above the horizon where the satellite is up to 10 dB CLOSER.
Bob,
Looks like you Navy guys have been using this technique since the early 1960's. Check out the photo "Radio Control Hut & Team Overseas" on http://www.globalsecurity.org/space/systems/grab.htm
-Joe KM1P
Hi Jacob,
My satelite antenna is 4 elements on 2 meters and 8 elements on 430 with a pre-amp mounted on the UHF boom. The UHF antenna is used for receive only. Take a look at it on QRZ.com under my call sign.
WA7HQD Lee Ernstrom Syracuse, Utah DN31xb
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Jacob Tennant Sent: Thursday, March 11, 2010 6:32 PM To: Amsat BB Subject: [amsat-bb] Antenna setup
Hello everyone,
I have a antenna setup question as I am new to satellite operations so please bear with me...
I have a 2meter beam and a 70cm beam from my former adventures into VHF weak signal operations and was wondering about using them for satellite work.
Was thinking that since I don't have a az/el rotator yet, if I set them up on a single cross-boom with the TV rotator I have now, angle them with the elements at 45 degree angles and the booms angled 30 to 40 degrees front end up I might be able to get some decent ability into the FM satellites (AO51, SO50, AO27, ISS).
I already have the good coax for them (LMR-400) and a duplexor for my FT-857D. Was going to try to install the antennas on top of my storage building with a height of approx. 16 feet. That's the highest structure I can get onto that belongs to me.
Any alternate ideas or advice is always welcome as I said before this is all new to me.
Jacob Tennant - K8JWT Morgantown,WV FM09ap
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participants (6)
-
D. Craig Fox -
Jacob Tennant -
Joe Fitzgerald -
Lee Ernstrom -
Nigel Gunn G8IFF/W8IFF -
Robert Bruninga