I have been using a 2.4 ghz Vagi antenna for my Mode S antenna the past few days. I am seeing quite a bit of signal droppout as AO-51 does a little rotating. With a circular polarized antenna do any better ? I have found a source for a 2.4ghz 10 db RHCP antenna and thought about trying that. I know I cant get it before AO-51 goes back to V/U mode but thought I could try that next time. The antenna I found has about a 50 degree pattern so I should get decent coverage since I have it pointed at a fixed elevation because I dont have an az/el rotor.
Ron KA4KYI
At 05:26 AM 5/10/2008, Ronald Nutter wrote:
I have been using a 2.4 ghz Vagi antenna for my Mode S antenna the past few days. I am seeing quite a bit of signal droppout as AO-51 does a little rotating. With a circular polarized antenna do any better ? I have found a source for a 2.4ghz 10 db RHCP antenna and thought about trying that. I know I cant get it before AO-51 goes back to V/U mode but thought I could try that next time. The antenna I found has about a 50 degree pattern so I should get decent coverage since I have it pointed at a fixed elevation because I dont have an az/el rotor.
Ron KA4KYI
Ron,
From what I have read on what others are using for 2.4 GHz (mode-S) on AO-51 (or other Leo sats) a 10-dB circular pol. antenna should work fine. As far as using it without elevation control I cannot tell you how that will work. Ten dB may be a bit too narrow for best operation at all elevations. But the gain would be good to have for the period of time the satellite is within your beam. I believe Bob Bruninga has found that a fixed elevation of 20-degrees makes a good solution when not moving elevation.
If the antenna is accessible you can experiment on what angle works best by trying it at several angles.
I plan to build my self a simple corner reflector fed with a dipole which should result in about 10-dB gain. I also have an 85cm dish with helix feed that was used for AO-40. I have two 2.4 -GHz LNA's and two Drake converters (123-MHz; 435-MHz output) so that any combination will be possible when all is re-installed. I have full az-el tracking.
***************************************************** 73, Ed - KL7UW BP40iq, 6m - 3cm 144-EME: FT-847, mgf-1801, 4x-xp20, 185w http://www.kl7uw.com AK VHF-Up Group NA Rep. for DUBUS: dubususa@hotmail.com *****************************************************
What got me thinking about the circular polarized type of antenna is to minimize the signal dropouts from the satellite as it spins. My other thought was to put a second antenna up, orient it horizontally and put a remote antenna switch in place so that I can flip between vertical and horizontal. Is my idea sound or am I barking up the wrong tree ?
Ron KA4KYI
Edward Cole wrote:
At 05:26 AM 5/10/2008, Ronald Nutter wrote:
I have been using a 2.4 ghz Vagi antenna for my Mode S antenna the past few days. I am seeing quite a bit of signal droppout as AO-51 does a little rotating. With a circular polarized antenna do any better ? I have found a source for a 2.4ghz 10 db RHCP antenna and thought about trying that. I know I cant get it before AO-51 goes back to V/U mode but thought I could try that next time. The antenna I found has about a 50 degree pattern so I should get decent coverage since I have it pointed at a fixed elevation because I dont have an az/el rotor.
Ron KA4KYI
Ron,
From what I have read on what others are using for 2.4 GHz (mode-S) on AO-51 (or other Leo sats) a 10-dB circular pol. antenna should work fine. As far as using it without elevation control I cannot tell you how that will work. Ten dB may be a bit too narrow for best operation at all elevations. But the gain would be good to have for the period of time the satellite is within your beam. I believe Bob Bruninga has found that a fixed elevation of 20-degrees makes a good solution when not moving elevation.
If the antenna is accessible you can experiment on what angle works best by trying it at several angles.
I plan to build my self a simple corner reflector fed with a dipole which should result in about 10-dB gain. I also have an 85cm dish with helix feed that was used for AO-40. I have two 2.4 -GHz LNA's and two Drake converters (123-MHz; 435-MHz output) so that any combination will be possible when all is re-installed. I have full az-el tracking.
73, Ed - KL7UW BP40iq, 6m - 3cm 144-EME: FT-847, mgf-1801, 4x-xp20, 185w http://www.kl7uw.com AK VHF-Up Group NA Rep. for DUBUS: dubususa@hotmail.com
Ron, AO-51 is linear polarized. A cicrular polarized antenna of either rotation will minimize fading from Spacecraft rotation. With a linear to circular you lose 3 dB of gain and you have no cancelation for ground and building reflections that can be more severe than Spacecraft rotation depending on terrain. Art, KC6UQH
----- Original Message ----- From: "Ronald Nutter" rnutter@networkref.com To: "Edward Cole" kl7uw@acsalaska.net Cc: amsat-bb@AMSAT.Org Sent: Saturday, May 10, 2008 2:43 PM Subject: [amsat-bb] Re: Mode S Antenna question
What got me thinking about the circular polarized type of antenna is to minimize the signal dropouts from the satellite as it spins. My other thought was to put a second antenna up, orient it horizontally and put a remote antenna switch in place so that I can flip between vertical and horizontal. Is my idea sound or am I barking up the wrong tree ?
Ron KA4KYI
participants (3)
-
Edward Cole -
kc6uqh -
Ronald Nutter