Problems with adapting the ASK Example to 15 MHz


#1

Dear community,
My colleague and I are trying to adapt the ASK example from https://github.com/myriadrf/LimeSDR_Workshop to 15 MHz for some days now. The goal is to modulate some information on a 15 MHz carrier with, for example, an 800 kHz sub carrier and measure this with an oscilloscope.

The first approach was - after loading the corresponding DEMO_1Msps_866MHz-50dBm.ini file in the LimeSuiteGui - to change the frequency on both, the TX and RX path (SXT & SXR tab). Furthermore, we have tried the solution of @martywittrock from his posting (Where did the 100 KHz go?), but this also did not lead to the desired success.
Of course we have read and tried the whole “limesdr-made-simple-…” tutorial as well as the different hardware descriptions, datasheets and other tutorials (i.e. from Danny Webster), but we currently have no idea how to solve this problem.
Maybe there are some geniuses who could describe the steps necessary from scratch for solving this challenge.
Thank you in advance for your help
best regards
Martin


#2

@Martin_T - Martin,

There are two methods of performing this:

1.) Use GNU Radio Companion and the applicable LimeSSDR plugins. An excellent write up of this is here —>

https://wiki.myriadrf.org/Gr-limesdr_Plugin_for_GNURadio

All one would need to do is set the carrier frequency to 15.0 MHz and then modulate that carrier (not certain if AM or FM) with 800kHz. All this is capable with PC resources and the LimeSDR. Measuring on the scope just requires that you have the sweep speed at a reasonable setting to see the resulting envelope for the 15 MHz being modulated by an 800kHz source.

2.) Use SDRAngel to achieve the same thing - all the information to make that happen is here —>

You would need to set up the proper environment (Windows or Linux - Linux preferred) and then set up a FM or AM modulating source that is driven by the PC at 800 kHz. Setting up the 15 MHz is kind of tricky but if you choose to go that route with SDRAngel I can set you up with the settings necessary to make that work - just ping me here in the forum.

The choice is yours - choose wisely…

73 de Marty, KN0CK


#3

@martywittrock
Hi Marty,
Thanks a lot for this detailed information and for the fast response.
We tried the first method a few days ago, but for some reason we could not generate and measure a modulated signal at such a low frequency. We took the “signal generator” example as template and tried to adapt it. I think we will try again next week, maybe we missed something the last time. Do we need to configure some special settings in the LimeSuiteGui when working with the Gr-limesdr Plugin or is this handled by the various blocks in the plugin?
The SDRangel you mentioned above looks very interesting, confusing but interesting. I think this option sounds very promising and we will try to manage this next week as well. If we have any questions regarding this tool and the mentioned 15 MHz settings i ping you for some assistance.
Thanks again for your help
best regards
Martin


#4

@Martin_T - Martin,

I think one of the issues you have to look at pertaining to your modulating signal in GNU Radio Companion is that the modulating bandwidth maybe limited - you may want to check the parameters of the modulator to ensure it can accept an 800 kHz signal as most modulators are used for voice and slow data (10Hz - 20 kHz) and at 800 kHz there wouldn’t be any modulation present because it’s getting lowpass or bandpass filtering characteristics. I would encourage you to review your flow diagram in GNU Radio Companion again for that issue - you’re going to see the same thing with SDRAngel unless you’re FM’ing it and using a wideband modulator (sink device) and it can accept 800 kHz, too.

Check that criteria and get back with us on the forum - let us know how you progress there.

73 de Marty, KN0CK