Steve,
I have both a commercial and a homebrew Eggbeater and am disappointed with both, especially in light of its rather high price. Connected to my IC-7000 via an ARR mast-mounted preamp, performance is far less than with an HT and an Arrow. Guess an omni can't cut it, at least not from my QTH.
Maybe if I could get it up higher, clear of all roofs, it would do better. I can make contacts at relatively high sat elevations, but can do just as well with a $10 dual band ground plane. My friend has an Eggbeater and the same preamp at a clearer QTH, and he hears substantially better, down to 10 degrees elevation in some directions.
Good luck and 73, Bill NZ5N
Hi Steve,
It is surprising to read that you are not hearing
anything. I have
repeatedly used a 2m and 70cm Eggbeater for the sats
and have had no
problem hearing things. No pre-amp.
I was using a short cable (e.g. less than 10 meters).
The rigs I
used were a FT-736r (deaf) and a FT-847 (so-so).
73,
Dave
Consider trying AA2TX's excellent parasitic lindenblad design. Unlike the overpriced eggbeater, it puts the gain on the horizon where it is needed, and is circular across the pattern. The parts mostly are from your local hardware store, and in Tony's typical fashion, it is simple to assemble and works well.
73, Drew KO4MA
----- Original Message ----- From: "Bill Dzurilla" billdz.geo@yahoo.com To: amsat-bb@amsat.org Sent: Thursday, April 16, 2009 11:56 AM Subject: [amsat-bb] Re: EggBeater
Steve,
I have both a commercial and a homebrew Eggbeater and am disappointed with both, especially in light of its rather high price. Connected to my IC-7000 via an ARR mast-mounted preamp, performance is far less than with an HT and an Arrow. Guess an omni can't cut it, at least not from my QTH.
Maybe if I could get it up higher, clear of all roofs, it would do better. I can make contacts at relatively high sat elevations, but can do just as well with a $10 dual band ground plane. My friend has an Eggbeater and the same preamp at a clearer QTH, and he hears substantially better, down to 10 degrees elevation in some directions.
Good luck and 73, Bill NZ5N
Hi Steve,
It is surprising to read that you are not hearing
anything. I have
repeatedly used a 2m and 70cm Eggbeater for the sats
and have had no
problem hearing things. No pre-amp.
I was using a short cable (e.g. less than 10 meters).
The rigs I
used were a FT-736r (deaf) and a FT-847 (so-so).
73,
Dave
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
Drew,
Thanks for the document on this antenna. I was going to try resizing the 2m Lindenblad design of Tony's but this will be a snap for me. I have 1/8-inch rod elements from an old Cushcraft yagi that disintegrated long ago and have some 1/2-inch sched-40 aluminum pipe (7/8 inch OD) that will work fine for the vertical. I can get the PVC from my local building supply. Only need to order ferrites from Mouser. Since I will place a 432 preamp at the antenna a short run of RG-58 or mini-8 will suffice. I probably will make some variation in the materials used. I did that on the 2m Lindenblad (not assembled, yet).
73, Ed - KL7UW
At 08:02 AM 4/16/2009, Andrew Glasbrenner wrote:
Consider trying AA2TX's excellent parasitic lindenblad design. Unlike the overpriced eggbeater, it puts the gain on the horizon where it is needed, and is circular across the pattern. The parts mostly are from your local hardware store, and in Tony's typical fashion, it is simple to assemble and works well.
73, Drew KO4MA
----- Original Message ----- From: "Bill Dzurilla" billdz.geo@yahoo.com To: amsat-bb@amsat.org Sent: Thursday, April 16, 2009 11:56 AM Subject: [amsat-bb] Re: EggBeater
Steve,
I have both a commercial and a homebrew Eggbeater and am disappointed with both, especially in light of its rather high price. Connected to my IC-7000 via an ARR mast-mounted preamp, performance is far less than with an HT and an Arrow. Guess an omni can't cut it, at least not from my QTH.
Maybe if I could get it up higher, clear of all roofs, it would do better. I can make contacts at relatively high sat elevations, but can do just as well with a $10 dual band ground plane. My friend has an Eggbeater and the same preamp at a clearer QTH, and he hears substantially better, down to 10 degrees elevation in some directions.
Good luck and 73, Bill NZ5N
Hi Steve,
It is surprising to read that you are not hearing
anything. I have
repeatedly used a 2m and 70cm Eggbeater for the sats
and have had no
problem hearing things. No pre-amp.
I was using a short cable (e.g. less than 10 meters).
The rigs I
used were a FT-736r (deaf) and a FT-847 (so-so).
73,
Dave
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
Hello, can I ask a question related to this several-years old thread? At George Washington University, this fall we will be on the air and are buliding up an amateur radio club ground station from scratch. Currently we are collecting equipment, cables, etc., while we wait for the construction to begin on a new door in the interior of a third floor class room space to let us use that area as a "radio room" or something like that. At my home QTH, I'm testing out the radios we can use, and would like to both receive and transmit - with omni antennas (e.g., eggbeaters, QHA ) and later AZ-El yagis.
Assuming an LNA is used at the antenna for the RX path, would it be practical to use that same omni for uplink? What are the recommended power settings for such an uplink for any of the recent amsats?
If there was a constraint (for the summer into fall) of operating in a limited visibility area, and approximately 50 sq. ft of open access (i.e., 21 ft monopole mast with open free area about 4 ft dia.) would that be adequate for any sort of uplink antenna? The good thing is that the ultimate location of the club station antenna farm is huge, but for now this is what we have. I'm open to AZ-El positioners but the mast loading limit is pretty small for now.
Any suggestion welcome.
Regards,
Samudra N3RDX
On Thu, Apr 16, 2009 at 9:50 PM, Edward Cole kl7uw@acsalaska.net wrote:
Drew,
Thanks for the document on this antenna. I was going to try resizing the 2m Lindenblad design of Tony's but this will be a snap for me. I have 1/8-inch rod elements from an old Cushcraft yagi that disintegrated long ago and have some 1/2-inch sched-40 aluminum pipe (7/8 inch OD) that will work fine for the vertical. I can get the PVC from my local building supply. Only need to order ferrites from Mouser. Since I will place a 432 preamp at the antenna a short run of RG-58 or mini-8 will suffice. I probably will make some variation in the materials used. I did that on the 2m Lindenblad (not assembled, yet).
73, Ed - KL7UW
At 08:02 AM 4/16/2009, Andrew Glasbrenner wrote:
Consider trying AA2TX's excellent parasitic lindenblad design. Unlike the overpriced eggbeater, it puts the gain on the horizon where it is needed, and is circular across the pattern. The parts mostly are from your local hardware store, and in Tony's typical fashion, it is simple to assemble
and
works well.
73, Drew KO4MA
----- Original Message ----- From: "Bill Dzurilla" billdz.geo@yahoo.com To: amsat-bb@amsat.org Sent: Thursday, April 16, 2009 11:56 AM Subject: [amsat-bb] Re: EggBeater
Steve,
I have both a commercial and a homebrew Eggbeater and am disappointed
with
both, especially in light of its rather high price. Connected to my IC-7000 via an ARR mast-mounted preamp, performance is far less than
with
an HT and an Arrow. Guess an omni can't cut it, at least not from my
QTH.
Maybe if I could get it up higher, clear of all roofs, it would do
better.
I can make contacts at relatively high sat elevations, but can do just
as
well with a $10 dual band ground plane. My friend has an Eggbeater and the same preamp at a clearer QTH, and he hears substantially better,
down
to 10 degrees elevation in some directions.
Good luck and 73, Bill NZ5N
Hi Steve,
It is surprising to read that you are not hearing
anything. I have
repeatedly used a 2m and 70cm Eggbeater for the sats
and have had no
problem hearing things. No pre-amp.
I was using a short cable (e.g. less than 10 meters).
The rigs I
used were a FT-736r (deaf) and a FT-847 (so-so).
73,
Dave
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
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Hi Samudra, consider a better alternative to the 'egg beater': Moxon turnstile....much better performance. I will e-mail the article from qst. Also, consider an Elk 2m/440 yagi at a fixed elevation and on a Radio Shack rotor.
GL, Ted, K7TRK
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Samudra Haque Sent: Tuesday, May 29, 2012 1:18 PM To: Edward Cole Cc: amsat-bb@amsat.org Subject: [amsat-bb] Re: EggBeater
Hello, can I ask a question related to this several-years old thread? At George Washington University, this fall we will be on the air and are buliding up an amateur radio club ground station from scratch. Currently we are collecting equipment, cables, etc., while we wait for the construction to begin on a new door in the interior of a third floor class room space to let us use that area as a "radio room" or something like that. At my home QTH, I'm testing out the radios we can use, and would like to both receive and transmit - with omni antennas (e.g., eggbeaters, QHA ) and later AZ-El yagis.
Assuming an LNA is used at the antenna for the RX path, would it be practical to use that same omni for uplink? What are the recommended power settings for such an uplink for any of the recent amsats?
If there was a constraint (for the summer into fall) of operating in a limited visibility area, and approximately 50 sq. ft of open access (i.e., 21 ft monopole mast with open free area about 4 ft dia.) would that be adequate for any sort of uplink antenna? The good thing is that the ultimate location of the club station antenna farm is huge, but for now this is what we have. I'm open to AZ-El positioners but the mast loading limit is pretty small for now.
Any suggestion welcome.
Regards,
Samudra N3RDX
On Thu, Apr 16, 2009 at 9:50 PM, Edward Cole kl7uw@acsalaska.net wrote:
Drew,
Thanks for the document on this antenna. I was going to try resizing the 2m Lindenblad design of Tony's but this will be a snap for me. I have 1/8-inch rod elements from an old Cushcraft yagi that disintegrated long ago and have some 1/2-inch sched-40 aluminum pipe (7/8 inch OD) that will work fine for the vertical. I can get the PVC from my local building supply. Only need to order ferrites from Mouser. Since I will place a 432 preamp at the antenna a short run of RG-58 or mini-8 will suffice. I probably will make some variation in the materials used. I did that on the 2m Lindenblad (not assembled, yet).
73, Ed - KL7UW
At 08:02 AM 4/16/2009, Andrew Glasbrenner wrote:
Consider trying AA2TX's excellent parasitic lindenblad design. Unlike the overpriced eggbeater, it puts the gain on the horizon where it is needed, and is circular across the pattern. The parts mostly are from your local hardware store, and in Tony's typical fashion, it is simple to assemble
and
works well.
73, Drew KO4MA
----- Original Message ----- From: "Bill Dzurilla" billdz.geo@yahoo.com To: amsat-bb@amsat.org Sent: Thursday, April 16, 2009 11:56 AM Subject: [amsat-bb] Re: EggBeater
Steve,
I have both a commercial and a homebrew Eggbeater and am disappointed
with
both, especially in light of its rather high price. Connected to my IC-7000 via an ARR mast-mounted preamp, performance is far less than
with
an HT and an Arrow. Guess an omni can't cut it, at least not from my
QTH.
Maybe if I could get it up higher, clear of all roofs, it would do
better.
I can make contacts at relatively high sat elevations, but can do just
as
well with a $10 dual band ground plane. My friend has an Eggbeater
and
the same preamp at a clearer QTH, and he hears substantially better,
down
to 10 degrees elevation in some directions.
Good luck and 73, Bill NZ5N
Hi Steve,
It is surprising to read that you are not hearing
anything. I have
repeatedly used a 2m and 70cm Eggbeater for the sats
and have had no
problem hearing things. No pre-amp.
I was using a short cable (e.g. less than 10 meters).
The rigs I
used were a FT-736r (deaf) and a FT-847 (so-so).
73,
Dave
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
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Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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I was actually reading up on Bob Bruninga's analysis (earlier in this thread) of why a fixed elevation yagi would have more than adequate performance for majority of the LEO passes, when you sent me the info below. Thank you!
Comment: based upon what you sent in a separate message, the picture of a "mean" looking in-service 5-element model, if the antenna is that small of a mass, a second revolute joint for Elevation control with positioner could be practical - if some parts from hobby robotics / class room robotics projects were able to be used. Of course it would increase the cost somewhat and complicate wiring - but would result in true elevation over azimuth control.
73 de N3RDX
On Tue, May 29, 2012 at 4:49 PM, Ted k7trkradio@charter.net wrote:
Hi Samudra, consider a better alternative to the 'egg beater': Moxon turnstile....much better performance. I will e-mail the article from qst. Also, consider an Elk 2m/440 yagi at a fixed elevation and on a Radio Shack rotor.
GL, Ted, K7TRK
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Samudra Haque Sent: Tuesday, May 29, 2012 1:18 PM To: Edward Cole Cc: amsat-bb@amsat.org Subject: [amsat-bb] Re: EggBeater
Hello, can I ask a question related to this several-years old thread? At George Washington University, this fall we will be on the air and are buliding up an amateur radio club ground station from scratch. Currently we are collecting equipment, cables, etc., while we wait for the construction to begin on a new door in the interior of a third floor class room space to let us use that area as a "radio room" or something like that. At my home QTH, I'm testing out the radios we can use, and would like to both receive and transmit - with omni antennas (e.g., eggbeaters, QHA ) and later AZ-El yagis.
Assuming an LNA is used at the antenna for the RX path, would it be practical to use that same omni for uplink? What are the recommended power settings for such an uplink for any of the recent amsats?
If there was a constraint (for the summer into fall) of operating in a limited visibility area, and approximately 50 sq. ft of open access (i.e., 21 ft monopole mast with open free area about 4 ft dia.) would that be adequate for any sort of uplink antenna? The good thing is that the ultimate location of the club station antenna farm is huge, but for now this is what we have. I'm open to AZ-El positioners but the mast loading limit is pretty small for now.
Any suggestion welcome.
Regards,
Samudra N3RDX
On Thu, Apr 16, 2009 at 9:50 PM, Edward Cole kl7uw@acsalaska.net wrote:
Drew,
Thanks for the document on this antenna. I was going to try resizing the 2m Lindenblad design of Tony's but this will be a snap for me. I have 1/8-inch rod elements from an old Cushcraft yagi that disintegrated long ago and have some 1/2-inch sched-40 aluminum pipe (7/8 inch OD) that will work fine for the vertical. I can get the PVC from my local building supply. Only need to order ferrites from Mouser. Since I will place a 432 preamp at the antenna a short run of RG-58 or mini-8 will suffice. I probably will make some variation in the materials used. I did that on the 2m Lindenblad (not assembled, yet).
73, Ed - KL7UW
At 08:02 AM 4/16/2009, Andrew Glasbrenner wrote:
Consider trying AA2TX's excellent parasitic lindenblad design. Unlike
the
overpriced eggbeater, it puts the gain on the horizon where it is
needed,
and is circular across the pattern. The parts mostly are from your local hardware store, and in Tony's typical fashion, it is simple to assemble
and
works well.
73, Drew KO4MA
----- Original Message ----- From: "Bill Dzurilla" billdz.geo@yahoo.com To: amsat-bb@amsat.org Sent: Thursday, April 16, 2009 11:56 AM Subject: [amsat-bb] Re: EggBeater
Steve,
I have both a commercial and a homebrew Eggbeater and am disappointed
with
both, especially in light of its rather high price. Connected to my IC-7000 via an ARR mast-mounted preamp, performance is far less than
with
an HT and an Arrow. Guess an omni can't cut it, at least not from my
QTH.
Maybe if I could get it up higher, clear of all roofs, it would do
better.
I can make contacts at relatively high sat elevations, but can do
just
as
well with a $10 dual band ground plane. My friend has an Eggbeater
and
the same preamp at a clearer QTH, and he hears substantially better,
down
to 10 degrees elevation in some directions.
Good luck and 73, Bill NZ5N
Hi Steve,
It is surprising to read that you are not hearing
anything. I have
repeatedly used a 2m and 70cm Eggbeater for the sats
and have had no
problem hearing things. No pre-amp.
I was using a short cable (e.g. less than 10 meters).
The rigs I
used were a FT-736r (deaf) and a FT-847 (so-so).
73,
Dave
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
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Hello,
I tottaly agree with Ted, i have a single moxon (not turnstile) for VHF LEO satellite and works quite good. Also i have another, a moxon turnstile for 436 LEO satellites and it work relatively fine, but average gain is only good enough for SSB satellites. For FM reception a good LNA is mandatory. Right now i don't have any LNA neither for VHF or UHF (that's why I always work AO-27 with my arrow antenna). I can tell you that even a single moxon is almost enough, at least for VHF, for UHF the signal loss is greater so the incoming signal is not enough for FM, but i can at least hear and see on the FFT spectrum display any SSB or CW, they usually show up with at least10dB over the noise background.
The moxon are greats but a good LNA just after the antenna will be very helpfull. One more thing, for a smoth recieving pattern is better to put the antenna close to the roof, this avoid the nulls and fadings but compromise the reception at low elevation angles.
Well, that's all. Just my little experience with these great antennas. Good Luck all,
73!!!
Raydel, CM2ESP
----- Original Message ----- From: "Ted" k7trkradio@charter.net To: "'Samudra Haque'" samudra.haque@gmail.com; "'Edward Cole'" kl7uw@acsalaska.net Cc: amsat-bb@amsat.org Sent: Tuesday, May 29, 2012 4:49 PM Subject: [amsat-bb] Re: EggBeater
Hi Samudra, consider a better alternative to the 'egg beater': Moxon turnstile....much better performance. I will e-mail the article from qst. Also, consider an Elk 2m/440 yagi at a fixed elevation and on a Radio Shack rotor.
GL, Ted, K7TRK
Este mensaje ha sido enviado mediante el servicio de correo electronico que ofrece la Federacion de Radioaficionados de Cuba a sus miembros para respaldar el cumplimiento de los objetivos de la organizacion y su politica informativa. La persona que envia este correo asume el compromiso de usar el servicio a tales fines y cumplir con las regulaciones establecidas.
I have both a commercial and a homebrew Eggbeater and am disappointed with both,
Yes, because the best omni in the world is no better (generally) than a dipole made out of a piece of wire. By definition, these antennas are OMNI's so they can hear in all directions. This means they have zero gain. That is the basic law of physics.
... performance is far less than with an HT and an Arrow.
This is because the arrow is a "gain" antenna. Gain means that the structure sacrifices gain in all directions to concentrate it in only one direction. Which then you have to point. It is impossible to have both gain and omni at the same time.
But what about Gain Vertical OMNI antennas? Well, they have GAIN in all directions but only on the horizon. To get that gain on the horizon, they MUST sacrifice gain somewhere else. They sacrifice all gain that is UP. But that is where satellites are, so it makes little sense to try to use one of these, because you still wont hear any satelites, because the gain you get "on the horizon" (maybe 3 to 6 dB or so) is just barely enough, but then as the satellite gets higher, it gets into the null of the antenna.
Guess an omni can't cut it, at least not from my QTH.
Yes, by definition. An omni cannot hear most of the amateur satellites on the horizon, because there just isnt enough signal (except for ISS). You need some gain to hear them on the horizon. BUT when the satellite gets above 20 to 30 degrees, it can be TEN times stronger and then ANY omni antenna will work quite well (and you don't have to point it).
BUT... plot the amount of time a satellite is in view above 25 degrees and it is less than 1/4th of the time.
So there is no free lunch. Either put up an omni and only be able to hear the satellites for on the order of 25% or less of their available time in view (but have no moving parts). Or use a beam to get the gain on the horizon where you need it most, and plan on keeping it pointed at the satellite.
Maybe if I could get it up higher, clear of all roofs, it would do better.
Not really. Because getting "high" only gets you visiblity to the horizon where, by definition, you already do not have enough gain to hear any of the low powered satellites.
I can make contacts at relatively high sat elevations, but can do just as well with a $10 dual band ground plane.
Yes! That is exactly what we are talking about here. You cannot have both. If you want an omni, then a simple ground plane antenna made out of a few pieces of wire will do just about as good most of the time as the most expensive "omni"... Some will argue that you need circular polarization, to eliminate some fading, but again you can also say that many times the polarization is opposite and so even the right hand circular antnena hears fades too when the circularity gets reversed...
Go with a simple 1/4 wave ground plane antenna with a preamp, and hear well, less than 1/3rd of the time. Or us a beam...
My friend has an Eggbeater and the same preamp at a clearer QTH, and he hears substantially better, down to 10 degrees elevation in some directions.
Yes, some satellites are stronger than others. But most are not designed with the 10dB link margin they need to hit omni's horizon to horizon. Most cannot afford to waste that much power for the benefit of people with omni's.
Plenty of people corrrectly swear by their omni that it can hear very well. And tthis is true, but not at low elevations -and- with the low power satellites. So always make sure you are comparing apples and apples.
I was shocked during a class today when I went out to listen to VO-52 and the signals sounded like 20 over S9... But then 30 seconds later, they were down where I expected. Looking at the track, it was almost directly overhead (and 10 dB) stronger than when it is a few minutes later.
Good luck Bob, WB4APR
adding to what Bob said Somewhere I read where the percentages of where the satellites are in elevation. The majority of low elevation is fairly high. Whereas as a elevation of 70 plus degrees is quite low. Then a higher elevation is closer so the path loss is less. Almost everyone that I know who started out with a egg beater eventually gets a beam of some sort. So why not start there? A simple short beam aimed at about 30 degrees will cover a huge amount of sky 73 Bob W7LRD
----- Original Message -----
From: Robert Bruninga
To: billdz geo , amsat-bb@amsat.org
Sent: Thu, 16 Apr 2009 17:36:45 +0000 (UTC)
Subject: [amsat-bb] Re: EggBeater
I have both a commercial and a homebrew Eggbeater
and am disappointed with both,
Yes, because the best omni in the world is no better (generally)
than a dipole made out of a piece of wire. By definition, these
antennas are OMNI's so they can hear in all directions. This
means they have zero gain. That is the basic law of physics.
... performance is far less than with an HT and
an Arrow.
This is because the arrow is a "gain" antenna. Gain means that
the structure sacrifices gain in all directions to concentrate
it in only one direction. Which then you have to point. It is
impossible to have both gain and omni at the same time.
But what about Gain Vertical OMNI antennas? Well, they have
GAIN in all directions but only on the horizon. To get that
gain on the horizon, they MUST sacrifice gain somewhere else.
They sacrifice all gain that is UP. But that is where
satellites are, so it makes little sense to try to use one of
these, because you still wont hear any satelites, because the
gain you get "on the horizon" (maybe 3 to 6 dB or so) is just
barely enough, but then as the satellite gets higher, it gets
into the null of the antenna.
Guess an omni can't cut it, at least not from my QTH.
Yes, by definition. An omni cannot hear most of the amateur
satellites on the horizon, because there just isnt enough signal
(except for ISS). You need some gain to hear them on the
horizon. BUT when the satellite gets above 20 to 30 degrees, it
can be TEN times stronger and then ANY omni antenna will work
quite well (and you don't have to point it).
BUT... plot the amount of time a satellite is in view above 25
degrees and it is less than 1/4th of the time.
So there is no free lunch. Either put up an omni and only be
able to hear the satellites for on the order of 25% or less of
their available time in view (but have no moving parts). Or use
a beam to get the gain on the horizon where you need it most,
and plan on keeping it pointed at the satellite.
Maybe if I could get it up higher, clear of all
roofs, it would do better.
Not really. Because getting "high" only gets you visiblity to
the horizon where, by definition, you already do not have enough
gain to hear any of the low powered satellites.
I can make contacts at relatively high sat
elevations, but can do just as well with a
$10 dual band ground plane.
Yes! That is exactly what we are talking about here. You
cannot have both. If you want an omni, then a simple ground
plane antenna made out of a few pieces of wire will do just
about as good most of the time as the most expensive "omni"...
Some will argue that you need circular polarization, to
eliminate some fading, but again you can also say that many
times the polarization is opposite and so even the right hand
circular antnena hears fades too when the circularity gets
reversed...
Go with a simple 1/4 wave ground plane antenna with a preamp,
and hear well, less than 1/3rd of the time. Or us a beam...
My friend has an Eggbeater and the same preamp
at a clearer QTH, and he hears substantially better,
down to 10 degrees elevation in some directions.
Yes, some satellites are stronger than others. But most are not
designed with the 10dB link margin they need to hit omni's
horizon to horizon. Most cannot afford to waste that much power
for the benefit of people with omni's.
Plenty of people corrrectly swear by their omni that it can hear
very well. And tthis is true, but not at low elevations -and-
with the low power satellites. So always make sure you are
comparing apples and apples.
I was shocked during a class today when I went out to listen to
VO-52 and the signals sounded like 20 over S9... But then 30
seconds later, they were down where I expected. Looking at the
track, it was almost directly overhead (and 10 dB) stronger than
when it is a few minutes later.
Good luck
Bob, WB4APR
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Somewhere I read where the percentages of where the satellites are in elevation. The majority of low elevation is fairly high. Whereas as a elevation of 70 plus degrees is quite low.
I have a table on my web page: www.aprs.org/rotator1.html
And looking at the figure it is obvious what we are saying.
Also there is a plot of a modest 6 element beam tilted up at 15 degrees (NO MORE!) showing how it and a TV rotator are all you need to work all these LEO birds.
Bob, WB4APR
Then a higher elevation is closer so the path
loss is less. Almost everyone that I know who started out with a egg beater eventually gets a beam of some sort. So why not start there? A simple short beam aimed at about 30 degrees will cover a huge amount of sky 73 Bob W7LRD
----- Original Message -----
From: Robert Bruninga
To: billdz geo , amsat-bb@amsat.org
Sent: Thu, 16 Apr 2009 17:36:45 +0000 (UTC)
Subject: [amsat-bb] Re: EggBeater
I have both a commercial and a homebrew Eggbeater
and am disappointed with both,
Yes, because the best omni in the world is no better
(generally)
than a dipole made out of a piece of wire. By definition,
these
antennas are OMNI's so they can hear in all directions. This
means they have zero gain. That is the basic law of physics.
... performance is far less than with an HT and
an Arrow.
This is because the arrow is a "gain" antenna. Gain means
that
the structure sacrifices gain in all directions to concentrate
it in only one direction. Which then you have to point. It
is
impossible to have both gain and omni at the same time.
But what about Gain Vertical OMNI antennas? Well, they have
GAIN in all directions but only on the horizon. To get that
gain on the horizon, they MUST sacrifice gain somewhere else.
They sacrifice all gain that is UP. But that is where
satellites are, so it makes little sense to try to use one of
these, because you still wont hear any satelites, because the
gain you get "on the horizon" (maybe 3 to 6 dB or so) is just
barely enough, but then as the satellite gets higher, it gets
into the null of the antenna.
Guess an omni can't cut it, at least not from my QTH.
Yes, by definition. An omni cannot hear most of the amateur
satellites on the horizon, because there just isnt enough
signal
(except for ISS). You need some gain to hear them on the
horizon. BUT when the satellite gets above 20 to 30 degrees,
it
can be TEN times stronger and then ANY omni antenna will work
quite well (and you don't have to point it).
BUT... plot the amount of time a satellite is in view above 25
degrees and it is less than 1/4th of the time.
So there is no free lunch. Either put up an omni and only be
able to hear the satellites for on the order of 25% or less of
their available time in view (but have no moving parts). Or
use
a beam to get the gain on the horizon where you need it most,
and plan on keeping it pointed at the satellite.
Maybe if I could get it up higher, clear of all
roofs, it would do better.
Not really. Because getting "high" only gets you visiblity to
the horizon where, by definition, you already do not have
enough
gain to hear any of the low powered satellites.
I can make contacts at relatively high sat
elevations, but can do just as well with a
$10 dual band ground plane.
Yes! That is exactly what we are talking about here. You
cannot have both. If you want an omni, then a simple ground
plane antenna made out of a few pieces of wire will do just
about as good most of the time as the most expensive "omni"...
Some will argue that you need circular polarization, to
eliminate some fading, but again you can also say that many
times the polarization is opposite and so even the right hand
circular antnena hears fades too when the circularity gets
reversed...
Go with a simple 1/4 wave ground plane antenna with a preamp,
and hear well, less than 1/3rd of the time. Or us a beam...
My friend has an Eggbeater and the same preamp
at a clearer QTH, and he hears substantially better,
down to 10 degrees elevation in some directions.
Yes, some satellites are stronger than others. But most are
not
designed with the 10dB link margin they need to hit omni's
horizon to horizon. Most cannot afford to waste that much
power
for the benefit of people with omni's.
Plenty of people corrrectly swear by their omni that it can
hear
very well. And tthis is true, but not at low elevations -and-
with the low power satellites. So always make sure you are
comparing apples and apples.
I was shocked during a class today when I went out to listen
to
VO-52 and the signals sounded like 20 over S9... But then 30
seconds later, they were down where I expected. Looking at
the
track, it was almost directly overhead (and 10 dB) stronger
than
when it is a few minutes later.
Good luck
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:
Yes, by definition. An omni cannot hear most of the amateur satellites on the horizon, because there just isnt enough signal (except for ISS). You need some gain to hear them on the horizon. BUT when the satellite gets above 20 to 30 degrees, it can be TEN times stronger and then ANY omni antenna will work quite well (and you don't have to point it).
BUT... plot the amount of time a satellite is in view above 25 degrees and it is less than 1/4th of the time.
Good point.
One approach I have tried with VO52 is to use two receivers with different antennas for the down link. (ie, one antenna is a ground plane with a modest degree of gain at the horizion, the other is a horizontally polarized (with respect to the ground) dipole.) The results are signficantly better than a single omni antenna and one of the receivers is usually able to produce an acceptable signal. During high over head passes the nulls in the pattern of the ground plane are quite apparent, and the dipole works much better on the high passes, on low passes the gain of the ground plane is helpfull but the signals while readable often won't even move the S meter. A beam that can be pointed directly at the satellite is an even better solution and is likely more cost effective if you are buying all the gear from scratch and listening to signals that often don't move the S meter can be tiring after a while.
Still in my view if you can't have or don't want a beam and rotor system you can make omni antennas work for the LEO's most of the time but you'll probably be happier with beams and a rotor.
Regards Mark VE7AFZ
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participants (9)
-
Andrew Glasbrenner -
Bill Dzurilla -
Edward Cole -
Mark Spencer -
Raydel Abreu Espinet (CM2ESP) -
Robert Bruninga -
Samudra Haque -
Ted -
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