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Nick Foster bistromath at gmail.comHackRF sends 8bit samples, same as the RTL dongle. 20Msps * 8bits * 2 (complex sampling) = 320Mbit/s, or 67% utilization. The Ettus B100 gets 10.6Msps on most USB host controllers, sometimes 12.8Msps if you have a really nice USB host controller with nothing else on the bus -- 71-85% utilization with 16bit samples. You can double that if you select 8 bit sampling mode for the B100, for 21.3-25.6Msps, at the cost of dynamic range. The RTL dongle appears not to be able to continuously sample above 2.4Msps for reasons that are unclear to me, but certainly not due to a USB2.0 limitation. --n On Sat, Sep 21, 2013 at 2:37 PM, Leif Asbrink <leif at sm5bsz.com> wrote: > Hi Adam, > > > > > The bandwidth of the I/Q pair is too large to be transmitted > > > > over USB for the reception of TV signals. After demodulation > > > > the bandwidth is lower so it would (marginally) fit an USB > > > > interface if we talk about traditional analogue TV. For digital > > > > TV the bandwidth reduction by the decoder is much larger. > > > > Is that correct? From what I can find, an analogue TV signal has a > > bandwidth of around 6-8MHz. > Yes. > > > The HackRF is an SDR that works over > > USB2.0 and can capture a chunk of RF spectrum up to 20MHz, which > > should be ample for one analogue (or even digital) TV signal, perhaps > > even two if the channels are close enough together. > > I was under the impression that the USB channel was the reason that > the highest sampling rate I was aware of in continous mode is 4 MHz > (QS1R) Now, I did not think of the fact that for the dongle we need > only 8 bit while normal SDRs use 16 bit so with my assumption the > maximum sampling speed would be 8 MHz. To receive 6-8 MHz bandwidth > one would need to sample quite a bit higher. Surely one could apply > digital filters but even so a, substantial amount of oversampling > is needed. > > Are you sure HackRF really can send 20 MHz of bandwidth over USB 2.0 > continously? Where did you find that info? (Seems I should try to > push SDR manufacturers who use USB 2.0 to supply modes with higher > sampling rates...) > > 73 > > Leif > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/osmocom-sdr/attachments/20130921/02ac3624/attachment.htm>