satellite average elevation & new birds
I'm kind of looking for an update from Bob, but can't find his email right now...
But the question is, in view of what appears to be some renewed interest in working the new cube sats, et al, is asking Bob to comment on his earlier thoughts on using antennae at fixed elevations. For me, I'm using my Elk on a Rat Shack rotor at a fixed el per Bob's recommendations. (I'm still struggling with PCSAT32...!!!%^&*!!) but, this antenna set up is very cost effective and seems to perform pretty well.
For example, Joel Black has asked for some advice in an earlier posting. My concern is that new operators or those returning run out and spend a bunch of $$$ on a new setup. No one knows how long the current crop will last or if a new crop is in the future, so probably some caution on the Visa is warranted.
Just asking (and especially Bob)
73, Ted K7TRK
-----Original Message----- From: amsat-bb-bounces@AMSAT.Org [mailto:amsat-bb-bounces@AMSAT.Org] On Behalf Of Bob Bruninga Sent: Tuesday, April 12, 2011 8:23 AM To: amsat-bb@AMSAT.Org Subject: [amsat-bb] Re: satellite average elevation
we used a horizontally polarized yagi fixed at 30 degrees above the horizon. That worked very well..
Thanks for the confirmation. Yes, elevation rotation is simply not needed at all for LEO spacecraft and modest beams. A mild, fixed tilt modest beam is just perfect.
But, the "30 degree" angle myth is very pervasive throughout amsat, whereas, the optimum angle is more like 15 degrees.
A 30 degree up-tilt gives up too much gain (-3 dB!) on the horizon where signals are weakest and where satellites spend most of their time, and puts the gain in an area of the sky where the satellite is already 6 dB stronger and is rarely there (giving you max beam gain where you need it least).
If you look at the sketches on the web page, the optimum angle is more like 15 degrees up-tilt. It preserves max gain on the horizon within 1 dB (where it is needed most) and focuses the breadth of its gain on the area of the sky where the satellites spend something like 95% of their time. For the missing 5%, the satellite is right on top of you and almost 10 dB stronger without any beam at all. Oh, and the 15 degree up-tilt beam is also perfect for Terrestrial operations as well.
See the sketch on: http://aprs.org/rotator1.html
In some future life, if we ever get back to HEO's and huge OSCAR arrays, then elevation rotors have a place. These high-gain beams have such narrow gain patterns, that higher precision tracking is a must. (Though it is complete overkill for LEO's).
Using these OVERKILL arrays for LEO's adds significant complexity to LEO operation requiring higher precision tracking, elevation rotors, better timing, fresher element sets and automated operation.
Using a TV rotator and 15 degree fixed tilt beam is much more forgiving...
Bob, Wb4APR
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Just a short time ago after I moved into a new shack, I operated for a month with an Elk at 15 degrees on a tripod. Armstrong rotor. I worked all the current satellites right up through the first week we had AO-73's transponder available.
Pay close attention to comments WB4APR has made about setting the fixed elevation based on the lowest horizon you can work. For example, if it takes ten degrees for you to clear a mountain, twenty five degrees is probably okay. If you have a clear horizon view, fifteen is probably okay. The goal is to have as much gain available at your lowest elevation to increase your available range. YMMV
PS A preamp goes a long way in a fixed elevation setup.
73 Clayton W5PFG On Dec 17, 2013 7:24 PM, "Ted" k7trkradio@charter.net wrote:
I'm kind of looking for an update from Bob, but can't find his email right now...
But the question is, in view of what appears to be some renewed interest in working the new cube sats, et al, is asking Bob to comment on his earlier thoughts on using antennae at fixed elevations. For me, I'm using my Elk on a Rat Shack rotor at a fixed el per Bob's recommendations. (I'm still struggling with PCSAT32...!!!%^&*!!) but, this antenna set up is very cost effective and seems to perform pretty well.
For example, Joel Black has asked for some advice in an earlier posting. My concern is that new operators or those returning run out and spend a bunch of $$$ on a new setup. No one knows how long the current crop will last or if a new crop is in the future, so probably some caution on the Visa is warranted.
Just asking (and especially Bob)
73, Ted K7TRK
-----Original Message----- From: amsat-bb-bounces@AMSAT.Org [mailto:amsat-bb-bounces@AMSAT.Org] On Behalf Of Bob Bruninga Sent: Tuesday, April 12, 2011 8:23 AM To: amsat-bb@AMSAT.Org Subject: [amsat-bb] Re: satellite average elevation
we used a horizontally polarized yagi fixed at 30 degrees above the horizon. That worked very well..
Thanks for the confirmation. Yes, elevation rotation is simply not needed at all for LEO spacecraft and modest beams. A mild, fixed tilt modest beam is just perfect.
But, the "30 degree" angle myth is very pervasive throughout amsat, whereas, the optimum angle is more like 15 degrees.
A 30 degree up-tilt gives up too much gain (-3 dB!) on the horizon where signals are weakest and where satellites spend most of their time, and puts the gain in an area of the sky where the satellite is already 6 dB stronger and is rarely there (giving you max beam gain where you need it least).
If you look at the sketches on the web page, the optimum angle is more like 15 degrees up-tilt. It preserves max gain on the horizon within 1 dB (where it is needed most) and focuses the breadth of its gain on the area of the sky where the satellites spend something like 95% of their time. For the missing 5%, the satellite is right on top of you and almost 10 dB stronger without any beam at all. Oh, and the 15 degree up-tilt beam is also perfect for Terrestrial operations as well.
See the sketch on: http://aprs.org/rotator1.html
In some future life, if we ever get back to HEO's and huge OSCAR arrays, then elevation rotors have a place. These high-gain beams have such narrow gain patterns, that higher precision tracking is a must. (Though it is complete overkill for LEO's).
Using these OVERKILL arrays for LEO's adds significant complexity to LEO operation requiring higher precision tracking, elevation rotors, better timing, fresher element sets and automated operation.
Using a TV rotator and 15 degree fixed tilt beam is much more forgiving...
Bob, Wb4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
... asking Bob to comment on his earlier thoughts on using antennae at
fixed elevations?
The geometry of LEO satellites has not changed. The optimum angle for a fixed tilt modest gain YAGI is about 15 degrees (assuming you have a decent horizon). See: http://aprs.org/LEO-tracking.html
That said, if your antenna is seriously blocked from all directions below say 10 degrees, then you are not going to hear anything down there anyway. So bump it up to say 20 or 25. But 70% of all LEO passes are below 22 degrees so just recognize that you are giving up most of your operations.
Bob, Wb4aPR
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Clayton Coleman Sent: Tuesday, December 17, 2013 8:35 PM To: Ted Cc: AMSAT-BB Subject: [amsat-bb] Re: satellite average elevation & new birds
Just a short time ago after I moved into a new shack, I operated for a month with an Elk at 15 degrees on a tripod. Armstrong rotor. I worked all the current satellites right up through the first week we had AO-73's transponder available.
Pay close attention to comments WB4APR has made about setting the fixed elevation based on the lowest horizon you can work. For example, if it takes ten degrees for you to clear a mountain, twenty five degrees is probably okay. If you have a clear horizon view, fifteen is probably okay. The goal is to have as much gain available at your lowest elevation to increase your available range. YMMV
PS A preamp goes a long way in a fixed elevation setup.
73 Clayton W5PFG On Dec 17, 2013 7:24 PM, "Ted" k7trkradio@charter.net wrote:
I'm kind of looking for an update from Bob, but can't find his email right now...
But the question is, in view of what appears to be some renewed interest in working the new cube sats, et al, is asking Bob to comment on his earlier thoughts on using antennae at fixed elevations. For me, I'm using my Elk on a Rat Shack rotor at a fixed el per Bob's recommendations. (I'm still struggling with PCSAT32...!!!%^&*!!) but, this antenna set up is very cost effective and seems to perform pretty
well.
For example, Joel Black has asked for some advice in an earlier posting. My concern is that new operators or those returning run out and spend a bunch of $$$ on a new setup. No one knows how long the current crop will last or if a new crop is in the future, so probably some caution on the Visa is warranted.
Just asking (and especially Bob)
73, Ted K7TRK
-----Original Message----- From: amsat-bb-bounces@AMSAT.Org [mailto:amsat-bb-bounces@AMSAT.Org] On Behalf Of Bob Bruninga Sent: Tuesday, April 12, 2011 8:23 AM To: amsat-bb@AMSAT.Org Subject: [amsat-bb] Re: satellite average elevation
we used a horizontally polarized yagi fixed at 30 degrees above the horizon. That worked very well..
Thanks for the confirmation. Yes, elevation rotation is simply not needed at all for LEO spacecraft and modest beams. A mild, fixed tilt modest beam is just perfect.
But, the "30 degree" angle myth is very pervasive throughout amsat, whereas, the optimum angle is more like 15 degrees.
A 30 degree up-tilt gives up too much gain (-3 dB!) on the horizon where signals are weakest and where satellites spend most of their time, and puts the gain in an area of the sky where the satellite is already 6 dB stronger and is rarely there (giving you max beam gain
where you need it least).
If you look at the sketches on the web page, the optimum angle is more like 15 degrees up-tilt. It preserves max gain on the horizon within 1 dB (where it is needed most) and focuses the breadth of its gain on the area of the sky where the satellites spend something like 95% of their time. For the missing 5%, the satellite is right on top of you and almost 10 dB stronger without any beam at all. Oh, and the 15 degree up-tilt beam is also perfect for Terrestrial operations as well.
See the sketch on: http://aprs.org/rotator1.html
In some future life, if we ever get back to HEO's and huge OSCAR arrays, then elevation rotors have a place. These high-gain beams have such narrow gain patterns, that higher precision tracking is a must. (Though it is complete overkill for LEO's).
Using these OVERKILL arrays for LEO's adds significant complexity to LEO operation requiring higher precision tracking, elevation rotors, better timing, fresher element sets and automated operation.
Using a TV rotator and 15 degree fixed tilt beam is much more
forgiving...
Bob, Wb4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (3)
-
Clayton Coleman -
Robert Bruninga -
Ted