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Lime Mini FM test

Posted: 12 Apr 2018 03:29
by pe1etr
Lime mini SDR
https://www.rtl-sdr.com/limesdr-mini-cr ... 5-ghz-sdr/

I found this on youtube FM test 20 MHz bandwidth
video made in Finland (local station ) SDR Console V3
https://www.youtube.com/watch?v=qqoxvx2mTmU

Peter Wilson
BKK

Re: Lime Mini FM test

Posted: 12 Apr 2018 07:14
by zach_m
Considering the RF bandwidth LimeSDR seems to be the best on the market for the price. I am wondering how it will behave in the areas with strong local transmitters? Will 12-bit DDC handle it? I would like to see the test on this one.

Re: Lime Mini FM test

Posted: 12 Apr 2018 11:07
by daveB
Thanks for finding and posting the video Peter.

A couple of things I glean from the video - apart from the obvious that it is running on SDR-console v3. 1) It's playing back a recorded file and it looks like the max individual file length you can get on SDR-console v3 is about 25 seconds (look at the suffix on the file name it changes from 002, to 003 and then 004). The playback is seamless, but if you want to run the files through File Player in SDR# there will be an awful lot of files to go through during an opening. 2) It looks like the strongest signal is about 55 dB above the noise floor and the entire spectrum look very clean.

With a 12 bit ADC it equates with the Airspy One/mini and the SDRPlay RSP1 so should prove adequate for strong signals - at my location the strongest signal is about 60 dB above the noise floor.

You will need a USB 3.0 port to run it. I don't know if you would get away with USB 2.0 with a lower bandwidth - but that defeats the object.

You are almost certain to need external bandpass filtering to stop strong DAB / mobile phones / HF / MW from breaking through - but for a single application this shouldn't be too expensive.

ADD: Just spotted that the LimeSDR mini only works down to 10 MHz - which isn't a problem to FM-DXers.

Re: Lime Mini FM test

Posted: 12 Apr 2018 11:50
by pe1etr
daveB wrote:
12 Apr 2018 11:07
Thanks for finding and posting the video Peter.

A couple of things I glean from the video - apart from the obvious that it is running on SDR-console v3. 1) It's playing back a recorded file and it looks like the max individual file length you can get on SDR-console v3 is about 25 seconds (look at the suffix on the file name it changes from 002, to 003 and then 004). The playback is seamless, but if you want to run the files through File Player in SDR# there will be an awful lot of files to go through during an opening. 2) It looks like the strongest signal is about 55 dB above the noise floor and the entire spectrum look very clean.

With a 12 bit ADC it equates with the Airspy One/mini and the SDRPlay RSP1 so should prove adequate for strong signals - at my location the strongest signal is about 60 dB above the noise floor.

You will need a USB 3.0 port to run it. I don't know if you would get away with USB 2.0 with a lower bandwidth - but that defeats the object.

You are almost certain to need external bandpass filtering to stop strong DAB / mobile phones / HF / MW from breaking through - but for a single application this shouldn't be too expensive.

ADD: Just spotted that the LimeSDR mini only works down to 10 MHz - which isn't a problem to FM-DXers.
You're welcome Dave.
I did mention it was runnng in SDR Console v3 in the original post :)
In fact that's what caught my eye that it was running smoothly and cleanly at 20MHz bw in familiar Windows software.
I suspect the default file size in V3 is 2GB?

I also found a video from Lithuania showing the original LimeSDR running in SDR Console v3, but the aerial was just a length of wire used indoors near the PC and there is a lot of noise, but here it is FWIW.

https://www.youtube.com/watch?v=ZIIJhkQR7Uk

Peter BKK
PS I don't have my laptop with me just a basic tablet so I can't run tests with IQ file size in SDR console v3

Edit The 'Airspys' don't have any filtering either, and they run a lot better with external filters

Re: Lime Mini FM test

Posted: 13 Apr 2018 18:56
by daveB
Hi Peter,

Regarding filters in the Airspys - they state that they have "tracking RF filters" - which I take to mean a tuneable bandpass filter which tracks the centre frequency. In comparison the SDRPlay RSP (not the RSP1A) has basic wideband filters, e.g. 60-120 MHz, that don't have a lot of attenuation - only -6dB in the DAB Band. In contrast the 60-120 MHz filter in the RSP1A has a very sharp cut off and achieves a maximum attenuation of more than 70dB slap bang on the main UK DAB frequencies.

So on the RSP I have DAB signals that register 40-45dB above the noise floor. When I tune to the OIRT band they appear at around 20 dB and tune in reverse. Fortunately by a judicious choice of the centre frequency I can lose them.

On the Airspy Mini - there is not a sign of the DAB signals breaking through. I've attributed that to the tracking filters but I may be wrong. So, of course, the Airspy is the choice when I'm DXing the OIRT band.

Re: Lime Mini FM test

Posted: 13 Apr 2018 19:46
by Patrick73
Has anyone ran an A/B test RSP1A vs HF+ on FM ? The latter is very sensitive (compared to the ELAD S2 at least), but the 660 kHz maximum BW is sometimes a limiting factor (as well as for MW DX'ing)

Re: Lime Mini FM test

Posted: 14 Apr 2018 01:47
by pe1etr
daveB wrote:
13 Apr 2018 18:56
Hi Peter,

Regarding filters in the Airspys - they state that they have "tracking RF filters" - which I take to mean a tuneable bandpass filter which tracks the centre frequency. In comparison the SDRPlay RSP (not the RSP1A) has basic wideband filters, e.g. 60-120 MHz, that don't have a lot of attenuation - only -6dB in the DAB Band. In contrast the 60-120 MHz filter in the RSP1A has a very sharp cut off and achieves a maximum attenuation of more than 70dB slap bang on the main UK DAB frequencies.

So on the RSP I have DAB signals that register 40-45dB above the noise floor. When I tune to the OIRT band they appear at around 20 dB and tune in reverse. Fortunately by a judicious choice of the centre frequency I can lose them.

On the Airspy Mini - there is not a sign of the DAB signals breaking through. I've attributed that to the tracking filters but I may be wrong. So, of course, the Airspy is the choice when I'm DXing the OIRT band.
There is a lot of advertising hype about Airspys not needing filtering. Check out Lief's webpage and his youtube channel, if you can sit through his one hour videos.

http://sm5bsz.com/

www.youtube.com/user/sm5bsz

Peter
Bangkok