I wanna play with it :( --Rob Sent from my phone...excuse any typos please! On Jul 2, 2014 4:12 PM, "Guan Yang" <[email protected]> wrote:
> yes, 30 dBm is 1W. > > I have an initial board based on an Atmel SAM D20 microcontroller and > RFM23BP. I've attached an RTL-SDR screenshot showing it in a CW test > mode. With simple heatsinking from the PCB through the pad on the > bottom, it barely gets hot at maximum power. > > (I'm running this board at 3.3V, which limits output to 27 dBm according > to HopeRF.) > > On Fri, May 23, 2014, at 22:37, Robert Diamond wrote: > > 30 dBm is 1W, right? > > > > > > On Fri, May 23, 2014 at 9:13 PM, David Reeves <[email protected]> > wrote: > > > > > You can certainly open the squelch on your end, but at the events I > was at > > > recently, folks were able to reliably 'kerchunk' the repeater but not > > > transmit audio - perhaps the transmitted audio just isn't often enough > > > under bad conditions to open the repeater squelches, and that we can't > > > change. > > > > > > I have been musing on the possibility of getting around the canyon > problem > > > using longer wavelengths. This paper< > http://images.rfdesign.com/files/4/0499WARNAG36.pdf> suggests > > > that a Part 15 device could theoretically easily get 10 miles at 1705 > > > kHz/100mW, at least during daylight. But it's very dependent on ground > wave > > > and noise floor, so probably it's no good for mobile stations for > audio. > > > But just maybe, with a low bandwidth digital mode, it would be enough > for > > > short texts, even if the antennas were suboptimal? I saw a video of a > guy > > > getting an urban 2 mile range with audio on medium wave AM using one > of these > > > kits <http://www.sstran.com/pages/AMT3000/overview.html>. I may get > one > > > just for experimentation purposes :) > > > > > > > > > On Fri, May 23, 2014 at 8:34 PM, Guan Yang <[email protected]> wrote: > > > > > >> On Fri, May 23, 2014, at 20:10, David Reeves wrote: > > >> > Ok, so is the reasoning here that some kind of direct FSK modulation > > >> will > > >> > suffer fewer of the propagation difficulties that we've seen with > > >> > reception > > >> > of voice/AFSK? > > >> > > >> Yes; certainly on a per-baud basis. I've found that a lot of the time > > >> under bad propagation situations you can actually hear voices if you > > >> open the squelch. Something not mediated by the FM voice thing should > be > > >> better. > > >> > > >> RFM23BP has a best case RX sensitivity of -120dBm, which is well below > > >> the noise floor at these frequencies. Of course we will have to test > it. > > >> But even if propagation is just as terrible as FM voice, it will be > > >> easier to copy a digital transmission because we can do aggressive > > >> forward error correction and easily repeat transmissions many times. > > >> > > >> It's frustrating to be able to hear that there's *some* voice without > > >> understanding the words. Also talking to people is horrible even under > > >> ideal circumstances. > > >> > > >> > I'd assume this would be simplex only, which has in fact been by > far the > > >> > most reliable over the few small-area (< 3 miles) urban nets I > attended > > >> > recently. If we could get up to a 10 mile range somehow with some > clever > > >> > digital processing, I'd think that would be very useful indeed for > us > > >> > canyon-dwellers - do you think that might be possible? > > >> > > >> We could have digipeaters. That alone would help a lot. A 2m or 70cm > FM > > >> voice repeater is a big hassle to move around and set up. With a $50 > > >> digipeater we could just plant them in various locations in the field > > >> and cross our fingers that they won't get stolen - and it won't be a > > >> huge deal if they are. > > >> _______________________________________________ > > >> Radio mailing list [email protected] > > >> https://list.hackmanhattan.com/listinfo/radio > > >> > > > > > > > > > _______________________________________________ > > > Radio mailing list [email protected] > > > https://list.hackmanhattan.com/listinfo/radio > > > > > _______________________________________________ > > Radio mailing list [email protected] > > https://list.hackmanhattan.com/listinfo/radio > > _______________________________________________ > Radio mailing list [email protected] > https://list.hackmanhattan.com/listinfo/radio >
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