LimeSDR under SDR-Console

#175

Marty,

Agreed. Proves it’s in the code / firmware, not the applications.

#176

Latest firmware installed. Here are some data points:

OpenHPSDR Hermes board using SAM 12 kHz BW
7.435 NF -105 Signal -50
9.505 NF -120 Signal -45
15.140 NF -120 Signal -45

LimeSDR + SDRConsole
7.435 NF -114 LNA_L -104 LNA_W -104 LNA_H -98
9.505 NF-115 LNA_L-92 LNA_W -91 LNA_H -83!
15.140 NF -114 LNA_L -73 LNA_W -71 LNA_H -56!!

Readings taken off the S Meter in SDRConsole.

LNA_H surprised me at 9505 and 15.140

Much better than it was before the Firmware upgrade.

Mike

#177

I am using gqrx on ubuntu 16.10 instead of sdr-console, but I can also corroborate seeing the following on V1.4 w/ latest firmware.

  • FM mirrors in 20-30Mhz
  • reduced sensitivity below ~122Mhz (compared to rtlsdr)

tried all the different RX ports w/ not much difference.

I determined this using a cheap rtlsdr & antenna, using the same antenna and comparing the output in gqrx.

can post screenshots if needed.

not sure if related, site note* but also seeing a persistent spike on the centerline hardware freq.

#178

Thanks for the info.
I am waiting my v1.4 limesdr. Above 122Mhz is better than rtl-sdr?
Thanks.

#179

Simon, I get those side issues also here…

#181

I’ve had a break through on the LimeSDR sensitivity on 6M through 432.

The key is to turn down the internal Lime LNA and use an external LNA for the band you’re on. Also, pay no attention to the frequency markings on the antenna ports. Try all three and use the best.

I’ve been using a GVA-63 for testing as I had one here all made up for another project (5760 driver). Not a very good NF.

On 6M, I started out at -115 as the reference for MDS using the LNA_L port. I changed to the LNA_W port and went down to -123. I then inserted the GVA-63 which only has 7 dB gain and went to -128. This is with the internal Lime LNA set at -15. Any higher and it’s just noise. I bet a higher gain LNA will lower the MDS further.

I saw -128 to -141 on 2M. On 222, picked up 7 dB and on 432 10 dB. 222 and 432 weren’t too bad to start.

I plan to try some PGA-103’s which have a much better noise figure.

Looking up!!

Mike

#182

Kit: https://www.dropbox.com/s/rksf6uwv3yfxmym/SDR-Radio%20V3%2C%2064-bit%2C%202017-02-07_1555.exe?dl=0

This is a new one - initialises correctly on HF.

Seems to be very deaf on HF, as far as I can tell none of the packages have resulted in acceptable HF performance, am I right?

#183

Simon, correct, HF is down, and no broadcast AM band, Medium Wave to the EU guys :slight_smile: but performance in the real world not on a signal generator, but on antenna is dismal… At least 40db down on even the RTL with upconverter… And this is on real antennas. Not bits of wire, a 4el 6 band beam and a 1500ft loop…just for starters…

Paul - NN4F

#184

I just check AM at 9840. Hermes board -46 dBm. LimeSDR -96 dBm. I did find the LNA_H port was about 8-10 dB better than the other two RX ports.

#185

Guys, be careful how you compare different receivers. Do not compare absolute signal levels (dBm) because (1) it needs calibration and (2) even calibrated, different hardware can have different absolute levels.

I know many SDRs display “dBm” but it’s mostly nonsense unless the device really has been calibrated across the its frequency range. Try to measure the signal to noise ratio instead using similar bandwidth and FFT settings.

#186

@csete Alex, which ever way you view it, the signals are in the mud compared to any sdr, even an rtl/upconverter combo is better on HF… And the difference on the 1.2 to 1.4 boards is clearly down, see @martywittrock’s samples…

#187

Yeah, I had similar experience when I tried some time ago with my v1.2 board.

#188

@nn4f_radio as stated elsewhere, a comparison of a v1.2 to a v1.4 board at this stage is not conclusive, since we have not ruled out possibility of firmware/software changes. Improvements have previously been made after discovering transceiver configuration/programming errors and correcting these.

#189

Hi Andrew,
I’m not sure if I understand you correctly. Are you saying that the v1.4 board needs to be looked at, firmware and/or software wise, to bring performance in the 100 kHz to 30 MHz up to standards? And will this action be taken?
Waiting here for my LimeSDR and I can’t say that I am happy with the news on performance in the 0.1 to 30 MHz frequencies so far.

#190

Alex,

You are 100% right. So I went back to my Hermes and set it for 3 x 384k stitched receivers. 1.1 MHz BW. FFT set at ~ 11 Hz

On my Lime, 2.5 MHz BW was the lowest I could select in SDRConsole. FFT showed 9.5 Hz
On 9.505 MHz, strong religious broadcaster, Hermes showed peaks at 70 dB above the noise. Lime showed 45 dB.

Not 100% scientific… But this is typical of what I’m seeing.

Mike

1 Like
#191

Thanks for the update Mike.

#192

Alex,

Just so we have balance here (and I’m in the HF camp and always have been), what has your experience been as far as performance of the LimeSDR running it on the Weather Satellite frequencies as compared with other SDRs you’ve used? I just want to know if it’s better or worse. Let us know your opinion for 100 MHz and greater (frequency) performance.

73 de Marty, KN0CK

#193

I check schematics , the input circuit is designed for > 700MHz only , so If you need low frequency you must modify input circuit. The spec. of LM70002M is 100KHz-3.8GHz but I don’t know why Lime design team designed input circuit very bad, there is no input filter as RTLSDR or SDRPLAY. There is no way to improve HF by software , you need to mod input circuit for using with HF.

#194

@martywittrock It worked well and I have posted my results while the crowdfunding was running. I have not done any side by side comparisons to other SDRs.

At this point there is so much confusion between hardware/firmware/driver versions, theoretical specs vs. practical experiences that I think I will stay quiet until I have my device in my hands and can do more tests.

2 Likes
#195

There is no hardware mod to improve the low frequency sensitivity.
I did some measurements and found there is a small internal capacitor in series in front of the LNA. It results in a high input impedance with - even more important - a high Q at low frequencies. Such a network can not be matched at a wide bandwidth.

Lime seems to be aware of it. Or why do they specify the input parameters only down to 100 MHz?