The real problem with this thing

Adam Nielsen a.nielsen at shikadi.net
Mon Aug 13 23:58:41 UTC 2012


> This clumsy Analog to Digital Converter / USB
> interface Chip, does not have the Audio dynamic range needed for my
> purposes.

That's because it's only designed for FM radio.  Anything more would have been 
overkill for the manufacturer's purposes.  This is still excellent value for 
$20 and hasn't been much of a stumbling block for what most people have been 
doing so far.

> The infuriating predilection it has to crash every time you want
> to shift frequency is another disadvantage.

I'm not sure where you're looking in the docs, but if you're using Balint's 
USRP ExtIO (as oppposed to the - I think - Osmocom ExtIO) then there are two 
sets of code for the tuner.  The default one offers slightly wider frequency 
range, but crashes as you have seen.  If you add "tuner=e4k" to the device 
hint then it will switch to the newer code, which doesn't crash, at the 
expense of having some gaps in the frequency coverage.

> First, I attached a high gain audio amplifier's input directly to the
> Tuner's output then to a 96K Sample per Second, 24 Bit Audio card to observe
> a high quality spectral image from the tuner.

Presumably this reduces your bandwidth from 3.2MHz to 96kHz, which is 24kHz 
too low to properly receive wideband/consumer FM radio.  Since many people are 
using the RTLSDR has a kind of glorified RF scanner, I am wondering whether 
you're trying to do something you really should be doing on a high end device 
like the USRP?

> Next is to hack into and record the I2C sent to the Tuner, so it may be
> controlled independent of that infuriating RTL2832. If anyone has done this,
> please share your code and understanding.

Don't quote me on this but AFAIK the RTL just passes the I2C commands through 
unchanged.  This is how the existing E4000 tuner code was able to be adapted 
to the RTL2832 so quickly.

This list probably isn't the best place to ask about this sort of thing - it's 
mostly developers focused on improving the hardware rather than getting people 
started with it.  I strongly recommend switching to the ultra-cheap-sdr 
list[1] instead, which has many more people able to help beginners.  Your 
question about the device crashing is answered quite often, for example. 
These people can also point you to the many 'getting started' guides, which do 
explain clearly with screenshots where to put device hints and the like.

Cheers,
Adam.

[1] https://groups.google.com/d/forum/ultra-cheap-sdr (you can subscribe via 
e-mail here if you don't want to use the web interface)




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