The whole premise is I'm thinking the specs are BS. Not only are they in nice round number, but they scale perfectly linearly and claim within 1-2 dB of the same sensitivity as arguably the most advanced radio hardware design on the market.
On Sep 21, 2017 1:24 PM, "Chris Gustaf" <[email protected]> wrote: > Chuck is right. The system noise figure is a combination of amplifier > gains, amplifier noise figures, and filter losses, so best just to refer to > the manufacturer specs for comparison. The sensitivity specs will include > the effect of noise figure, in case the noise figure is not given. > > On Thu, Sep 21, 2017 at 11:15 AM, Chuck McCown <[email protected]> wrote: > >> I would add front end filter loss adds directly to noise figure which >> affects sensitivity. >> >> *From:* Chris Gustaf >> *Sent:* Thursday, September 21, 2017 12:11 PM >> *To:* [email protected] >> *Subject:* Re: [AFMUG] radio specifications... HOW? >> >> You are correct that wider front end filters give up masking and >> rejection of out of band interferers, but the intermediate frequency (IF) >> and baseband filters are what determines RX sensitivity. >> >> In the case you outlined, if the channel width was say 56 MHz for both >> QAMs and the tuning range was 200 MHz or 1000 MHz, there would be no real >> difference in sensitivity for the same modulation/channel width. The 1000 >> MHz tuning unit range may be more susceptible to interference outside 200 >> MHz filter range is all- this depends on other radio design elements. >> >> You can try asking the supplier for a Threshold to Interference (T/I) >> curve, which will show how strong a like signal at various frequencies will >> cause BERs on the radio. Most licensed radio manufacturers should have >> this data. >> >> >> Chris >> >> >> >> >> On Thu, Sep 21, 2017 at 10:22 AM, Josh Reynolds <[email protected]> >> wrote: >> >>> It is my understanding that the larger the operational range of the >>> radio, it is using vastly different filters to accommodate that range. >>> These filters give up masking performance outside of the channel mask for >>> an increase in range. >>> >>> Those wider range filters end up costing the radio *selectivity*. >>> >>> If this is incorrect, please say so. >>> >>> On Sep 21, 2017 12:07 PM, "Chris Gustaf" <[email protected]> wrote: >>> >>>> In general for each increase in modulation level it requires about 3 dB >>>> more SNR (see below), and for each doubling of channel bandwidth you lose 3 >>>> dB sensitivity. >>>> >>>> SNR Requirements for Trango and others: >>>> >>>> QAM/SNR (dB) >>>> 256QAM/26.1 >>>> 512QAM/29 >>>> 1024QAM/32.5 >>>> 2048QAM/35.8 >>>> 4096QAM/40 >>>> >>>> The frequency tuning range of the radio has nothing to do with the >>>> sensitivity. >>>> >>>> So 4096QAM requires about 14 dB More SNR than 256 QAM for the same >>>> channel size, but since in this case it uses a smaller channel bandwidth it >>>> has a lower noise floor by 7 dB as Forrest stated. The 4096 QAM radio will >>>> require a 7 dB stronger signal to hold its modulation.. >>>> >>>> Hope this helps >>>> Chris >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> On Thu, Sep 21, 2017 at 5:24 AM, Josh Reynolds <[email protected]> >>>> wrote: >>>> >>>>> I would rather not name the vendors at this time. >>>>> >>>>> On Sep 21, 2017 2:30 AM, "Mitch Koep" <[email protected]> wrote: >>>>> >>>>>> Josh >>>>>> >>>>>> Will you shall the radio info? >>>>>> >>>>>> Mitch >>>>>> >>>>>> On 9/21/2017 12:57 AM, Josh Reynolds wrote: >>>>>> >>>>>> The frequency agility between the radios is 800 mhz. Vastly >>>>>> different radio filters. >>>>>> Both are capable of similar channel bandwidths. >>>>>> This is all done at MCS0 / QPSK >>>>>> >>>>>> I'm comparing, basically, their sensitivity and selectivity. The >>>>>> radio that is frequency capable of 200mhz is also capable of hitting >>>>>> 4096QAM, while the radio capable of operating in a 1GHz range of >>>>>> frequencies is 256QAM capable. >>>>>> >>>>>> Basically, it's (the 256QAM radio) sensitivity at the same modulation >>>>>> and the same power is wayyyyyy closer than I would expect it should be - >>>>>> vastly different, and far cheaper components. TL;DR: I'm calling BS on >>>>>> the >>>>>> data sheet :) >>>>>> >>>>>> On Thu, Sep 21, 2017 at 12:23 AM, Forrest Christian (List Account) < >>>>>> [email protected]> wrote: >>>>>> >>>>>>> Can you give specific examples? Having a hard time understanding >>>>>>> for sure the exact specs you're comparing. >>>>>>> >>>>>>> In relation to the thermal noise floor: just reducing from 1000mz >>>>>>> to 200mhz will gain you ~7db of noise floor. But usually that's in a >>>>>>> channel, not in the entire 'frequency agility' area. Maybe they aren't >>>>>>> all >>>>>>> that selective within the 1Ghz bandwidth. >>>>>>> >>>>>>> I've never been able to find a chart of theoretical required s/n >>>>>>> ratio for each of the QAM's so I can't comment on how much difference >>>>>>> there >>>>>>> is supposed to be - after all, with everything else being the same >>>>>>> (channel, modulation, power, etc), 256QAM should definitely require a >>>>>>> lower >>>>>>> signal strength than a 4096QAM radio. They definitely shouldn't be >>>>>>> the >>>>>>> same with the same channel width, unless one radio is noisier or more >>>>>>> susceptible to noise. >>>>>>> >>>>>>> And sensitivity should just be about the receiver, not the >>>>>>> transmitter. >>>>>>> >>>>>>> On Wed, Sep 20, 2017 at 9:20 PM, Josh Reynolds <[email protected] >>>>>>> > wrote: >>>>>>> >>>>>>>> Can someone smarter than I fill me in on something? I'm comparing >>>>>>>> some >>>>>>>> radios here (no names...) >>>>>>>> >>>>>>>> One radio is 256 QAM, with a 1000mhz operating range >>>>>>>> >>>>>>>> Another one is 4096 QAM, with a 200mhz operating range >>>>>>>> >>>>>>>> Can you explain to me how the sensitivity on the 256QAM radio, at >>>>>>>> the >>>>>>>> same modulation rate, same (scaled) power level, claims to be with a >>>>>>>> single dB or two as sensitive as the 4096QAM radio with an 800mhz >>>>>>>> smaller operating range? >>>>>>>> >>>>>>>> Anyone? >>>>>>>> >>>>>>>> Thanks :) >>>>>>>> >>>>>>>> --- >>>>>>>> Josh Reynolds >>>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* >>>>>>> Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 >>>>>>> <https://maps.google.com/?q=3577+Countryside+Road,+Helena,+MT+59602&entry=gmail&source=g> >>>>>>> [email protected] | http://www.packetflux.com >>>>>>> <http://www.linkedin.com/in/fwchristian> >>>>>>> <http://facebook.com/packetflux> <http://twitter.com/@packetflux> >>>>>>> >>>>>>> >>>>>> >>>>>> >>>> >> > >
