For various reasons I only have one functional board right now. I'll try to assemble a few more tomorrow so we can test range, frequency deviation and data rates. I believe the default is 20 kHz deviation, which is not very friendly, and I want to see if 5 kHz works. That should give a total bandwidth of roughly what an FM voice channel occupies.
I'm trying to demodulate in GNU Radio but it's a fucking nightmare to figure out. On Jul 2, 2014, at 16:58, Zachary Giles <[email protected]> wrote: > *pant pant* > > On Wed, Jul 2, 2014 at 4:51 PM, Robby O'Connor <[email protected]> > wrote: >> 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 >> >> >> _______________________________________________ >> Radio mailing list [email protected] >> https://list.hackmanhattan.com/listinfo/radio > > > > -- > Zach Giles > [email protected] > _______________________________________________ > Radio mailing list [email protected] > https://list.hackmanhattan.com/listinfo/radio _______________________________________________ Radio mailing list [email protected] https://list.hackmanhattan.com/listinfo/radio
