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LimeSDR

limemicro.com

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Re: LimeSDR

#111

Post by rfdave »

drmpeg wrote: post #70
jacquesm wrote: post #21

Earlier quoted context omitted.

Before you start pumping out that kind of power I'd invest in a spectrum analyzer (which are surprisingly affordable today) to ensure that the signal that goes out is clean. Those mini SDRs when used for transmission will output a ton of harmonics because they are almost by definition not going to have any filtering on their output because that would limit their usability. When used for reception that is not a proble…

That's for sure. Here's what an Ettus B210 (now $1472, not cheap) looks like with a fundamental at 145 MHz. 3rd harmonic is only 10 dB down. Power was 0 dBm (with a 20 dB pad on the analyzer input). https://www.w6rz.net/harmonic.png

It's inherently a broadband device, with no output filtering. No surprise that the output is full of harmonics. I built several application specific RF front ends for Ettus SDR's at a previous job, it's mandatory for any kind of professional use.

Re: LimeSDR

#112

Post by fortran77 »

ohazi wrote: post #71

I wish them luck, but judging by the ~week I spent trying to get a LimeSDR mini to work, their product is so half baked that it's basically not fit for purpose, and if you're considering getting one, I'd recommend something with an Analog Devices front-end instead. The PLL would fail to lock at random frequencies and temperatures. You'd try to scroll through e.g. the 2.4 GHz ISM band and would randomly get downconver…

I had the exact same experience. It’s junk. Get a USRP if you can, or perhsps a bladerf if you’re a hobbiest.

Re: LimeSDR

#113

Post by [deleted] »

syedkarim wrote: post #107
touisteur wrote: post #102

Earlier quoted context omitted.

Ah thanks. Yeah I was more going on the side of 'build your own phased array' and (I think) needed coherent receivers for that. 299usd is an amazing price for 5 channel rx. And, since the schematics and everything (?) is open, it might be a 1-semester EE end of studies project to extend it to 32 or more :-) Thanks for taking time to answer my questions. This project looks amazing, can't wait HW availability.

Although the direction-finding and passive radar software are both open source, the hardware is not (so no schematics, layout, BOM). Just wanted to clarify that for you and anyone else reading this thread.

[deleted]

Re: LimeSDR

#114

Post by madengr »

opwieurposiu wrote: post #32

SDR made me understand how much RF noise my desktop computer emits. Lots of spikes between 400-500mhz. Could be my monitor also, as scrolling text seems to emit the most noise.

Yeah, now PC come in damned glass cases. So much for the FCC.

Re: LimeSDR

#115

Post by TaylorAlexander »

toomuchtodo wrote: post #76
TaylorAlexander wrote: post #72

Earlier quoted context omitted.

It’s very fun! I use it to monitor for low flying aircraft around a farm where I am doing some drone experiments. The legal drone limit in my area is 400 feet above ground level and near the hills some aircraft fly pretty low, so I’m going to ground the drone any time an aircraft is nearby that is not above 10kft.

I highly recommend not relying on SDR ADS-B reception alone and also checking online data systems for ADS-B that also use multilateration to track aircraft using their transponder when they aren’t ADS-B capable. Otherwise you might be operating under the assumption there are no contacts in your working airspace when there is aircraft present but not announcing their location. https://flightaware.com/adsb/mlat/

Sounds like a good idea. Thanks for the suggestion.

Re: LimeSDR

#116

Post by sonic414 »

ohazi wrote: post #71

I wish them luck, but judging by the ~week I spent trying to get a LimeSDR mini to work, their product is so half baked that it's basically not fit for purpose, and if you're considering getting one, I'd recommend something with an Analog Devices front-end instead. The PLL would fail to lock at random frequencies and temperatures. You'd try to scroll through e.g. the 2.4 GHz ISM band and would randomly get downconver…

Tried to make it work for a big project. Spent a lot of time debugging. I was suspecting the code at first. But finally realized the Radio wasn't working correctly. Couldn't return it or get a replacement.

Re: LimeSDR

#117

Post by georgeplusplus »

ohazi wrote: post #71

I wish them luck, but judging by the ~week I spent trying to get a LimeSDR mini to work, their product is so half baked that it's basically not fit for purpose, and if you're considering getting one, I'd recommend something with an Analog Devices front-end instead. The PLL would fail to lock at random frequencies and temperatures. You'd try to scroll through e.g. the 2.4 GHz ISM band and would randomly get downconver…

This has been my experience. I traded mine out for a HackRf

Re: LimeSDR

#118

Post by userbinator »

stefan_ wrote: post #29
octopoc wrote: post #16

Earlier quoted context omitted.

I mean if you used an SDR in your consumer product. Let's say you make a dual purpose LoRa / WiFi radio to put in vehicles for a fleet management solution. If you use an SDR, you'd have to lock it down with DRM to prevent end users from repurposing it.

Yes, but the same applies to your WiFi router even if it has hardware filters. Its simply a certification requirement. That doesn't have anything to do with LimeSDR. This is already not a product that is certified for anything. It exists in a very gray zone where anyone using it for transmission is likely in violation of the law unless they obtained a development/testing license in the specific band they are using.

In a Faraday cage, no one can hear you transmit...

Re: LimeSDR

#119

Post by mycall »

ohazi wrote: post #92
azinman2 wrote: post #90

Earlier quoted context omitted.

Which USRP do you use? And what do you do specifically with it?

A B205. Mostly playing around with high spectral efficiency digital modulation techniques like PSK/QAM and OFDM using GNU Radio. Trying to shovel as much data as I can between two links with as little power as possible. I'd like to experiment with below-the-noise-floor communication, but haven't gotten there yet. It's sort of silly, because you can do all of this in simulation, but it's more fun with real hardware. E…

You could take a look at Intel's Falcon 8 drones [0]. It might get you thinking differently, and the things they pull off a the Olympics is amazing.

[0] https://www.intel.com/content/www/us/en/technology-innovatio...

Re: LimeSDR

#120

Post by ngz00 »

themulticaster wrote: post #95
ngz00 wrote: post #88

Any suggestions on where to start to use this as a LTE uplink that reads from an SD card and uploads images? I'd like to replace my expensive faulty game camera subscription.

In addition to what myself248 said: In case you aren't familiar with the details of consumer RF standards (including IEEE 802.11, but especially LTE or anything cellular related) or don't have some prior RF knowledge: To put it mildly, LTE is not an easy standard to implement on an SDR, especially if it's your contact with SDRs. Even GSM is nowhere near a simple stack. If you want to get a feeling for what kind of ce…

I appreciate the insight, thank you!
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