Thanks Bdale and Keith that gives me much more confidence to go higher! I also use an Arrow 5-element yagi. So far on flights to 8k ft I have been getting RSSI of -75 to -85dBm...provided i remember to point the yagi!
On 14 August 2012 16:07, Keith Packard <[email protected]> wrote: > Bdale Garbee <[email protected]> writes: > > > Geoff Hendrick <[email protected]> writes: > > > >> I saved this comment a while ago but cant remember where i saw it: > >> "Tests performed at Altus Metrum have shown that a 3-element yagi > antenna > >> yields good telemetry from rockets to 20 Km (65,600 feet) altitude, and > >> that a 11-element yagi antenna can receive telemetry from the > TeleMetrum to > >> around 100 Km (62 miles)" > > > > These numbers were extrapolated from signal strength measurements on > > actual flights. The highest actual flight I'm aware of so far that > > we've got in our flight database was Adrian Adamson's L single-motor > > record shot which went to something over 31k feet AGL. The recorded > > telemetry file shows good reception through apogee. I'm not sure what > > the ground station antenna was, but I'd guess a 5-element Arrow yagi. > > Yes, I used a 5-element Arrow yagi to track his flight. I tracked it > down within 60m of the ground, at about 3.2km north of the flight line; > at that point, it descended behind the RVs parked at the launch. > > One funny thing about that flight was that the RSSI didn't appear to > change much during the whole flight. During ascent, telemetry > disappeared until apogee. Adrian generally builds out of CF with the > antenna only visible after separation, so this didn't surprise me, > although I do like to be able to find the spot when a shovel is the > approved recovery tool. > > During descent, RSSI varied between -85 and -96dBm, with almost all > packets being received successfully. I'll note that Adrian is flying > version 0.9 firmware, which uses a much longer packet than we use today > (94 bytes instead of 32 bytes), which could increase the error rate by > some amount. > > Here's a plot of RSSI and height during the flight: > > > > Given that success, I'd say we'd easily receive most of the packets from > 35k', assuming a similar antenna configuration, especially the newer > 32-byte telemetry format. > > -keith > > _______________________________________________ > altusmetrum mailing list > [email protected] > http://lists.gag.com/mailman/listinfo/altusmetrum > >
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