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
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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