TransAtlantic Balloon on 28 MHz ?
Do you have a 10 meter (28 MHz) vertically polarized beam?
We are working on a 28 MHz transatlantic Balloon with a CW transmitter on 10m using (of course) a vertical dipole.
It will have no GPS, so tracking will be entirely by beam headings and some signal-strength assessment.
Just wondering if anyone has a vertical beam.
A horizontal beam will be useless for direction finding. All it will do is point to whatever is reflecting the energy into the strongest horizontal component...
Hummh... Bob, WB4APR
Bob says "Just wondering if anyone has a vertical beam. A horizontal beam will be useless for direction finding. All it will do is point to whatever is reflecting the energy into the strongest horizontal component..."
That is only true when receiving the signal via direct line of sight propagation.
Once the signal is over the horizon, and is using the ionosphere to propagate the signal, the reflected signal can and does come back down at any polarization.
Matter of fact in minutes it can "Rotate" from vertical to horizontal and anywhere in between. or even faster rotation. QSB is mostly caused by this polarity rotation of the signal.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 2/15/2012 11:18 PM, Bob Bruninga wrote:
Just wondering if anyone has a vertical beam.
A horizontal beam will be useless for direction finding. All it will do is point to whatever is reflecting the energy into the strongest horizontal component...
Just wondering if anyone has a vertical beam. A horizontal beam [for this vertical balloon signal] will be useless for direction finding....
That is only true when receiving the signal via direct line of sight propagation.
The transmitter is only 10 milliwatts, so we only expect line-of-sight contact. So that is why I was assuming we'd need a reasonable polarization match. But who knows... maybe we will get some good OTH signals.? The altitude will not be super high though, (like in the ionosphere)..
Bob, WB4APR
CB uses vertical beams...the difficulty is that they have to have a non metallic mounting pole extending into the beam or be end mounted (think torque)
With enough planning I'm sure enough hams could chase something up and use empty Stationmaster radomes, fiberglass poles or even schedule 80 pipe to get something up.
Roger WA1KAT
On 2/16/2012 12:18 AM, Bob Bruninga wrote:
Do you have a 10 meter (28 MHz) vertically polarized beam?
We are working on a 28 MHz transatlantic Balloon with a CW transmitter on 10m using (of course) a vertical dipole.
It will have no GPS, so tracking will be entirely by beam headings and some signal-strength assessment.
Just wondering if anyone has a vertical beam.
A horizontal beam will be useless for direction finding. All it will do is point to whatever is reflecting the energy into the strongest horizontal component...
Hummh... Bob, WB4APR _______________________________________________ Sent via [email protected]. 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, 2/16/12, Roger [email protected] wrote:
CB uses vertical beams...the difficulty is that they have to have a non metallic mounting pole extending into the beam or be end mounted (think torque)
The mounting pole may contribute some capacitive or inductive loading effects on the elements adjacent to it, but a smart antenna designer can modify the antenna's element lengths to compensate for these effects.
The pole itself will have a negligible effect on antenna performance, unless it happens to be resonant (or very close to resonant) at the operating frequency. Otherwise, it's essentially transparent.
On 2/16/2012 12:18 AM, Bob Bruninga wrote:
Just wondering if anyone has a vertical beam.
If the signal is strong enough (and/or the receiver sensitive enough), an electrically small loop antenna can be used for 28 MHz radio direction finding purposes.
A vertically oriented loop will respond to vertically polarized RF. (In reality, it's responding to the horizontally polarized H-field).
The ARRL Handbooks and Antenna Books have carried designs regarding 28 MHz RDF antenna for many decades.
73, de John, KD2BD
We are working on a 28 MHz transatlantic Balloon with a CW transmitter on 10m using (of course) a vertical dipole. Do you have a 10 meter (28 MHz) vertically polarized beam?
The response was as expected. No one has. Therefore we will accept horizontal beam headings. Also we will ask for signal strength reports including a reference signal level with and without antenna.
We just did a far-field test line-of-sight over 0.88 miles and had a 75 dB Signal margin (vertical to vertical). This is above about 21 dB of antenna noise. This implies about a line-of-sight range of over 8000 km. So it looks like signal strength should be no problem...
The FT-817 S meter was tested to reveal a ridiculous range of from 1 to 20 dB per S unit. The range comparison is not much better as shown here...
-43 dBm S+++= .25 km -55 dBm S++ = 0.4 km -63 dBm S+ = 2.5 km -73 dBm S9 = 8 km At altitude even overhead -93 dBm S8 = 82 km -97 dBm S7 = 100 km -98 dBm S6 = 115 km -99 dBm S5 = 130 km -100 dBm S4 = 184 km -101 dBm S3 = 206 km -102 dBm S2 = 231 km -103 dBm S1 = 258 km Min signal = 8000 km
So hearing it won't be a problem, but guessing where it is will be a challenge.
We are currently waiting on the Helium and the balloons. Total mass is about double the weight of a 9v battery.
Launch probably a few weeks away yet. Oh, and Hydrogen (H2) which is 50% lighter than Helium only gains about 5%. The way to think about it is not to compare He to H2 (2-to-1) but to compare Air-to-Helium (10-to-1) and air-to-H2 (10-to.5) so the difference in lifting capacity is only 0.5 out of 10 or about 5%. Now it makes sense.
The real advantage of H2 is you can make your own. He is a limited natural resource that we are running out of even faster than we are running out of dead dinosaurs. And it takes millions of years of radioactive decay to make more.
Bob, Wb4APR
So...in several weeks you will launch?
Roger WA1KAT
On 2/23/2012 3:57 PM, Bob Bruninga wrote:
We are working on a 28 MHz transatlantic Balloon with a CW transmitter on 10m using (of course) a vertical dipole. Do you have a 10 meter (28 MHz) vertically polarized beam?
The response was as expected. No one has. Therefore we will accept horizontal beam headings. Also we will ask for signal strength reports including a reference signal level with and without antenna.
We just did a far-field test line-of-sight over 0.88 miles and had a 75 dB Signal margin (vertical to vertical). This is above about 21 dB of antenna noise. This implies about a line-of-sight range of over 8000 km. So it looks like signal strength should be no problem...
The FT-817 S meter was tested to reveal a ridiculous range of from 1 to 20 dB per S unit. The range comparison is not much better as shown here...
-43 dBm S+++= .25 km -55 dBm S++ = 0.4 km -63 dBm S+ = 2.5 km -73 dBm S9 = 8 km At altitude even overhead -93 dBm S8 = 82 km -97 dBm S7 = 100 km -98 dBm S6 = 115 km -99 dBm S5 = 130 km -100 dBm S4 = 184 km -101 dBm S3 = 206 km -102 dBm S2 = 231 km -103 dBm S1 = 258 km Min signal = 8000 km
So hearing it won't be a problem, but guessing where it is will be a challenge.
We are currently waiting on the Helium and the balloons. Total mass is about double the weight of a 9v battery.
Launch probably a few weeks away yet. Oh, and Hydrogen (H2) which is 50% lighter than Helium only gains about 5%. The way to think about it is not to compare He to H2 (2-to-1) but to compare Air-to-Helium (10-to-1) and air-to-H2 (10-to.5) so the difference in lifting capacity is only 0.5 out of 10 or about 5%. Now it makes sense.
The real advantage of H2 is you can make your own. He is a limited natural resource that we are running out of even faster than we are running out of dead dinosaurs. And it takes millions of years of radioactive decay to make more.
Bob, Wb4APR
Sent via [email protected]. 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
Line of sight may be in theory 8000 miles, and possible in satellites, but in this ballooning you will never ever get this because the Earth gets in the way. You may at best get a line of sight of 400 to 500 miles at the most.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 2/23/2012 10:38 PM, Roger wrote:
So...in several weeks you will launch?
Roger WA1KAT
On 2/23/2012 3:57 PM, Bob Bruninga wrote:
We are working on a 28 MHz transatlantic Balloon with a CW transmitter on 10m using (of course) a vertical dipole. Do you have a 10 meter (28 MHz) vertically polarized beam?
The response was as expected. No one has. Therefore we will accept horizontal beam headings. Also we will ask for signal strength reports including a reference signal level with and without antenna.
We just did a far-field test line-of-sight over 0.88 miles and had a 75 dB Signal margin (vertical to vertical). This is above about 21 dB of antenna noise. This implies about a line-of-sight range of over 8000 km. So it looks like signal strength should be no problem...
The FT-817 S meter was tested to reveal a ridiculous range of from 1 to 20 dB per S unit. The range comparison is not much better as shown here...
-43 dBm S+++= .25 km -55 dBm S++ = 0.4 km -63 dBm S+ = 2.5 km -73 dBm S9 = 8 km At altitude even overhead -93 dBm S8 = 82 km -97 dBm S7 = 100 km -98 dBm S6 = 115 km -99 dBm S5 = 130 km -100 dBm S4 = 184 km -101 dBm S3 = 206 km -102 dBm S2 = 231 km -103 dBm S1 = 258 km Min signal = 8000 km
So hearing it won't be a problem, but guessing where it is will be a challenge.
We are currently waiting on the Helium and the balloons. Total mass is about double the weight of a 9v battery.
Launch probably a few weeks away yet. Oh, and Hydrogen (H2) which is 50% lighter than Helium only gains about 5%. The way to think about it is not to compare He to H2 (2-to-1) but to compare Air-to-Helium (10-to-1) and air-to-H2 (10-to.5) so the difference in lifting capacity is only 0.5 out of 10 or about 5%. Now it makes sense.
The real advantage of H2 is you can make your own. He is a limited natural resource that we are running out of even faster than we are running out of dead dinosaurs. And it takes millions of years of radioactive decay to make more.
Bob, Wb4APR
Sent via [email protected]. 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 [email protected]. 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 (4)
-
Bob Bruninga -
Joe -
John Magliacane -
Roger