[amsat-bb] Re: [aprssig] TransAtlantic Balloon on 28 MHz (signal)
Rogerkola at aol.com
Thu Feb 23 20:38:18 PST 2012
So...in several weeks you will launch?
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
> 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
> Bob, Wb4APR
> Sent via AMSAT-BB at 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
More information about the AMSAT-BB