Below 30Mhz on LimeSDR Mini - Full of garbage

Just change freq to HF. Set sample rate to 1536, LPF to 40MHz and you can receive down to 5.5MHz. For entire HF increase sample rate and LPF (but you need to change RF input of Mini). Also, use GFIR as band filter (set to 0.4 for 20m for example).

Not seeing any difference between what I got with SDR Angle and SDR#. Seems to not hear anything no matter the gain setting. (On ANT_W)

Maybe my AM and FM filters are making the signal to weak for the LimeSDR? Even when its perfectly fine on my RTLSDR.

I just don’t know what else to try. I have had this thing for well over a year and haven’t gotten it to work for the reasons I bought it. Which was to use it as an HF ham radio for down to at least 20m.

Do you see any change in noise level when gain is changed? NCO is automatic for freq. below 30MHz but if board is not cooled properly or it is faulty local oscillator can’t lock 30MHz (as reported here on forum from HAM radio member from Czech republic). Do you see difference in band noise between 40-35-30-25MHz? What is board temperature?

The noise does change but it is all very low at -90 dbm according to SDR# Even with the gain maxed out.

Board temperature is 46.0 - 48.0 C which is what its seems to stay at even when I just plug it in for the first time in the day.

Since device is not under warranty you can open metal cover and check input circuit. Schematic is at:


Check page 5, RX1_W input is identical as LimeSDR-USB (700-900MHz) and EasyFix1 and 2 for HF is applicable. High resolution image could help to compare with working device. If you don’t have necessary skills tray with local cell phone repair guys (usually they have microscope, BGA welding tools…).

Here some tips, who knows, may be useful to someone…

Have here one LimeNET micro which was not used on primary intention.
Assuming that RF part is similar to mini consider this approach:

I was able to use on 7 MHz with Ron’s SDR Console all gain to max and LNA4ALL
but that is only Win solution and no use of on board CM3.

Therefore decided to try with Raspibian and Soapy Remote…
Managed to install all that and find out that Cubic SDR is working on remote
and SDRAngel crashing - the author reply was:
"
Soapy suppport is a workaround for devices that are not natively supported in case this may be useful. I will not make any effort concening Soapy.
"


you can notice presence of SDRPlay RSP1, that was consideration to cover
HF, work nice over CM3 USB with Soapy Remote.

So for the time can forget TX on this setup…

Later with running Cubic SDR find out that on HF even with all gains up, reception is poor or almost impossible bellow 10 MHz.
So here temporary solution till I find out something better:
ICOM PCR1000, IF out on 10.7 MHz
Again sensitivity of Lime was not enough to properly receive 10.7 IF
Let’s try solution with moRFeus in mixer mode, LO on 85 MHz - 10.7 MHz = 74.3 “zero” on IF
Good surprise - moRFeus is able to mix signal bellow 30 MHz (specification)
And this solution is working now fully remote from 100 kHz up to 1.3 GHz
I am setting PCR1000 on start of band, for example 7.000 the rest is on Lime.
Lime is properly passive cooled and temp. stay in 35 C range.

Here some CW contest on 7 MHz running now and I am able to use Ubuntu and Win10 host notebooks for RX all over the local WiFi network, bandwith up to 500 kHz

Messy setup in attic :blush:
Left PCR1000, Mid moRFeus, Right LimeNET micro /with upper case cover removed…

Done for test, 10.7 MHz IF out on PCR1000, C 10nF SMD

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I’ve successfully used SoapyRemote with the server running on a LimeNET Micro and SDRangel running on an Ubuntu 18.04 laptop as client. When using packages on the LimeNET Micro, SoapySDRServer would crash as soon as the client connected. However, this was resolved by building it, SoapySDR and Lime Suite on the Pi all from source.

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Good tip, thank you, must try that again…

My client was also SDRAngel build from source on 18.04 Ubuntu,
crash is on client side on selection, either SDRPlay RSP 1 or LimeNET micro/
please see picture above. Tested Lime USB was running ok on client in direct mode.
After crash Soapy Server still running and can run CubicSDR on any client.
I used SDRPlay RPI SD image and just build from source what was missing =>
Lime Suite and Soapy for Lime.

As an update. After posting that last post I decided to try strapping a big heatsink I had onto my limesdr mini with some thermal pad I have to touch the FPGA. Makes a world of difference on HF. My guess is the thermal noise somehow was screwing up something. (Granted it never hit over 47 C which is what it normally is.)

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Still haven’t managed to transmit because I have been using SDR# for HF because I can’t figure out the NCO when using SDR Angle.

@chibill - William,

The latest version of SDRConsole supports HF transmit and receive for the LimeSDR USB and the Lime Mini from 80m to 6m, and obviously all the other V/U/SHF bands as well. Do a search on Google for SDRConsole and download the latest version for Windows 32-bit or 64-bit. For Linux, SDRAngle can be used for HF transmit and receive on the LimeSDR USB and Lime Mini, too. If you’re doing your own development, SDRAngel is open-source so you can see how the techniques are being applied to the LimeSDR for transmit and receive. Another set of source in Linux that is also accomplishing TX/RX for the LimeSDR USB is LinHPSDR or PiHPSDR. Either version has transmit and receive capabilities for the Lime, too - I think somewhat limited on transmit, but definitely working decently in receive or dual receive modes.

Hope this helps - 73 de Marty, KN0CK

I have tried with SDRConsole but it seems to do something strange and change the audio freq. (Like for FT8 it spreads the tones out.) Most likely because it has to run at such a low sampling rate for SDRConsole to enable TX at all. It receives it just fine though.

I can’t wrap my head around the NCO in the LimeSDR to use SDRAngle. To use to dealing with normal mixers and up/down converters. Which was seen at the beginning of this thread the NCO is apparently not.

@chibill - WIlliam,

When you use the NCO feature of SDRAngel you have to have it enabled and then you set the frequency to 30 MHz. That will perform the subtraction necessary to make SDRAngel work in the HF band. Edouard worked the logic to perform all the frequency management so you didn’t have to think backwards about what needed to be done to make the frequency setting work correctly. There are settings I used that I can send you a screenshot of that will explain all this. The interface is really different, but that’s because Edouard likes LeCroy test instruments and this is how they look. LeCroy oscilloscopes have a VERY similar look and feel to how Edouard put this GUI together. So it will take some time to get used to (it did for me) but when I finally realized how to use it, it was a great application to get the Lime on HF.

I will find some pictures of the settings I use for HF using SDRAngel and post those here a little later on today - please do stay tuned…

73 de Marty, KN0CK

If I want the NCO to be 30Mhz I will have to run at a very high sample rate. Much higher then when I am receiving HF in SDR# or SDRConsole. (Max NCO is tied to same rate from what I can tell.)

@chibill - William,

It’s normal/typical to have a sample rate above 4,000,000 when using SDRAngel - in fact it’s likely that it can go as high as 6,000,000. See attached pics for transmit and receive and settings I’ve used in the past.

RX:

TX:

Let me know if you need anything else, William -

73 de Marty, KN0CK

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Thanks so much Marty for sharing your knowledge. This helped me understand getting the NCO working.

The Soapy driver seems to take care of HF tuning details in GQRX automatically. A little voice on 40 and 80 but mostly rtty. Some AM harmonics. I’m so fortunate to live 7 miles from WBBM AM Chicago! Conditions are poor and it was 1 am on a work night.

I saw that red and white POS AM Tower on my way home today. I’m going to burn it like these loonies burning 5g (and 4g) towers!!! Only joking!

I have an AM and FM bandstop filter just for that reason. :slight_smile: (I like in bridgeport)

Wonder why SDRAgnel needs the sample rate to be so high for use with the NCO when SDRConsole and SDR# doesn’t need it every high at all for listening to 7 meters.

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Thanks. I’m not sure how to verify or turn on the one’s built in to the Lime!

I have very powerful AM and FM stations within just a few miles in the Chicago metro.

I don’t think there are any one spcifically for AM or FM stations inside the Lime itself. I use NooElec ones like that one you have on my 40m half wave dipole.

Also I am in Chicago. Neighborhood is Bridgeport. I am about a mile from US Celluar (Where the white sox play).