I apologize if this topic has been covered recently, but I am asking again. I am in the middle of redoing antennas, and am looking to keep something up for the FM satellites. How well will a 1/4 wave dualband groundplane work on the satellites? I remember reading a review in QST in the past year or so about a dualband J pole,and the reviewer said he got into AO27 and AO51 just fine. What can I expect out of a 1/4 wave antenna?
73s John AA5JG
Check Bob Bruninga's (wb4apr) treatise on 19" verticals for use on 440 and 2 meter satellite frequencies (rather positive but you need a good ground plane)
Google his call and 19" ground plane or look in the archives here...
Roger WA1KAT
On 11/18/2010 8:28 PM, John Geiger wrote:
I apologize if this topic has been covered recently, but I am asking again. I am in the middle of redoing antennas, and am looking to keep something up for the FM satellites. How well will a 1/4 wave dualband groundplane work on the satellites? I remember reading a review in QST in the past year or so about a dualband J pole,and the reviewer said he got into AO27 and AO51 just fine. What can I expect out of a 1/4 wave antenna?
73s John AA5JG _______________________________________________ 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
I'm putting my shack back together after moving into my new home and have a couple of radio's I would like to sell. I'm not getting off the sats just going to upgrade a bit. I should be back on in a week or so..
1.Icom IC-910. Extras include the 1200 mHz option, one AF DSP chip for the RX, power cord, and new complete faceplate not yet installed. $1000 or best offer.
2. Kenwood TH D7G. includes 2 batteries, drop in charger, and speaker hand mic. While parts were available I replaced all the rubber and front plastic on radio, thus it works, and also looks like new. $250 or best offer.
I have the manuals for the D7, and 910. No original shipping box for the 910. Price includes shipping CONUS. Reason I'm selling is I'm going to upgrade to an Icom 9100, and the new Kenwood replacement for the D7.
I will also donate 10% net of the sale to AMSATNA.
73 Jeff kb2m
The Kenwood is still for sale. I'm still unpacking from the move and found a GPS and cable that I will add to the deal. The 910 has been sold. Thanks for all the interest.
73 Jeff kb2m
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Jeff KB2M Sent: Friday, November 19, 2010 6:41 AM To: 'Amsat-Bb@Amsat. Org' Subject: [amsat-bb] sat radios for sale
I'm putting my shack back together after moving into my new home and have a couple of radio's I would like to sell. I'm not getting off the sats just going to upgrade a bit. I should be back on in a week or so..
1.Icom IC-910. Extras include the 1200 mHz option, one AF DSP chip for the RX, power cord, and new complete faceplate not yet installed. $1000 or best offer.
2. Kenwood TH D7G. includes 2 batteries, drop in charger, and speaker hand mic. While parts were available I replaced all the rubber and front plastic on radio, thus it works, and also looks like new. $250 or best offer.
I have the manuals for the D7, and 910. No original shipping box for the 910. Price includes shipping CONUS. Reason I'm selling is I'm going to upgrade to an Icom 9100, and the new Kenwood replacement for the D7.
I will also donate 10% net of the sale to AMSATNA.
73 Jeff kb2m
_______________________________________________ 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
On Thu, Nov 18, 2010 at 9:28 PM, John Geiger aa5jg@fidmail.com wrote:
I apologize if this topic has been covered recently, but I am asking again. I am in the middle of redoing antennas, and am looking to keep something up for the FM satellites. How well will a 1/4 wave dualband groundplane work on the satellites? I remember reading a review in QST in the past year or so about a dualband J pole,and the reviewer said he got into AO27 and AO51 just fine. What can I expect out of a 1/4 wave antenna?
73s John AA5JG
Hi, John --
If you picture the pattern of a typical 1/4 wave antenna, you will recall that the it looks a bit like a half-bagel lying face down on the kitchen counter. This is super for terrestrial work, where we want to have as much power as possible going out to the horizon, because the other, earth-bound stations are to be found at that low elevation. But such an antenna improves its power on the horizon by 'stealing' some from higher elevations, and once you think about transmitting to or receiving from a station up 20 degrees or more, say, you'll find that you're working with much less power. And once you're, say, 70 degrees from the counter-top, well, with an ideal 1/4 wave, you're putting out no power (and receiving none) whatsoever. (In reality, its not that bad, but its pretty darn bad.)
For this reason, a standard 1/4 wave (or J-pole) isn't ideal for satellite work. It will certainly work, especially in the elevation band where the path losses (which decrease with elevation) and losses due to your antenna pattern produce a maximum signal. It's great fun to listen for this effect, and a bit easier to observe with a CW signal and s-meter. (You can treat a FM bird's signal as an FM signal just by switching modes, of course.)
What would be an ideal shape for our 'omnidirectional' satellite antenna? Let's have a muffin instead of a bagel, lop its top off and place that on the counter instead of the bagel. Now we have increased power at the low elevations, but still some power at the higher ones. Note, we don't want a situation where the power is all going straight up, because satellites spend a good deal of time in the low angles (depending on where you are). We just want to 'fill in' the bits that we lose from our bagel pattern.
There are many designs that aim to provide something like this muffin pattern. You can make your vertical longer than 5/8 wavelength (the 19" at 440, e.g.); you can tilt the 1/4 wave vertical at around 20 deg. from perpendicular to its ground plane; you can use lindenblad arrangements to circularize and redistribute. I have a 2m qadrifilar helix antenna that does its job nicely.
One terribly important point on 70cm is that you have a low noise preamp connected to the antenna on the mast, not in your shack. I have a $5 70cm 1/4 wave groundplane that I made out of a female N-connector. I would much, much rather use it with my ARR preamp than a 8 element yagi without the preamp. Way more fun. The reason for this with omni antennas is that we are having to distribute all the 'receiving power' over all the elevation angles, as well as the 360 degrees of azimuth. In other words, your muffin has to be smaller in diameter than your bagel half, because both have to have the same total volume.
Finally, your question suggests that simpler antennas, like 1/4 wave groundplanes, are not necessarily easy to use on SSB/CW birds. I find the contrary, especially on CW. FM satellites are easier because they don't require as frequent tuning due to doppler shift, and because many hams already have the equipment needed to operate them. But they aren't 'easier' in the sense that their signals are easier to hear with simple equipment. Heck, with any sort of antenna and an low-noise preamp you'll hear the CW beacon of HO-68 from horizon to horizon.
I hope you will forgive me if this reply was aimed at the wrong level, and I wish you all the best in your satellite station building.
73, Bruce VE9QRP
... a typical 1/4 wave antenna... is super for terrestrial work, where we want to have as much power as possible going out to the horizon... but... from a station up 20 degrees or more, say, you'll find that you're working with much less ... And, say, 70 degrees... with an ideal 1/4 wave, you're putting out no power (and receiving none) (In reality, its not that bad, but its pretty darn bad.)
I think the essence of what is being said is relatively correct individually, but on closer inspection I think this is mixing apples and oranges. What is said is true for *gain* omni's, but not really true for the 1/4 wave vertical. In fact, the 1/4 wave is about the best and simplest omni antenna for satellites. Please see the detail explanation
The argument being presented above *does* apply to a *gain* verticla omni. Yes, that is NOT good for satellite work because it does as stated, concentrates gain on the horizon and drastically falls off at higher elevation. So that is why we say "omnis" are not good for satellites. Because almost everyone uses a *gain* omni.
But the 1/4 ground plane antenna does not concentrate all of its energy on the horizon and is why most people will not use it for terrestrial work because too much of it goes out at higher elevations. And even though it does drop off by more than 10 dB at high angles above 60 degrees, one has to remember that the satellite is 10 dB closer at that high angle! So it still works great. AND the amount of time that a LEO satelite is above even 50 degrees is only 2% of all the access time. Nothing at all to worry about.
See the plot of gain on the above web page. It shows that a 1/4 vertical has nearly constant gain for a satellite from about 10 degrees up to over 70 degrees because of this range-gain. Of course below 10 degrees the satellite is as much as 3 db further away and hence weaker and most satellite link budgets were not designed to operate with such 0 dB gain omnis AT the horizon.
So, the 1/4 vertical is very hard to beat for a simple omni satellite antenna. And by the same rationale, the terrestrial gain omni is NOT. SO watch out for apples and oranges comparisons...
Bob, WB4APR
What would be an ideal shape for our 'omnidirectional'
satellite
antenna? Let's have a muffin instead of a bagel, lop its top
off and
place that on the counter instead of the bagel. Now we have
increased
power at the low elevations, but still some power at the
higher ones.
Note, we don't want a situation where the power is all going
straight
up, because satellites spend a good deal of time in the low
angles
(depending on where you are). We just want to 'fill in' the
bits that
we lose from our bagel pattern.
There are many designs that aim to provide something like this
muffin
pattern. You can make your vertical longer than 5/8 wavelength
(the
19" at 440, e.g.); you can tilt the 1/4 wave vertical at
around 20
deg. from perpendicular to its ground plane; you can use
lindenblad
arrangements to circularize and redistribute. I have a 2m
qadrifilar
helix antenna that does its job nicely.
One terribly important point on 70cm is that you have a low
noise
preamp connected to the antenna on the mast, not in your
shack. I have
a $5 70cm 1/4 wave groundplane that I made out of a female N-connector. I would much, much rather use it with my ARR
preamp than
a 8 element yagi without the preamp. Way more fun. The reason
for this
with omni antennas is that we are having to distribute all the 'receiving power' over all the elevation angles, as well as
the 360
degrees of azimuth. In other words, your muffin has to be
smaller in
diameter than your bagel half, because both have to have the
same
total volume.
Finally, your question suggests that simpler antennas, like
1/4 wave
groundplanes, are not necessarily easy to use on SSB/CW birds.
I find
the contrary, especially on CW. FM satellites are easier
because they
don't require as frequent tuning due to doppler shift, and
because
many hams already have the equipment needed to operate them.
But they
aren't 'easier' in the sense that their signals are easier to
hear
with simple equipment. Heck, with any sort of antenna and an
low-noise
preamp you'll hear the CW beacon of HO-68 from horizon to
horizon.
I hope you will forgive me if this reply was aimed at the
wrong level,
and I wish you all the best in your satellite station
building.
73, Bruce VE9QRP -- http://ve9qrp.blogspot.com
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:
At 09:10 AM 11/19/2010, Robert Bruninga wrote:
... a typical 1/4 wave antenna... is super for terrestrial work, where we want to have as much power as possible going out to the horizon... but... from a station up 20 degrees or more, say, you'll find that you're working with much less ... And, say, 70 degrees... with an ideal 1/4 wave, you're putting out no power (and receiving none) (In reality, its not that bad, but its pretty darn bad.)
I think the essence of what is being said is relatively correct individually, but on closer inspection I think this is mixing apples and oranges. What is said is true for *gain* omni's, but not really true for the 1/4 wave vertical. In fact, the 1/4 wave is about the best and simplest omni antenna for satellites. Please see the detail explanation
The argument being presented above *does* apply to a *gain* verticla omni. Yes, that is NOT good for satellite work because it does as stated, concentrates gain on the horizon and drastically falls off at higher elevation. So that is why we say "omnis" are not good for satellites. Because almost everyone uses a *gain* omni.
But the 1/4 ground plane antenna does not concentrate all of its energy on the horizon and is why most people will not use it for terrestrial work because too much of it goes out at higher elevations. And even though it does drop off by more than 10 dB at high angles above 60 degrees, one has to remember that the satellite is 10 dB closer at that high angle! So it still works great. AND the amount of time that a LEO satelite is above even 50 degrees is only 2% of all the access time. Nothing at all to worry about.
See the plot of gain on the above web page. It shows that a 1/4 vertical has nearly constant gain for a satellite from about 10 degrees up to over 70 degrees because of this range-gain. Of course below 10 degrees the satellite is as much as 3 db further away and hence weaker and most satellite link budgets were not designed to operate with such 0 dB gain omnis AT the horizon.
So, the 1/4 vertical is very hard to beat for a simple omni satellite antenna. And by the same rationale, the terrestrial gain omni is NOT. SO watch out for apples and oranges comparisons...
Bob, WB4APR
Just a note that I used a 19-inch mag-mount whip on a square sheet of steel sheetmetal on my roof to copy telemetry on AO-51 when it was first launched. This was UHF so the whip was working as a 3/4 wave vertical. The important part of that is that the 432-MHz preamp MUST be installed very near the antenna (I had about 10-foot of RG-58 as the standard cable for the magnetic base).
If you are planning to use it for up and down link then you need a diplexer to separate the two frequencies and isolate the preamp from the 2m transmit signal. Since typically all you need is about 5w that is not difficult.
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep dubususa@hotmail.com ====================================== *temp not in service
Thank you, Bob, for clarifying this. The original letter made mention of several types of antennas, including 1/4wave dualband and jpole, both of which are, in your terms below, gain omnis at 440. (Jpole being a 1/2wave antenna, e.g.) I first wrote the letter with these distinctions kept intact, but then, in an attempt to keep things simple, used 1/4 throughout, which meant that the claims about 1/4 elevation patterns were not accurate. However they would be accurate for the "1/4 wave vertical" that John originally mentioned, at least on 70cm.
So for the purpose of practical advice, I hope we can agree that: a) a *true* 1/4 wave gp vertical makes a fine and inexpensive vertical omni for satellite work. But this means that the 70cm's vertical element should be around 18cm long. If it's longer, you're likely getting gain, and that ain't good in this circumstance. b) using a gain omni such as a jpole (or, likely, a multiband vertical on 70cm) will produce the effects described in my letter below c) with such an vertical you will occasionally suffer drop-outs at very high elevation d) I could have been clearer :-)
73, Bruce VE9QRP
On Fri, Nov 19, 2010 at 2:10 PM, Robert Bruninga bruninga@usna.edu wrote:
... a typical 1/4 wave antenna... is super for terrestrial work, where we want to have as much power as possible going out to the horizon... but... from a station up 20 degrees or more, say, you'll find that you're working with much less ... And, say, 70 degrees... with an ideal 1/4 wave, you're putting out no power (and receiving none) (In reality, its not that bad, but its pretty darn bad.)
I think the essence of what is being said is relatively correct individually, but on closer inspection I think this is mixing apples and oranges. What is said is true for *gain* omni's, but not really true for the 1/4 wave vertical. In fact, the 1/4 wave is about the best and simplest omni antenna for satellites. Please see the detail explanation
The argument being presented above *does* apply to a *gain* verticla omni. Yes, that is NOT good for satellite work because it does as stated, concentrates gain on the horizon and drastically falls off at higher elevation. So that is why we say "omnis" are not good for satellites. Because almost everyone uses a *gain* omni.
But the 1/4 ground plane antenna does not concentrate all of its energy on the horizon and is why most people will not use it for terrestrial work because too much of it goes out at higher elevations. And even though it does drop off by more than 10 dB at high angles above 60 degrees, one has to remember that the satellite is 10 dB closer at that high angle! So it still works great. AND the amount of time that a LEO satelite is above even 50 degrees is only 2% of all the access time. Nothing at all to worry about.
See the plot of gain on the above web page. It shows that a 1/4 vertical has nearly constant gain for a satellite from about 10 degrees up to over 70 degrees because of this range-gain. Of course below 10 degrees the satellite is as much as 3 db further away and hence weaker and most satellite link budgets were not designed to operate with such 0 dB gain omnis AT the horizon.
So, the 1/4 vertical is very hard to beat for a simple omni satellite antenna. And by the same rationale, the terrestrial gain omni is NOT. SO watch out for apples and oranges comparisons...
Bob, WB4APR
What would be an ideal shape for our 'omnidirectional'
satellite
antenna? Let's have a muffin instead of a bagel, lop its top
off and
place that on the counter instead of the bagel. Now we have
increased
power at the low elevations, but still some power at the
higher ones.
Note, we don't want a situation where the power is all going
straight
up, because satellites spend a good deal of time in the low
angles
(depending on where you are). We just want to 'fill in' the
bits that
we lose from our bagel pattern.
There are many designs that aim to provide something like this
muffin
pattern. You can make your vertical longer than 5/8 wavelength
(the
19" at 440, e.g.); you can tilt the 1/4 wave vertical at
around 20
deg. from perpendicular to its ground plane; you can use
lindenblad
arrangements to circularize and redistribute. I have a 2m
qadrifilar
helix antenna that does its job nicely.
One terribly important point on 70cm is that you have a low
noise
preamp connected to the antenna on the mast, not in your
shack. I have
a $5 70cm 1/4 wave groundplane that I made out of a female N-connector. I would much, much rather use it with my ARR
preamp than
a 8 element yagi without the preamp. Way more fun. The reason
for this
with omni antennas is that we are having to distribute all the 'receiving power' over all the elevation angles, as well as
the 360
degrees of azimuth. In other words, your muffin has to be
smaller in
diameter than your bagel half, because both have to have the
same
total volume.
Finally, your question suggests that simpler antennas, like
1/4 wave
groundplanes, are not necessarily easy to use on SSB/CW birds.
I find
the contrary, especially on CW. FM satellites are easier
because they
don't require as frequent tuning due to doppler shift, and
because
many hams already have the equipment needed to operate them.
But they
aren't 'easier' in the sense that their signals are easier to
hear
with simple equipment. Heck, with any sort of antenna and an
low-noise
preamp you'll hear the CW beacon of HO-68 from horizon to
horizon.
I hope you will forgive me if this reply was aimed at the
wrong level,
and I wish you all the best in your satellite station
building.
73, Bruce VE9QRP -- http://ve9qrp.blogspot.com
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:
Thank you, Bob, for clarifying this. The original letter made
mention
of several types of antennas, including 1/4wave dualband and
jpole,
both of which are, in your terms below, gain omnis at 440.
Actually, although a true 1/4 wave over an infinite ground plane does have 3 dB gain over a dipole, very few people use an infinite ground plane and so I consider the 1/4 "ground plane" (with 1/4 radials) and 1/2 wave vertical dipoles and J-poles all to be non gain omnis. They basically have 0 dBd gain, and my comments are pretty much still valid I think. So I think a J-pole also makes a pretty good omni antenna for satellites. (Better than all other terrestrial "gain" antennnas.
When I refer to terrestrial omni "Gain" antennas, I am talking about the 5/8ths wave (which has a complete null at only 15 degrees above the horizon) and other larger terrestrial gain antennas up to 6 and 9 dBd gain.
Hope that clarifies it. Bob, WB4APR
(Jpole
being a 1/2wave antenna, e.g.) I first wrote the letter with
these
distinctions kept intact, but then, in an attempt to keep
things
simple, used 1/4 throughout, which meant that the claims about
1/4
elevation patterns were not accurate. However they would be
accurate
for the "1/4 wave vertical" that John originally mentioned, at
least
on 70cm.
So for the purpose of practical advice, I hope we can agree
that:
a) a *true* 1/4 wave gp vertical makes a fine and inexpensive
vertical
omni for satellite work. But this means that the 70cm's
vertical
element should be around 18cm long. If it's longer, you're
likely
getting gain, and that ain't good in this circumstance. b) using a gain omni such as a jpole (or, likely, a multiband
vertical
on 70cm) will produce the effects described in my letter below c) with such an vertical you will occasionally suffer
drop-outs at
very high elevation d) I could have been clearer :-)
73, Bruce VE9QRP
On Fri, Nov 19, 2010 at 2:10 PM, Robert Bruninga bruninga@usna.edu wrote:
... a typical 1/4 wave antenna... is super for terrestrial work, where we want to have as much power as possible going out to the horizon... but... from a station up 20 degrees or more, say, you'll find that you're working with much less ... And, say, 70 degrees... with an ideal 1/4 wave, you're putting out no power (and receiving none) (In reality, its not that bad, but its pretty darn bad.)
I think the essence of what is being said is relatively
correct
individually, but on closer inspection I think this is
mixing
apples and oranges. What is said is true for *gain* omni's,
but
not really true for the 1/4 wave vertical. In fact, the 1/4 wave is about the best and simplest omni antenna for
satellites.
Please see the detail explanation
The argument being presented above *does* apply to a *gain* verticla omni. Yes, that is NOT good for satellite work
because
it does as stated, concentrates gain on the horizon and drastically falls off at higher elevation. So that is why
we
say "omnis" are not good for satellites. Because almost everyone uses a *gain* omni.
But the 1/4 ground plane antenna does not concentrate all of
its
energy on the horizon and is why most people will not use it
for
terrestrial work because too much of it goes out at higher elevations. And even though it does drop off by more than
10 dB
at high angles above 60 degrees, one has to remember that
the
satellite is 10 dB closer at that high angle! So it still
works
great. AND the amount of time that a LEO satelite is above
even
50 degrees is only 2% of all the access time. Nothing at
all to
worry about.
See the plot of gain on the above web page. It shows that a
1/4
vertical has nearly constant gain for a satellite from about
10
degrees up to over 70 degrees because of this range-gain.
Of
course below 10 degrees the satellite is as much as 3 db
further
away and hence weaker and most satellite link budgets were
not
designed to operate with such 0 dB gain omnis AT the
horizon.
So, the 1/4 vertical is very hard to beat for a simple omni satellite antenna. And by the same rationale, the
terrestrial
gain omni is NOT. SO watch out for apples and oranges comparisons...
Bob, WB4APR
What would be an ideal shape for our 'omnidirectional'
satellite
antenna? Let's have a muffin instead of a bagel, lop its
top
off and
place that on the counter instead of the bagel. Now we have
increased
power at the low elevations, but still some power at the
higher ones.
Note, we don't want a situation where the power is all
going
straight
up, because satellites spend a good deal of time in the low
angles
(depending on where you are). We just want to 'fill in' the
bits that
we lose from our bagel pattern.
There are many designs that aim to provide something like
this
muffin
pattern. You can make your vertical longer than 5/8
wavelength
(the
19" at 440, e.g.); you can tilt the 1/4 wave vertical at
around 20
deg. from perpendicular to its ground plane; you can use
lindenblad
arrangements to circularize and redistribute. I have a 2m
qadrifilar
helix antenna that does its job nicely.
One terribly important point on 70cm is that you have a low
noise
preamp connected to the antenna on the mast, not in your
shack. I have
a $5 70cm 1/4 wave groundplane that I made out of a female N-connector. I would much, much rather use it with my ARR
preamp than
a 8 element yagi without the preamp. Way more fun. The
reason
for this
with omni antennas is that we are having to distribute all
the
'receiving power' over all the elevation angles, as well as
the 360
degrees of azimuth. In other words, your muffin has to be
smaller in
diameter than your bagel half, because both have to have
the
same
total volume.
Finally, your question suggests that simpler antennas, like
1/4 wave
groundplanes, are not necessarily easy to use on SSB/CW
birds.
I find
the contrary, especially on CW. FM satellites are easier
because they
don't require as frequent tuning due to doppler shift, and
because
many hams already have the equipment needed to operate
them.
But they
aren't 'easier' in the sense that their signals are easier
to
hear
with simple equipment. Heck, with any sort of antenna and
an
low-noise
preamp you'll hear the CW beacon of HO-68 from horizon to
horizon.
I hope you will forgive me if this reply was aimed at the
wrong level,
and I wish you all the best in your satellite station
building.
73, Bruce VE9QRP -- http://ve9qrp.blogspot.com
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:
participants (6)
-
Bruce Robertson -
Edward R. Cole -
Jeff KB2M -
John Geiger -
Robert Bruninga -
Roger Kolakowski