R820T vs. E4000
al at eartoearoak.com
Sun Mar 17 18:17:38 UTC 2013
I've just pushed some updated code up to GitHub, you can now set the
gain in the preferences and tweak the scan settings. There's some info
A 250kHz offset seems to work well with my E4000, 140k with a FC0012 and
100k with a R820T. The FC0012 is the noisiest and the R820T is quietest.
Hope it helps,
On 17/03/2013 11:00, Benedikt Heinz <zn000h at gmail.com> wrote:
>> For me the most interesting plots were the "no antenna" ones, showing the LO
>> leakage ;-) If I understood clearly your plots, you have at some places high
>> power ghosts. Maybe you are close to powerful transmitters, but this is more
>> probably a LO to RF isolation problem: the receiver receives himself...
> I did two new measurements with the gain set to 20 in RTLSDR-Scanner.
> The files with the -gain20 in the filename  show the new results.
> There are more spikes from the R820T LOs now, but it's still less than
> with the E4000 I'd say.
> The good thing is that the DVB-T stations as well as some other
> signals can be found as expected now.
> 2013/3/16 Al <al at eartoearoak.com>:
>> I think you've run into a couple of issues, firstly it appears that the AGC
>> isn't fully disabled on the R820T (if you remove the aerial the noise floor
> It looks like gain=0 just was too little for the R820T. gain=20 seems
> to be a good start.
> Maybe exposing the gain-value in the regular UI would make sense?
>> Secondly RTLSDR-Scanner averages 2 chunks of bandwidth either side of the DC
>> point, these seem relatively quiet with an E4000 and FC0012 but I haven't
>> had chance to check the R820T yet. This tuner may have a very different
>> noise floor. I was wondering about adding a feature to allow the user to
>> pick their own segments (by terminating the aerial and looking at the noise
> Ah, that's interesting. I was indeed wondering how you avoid the DC
> spike and my pathon skills are close to zero ;-)
> According to , the R820T doesn't use a Zero-IF, so there should be
> no DC-spike at all.
>> Has anyone had a chance to test 2 different dongles with the same tuner?
>> I'd be interested to know if it makes a difference to the noise floor, if
>> there is little change, I could vary the scan based on the tuner.
> I do have two E4000 and two R820T dongles, but I haven't yet compared
> the noise floor.
> I'm thinking about a per-dongle baseline file w/o an antenna for
> compensation. This approach should be more robust. Otherwise you need
> to shift the baseline spectrum according to the frequency error.
> Best regards,
>  https://docs.google.com/folder/d/0ByDAKwyEiyx_XzZ5ZnpRV1VZWDQ/edit?usp=sharing
>  http://lists.osmocom.org/pipermail/osmocom-sdr/2012-September/000253.html
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