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LimeSDR

limemicro.com

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Re: LimeSDR

#41

Post by sliken »

WrtCdEvrydy wrote: post #26
atonse wrote: post #9

SDR is one of those technologies I still want to play with that I feel will open up this incredible new world to my curious mind. All of a sudden, the invisible waves around us that we often tangentially know about but never think about (because we can't see, smell, or hear them), become a whole sixth sense to explore. I really hope for some free time to play with this, and to expose this invisible world to those aro…

The best one is the ADS-B Out from airplanes, you can map the planes around you with a $20 widget.

Similarly you can map out lightning strikes with similar tools/methods.

Re: LimeSDR

#42

Post by sosborn »

CSSer wrote: post #38
WrtCdEvrydy wrote: post #26

Earlier quoted context omitted.

The best one is the ADS-B Out from airplanes, you can map the planes around you with a $20 widget.

This sounds really cool. When you say 'around you', what kind of radius are we talking?

It really depends on the environment around you. I live deep in valley, so my range is pretty limited to line of sight.

Re: LimeSDR

#44

Post by moftz »

Blackthorn wrote: post #2

Does anyone know of a solution that can go down to the 5khz range? Older (...and even newer) gym equipment uses the gymlink protocol for heart rate monitors instead of low power Bluetooth and friends, and very few monitors support it anymore. I wanted to try to make a converter but couldn't find anything to output in that frequency.

5KHz is pretty low, it would be difficult finding anything in the ham category because no ham bands are that low. You would need to probably build your own receiver. The good news is that 5KHz is super low frequency and could easily be received with a crystal detector. Antenna connects to an LC resonator centered at 5.3KHz, pass the result of this through a diode and then into a microcontroller. Many have analog input pins and analog comparators built-in that can trigger an interrupt. You would need to figure out what voltage level you expect to see from the detector when a heart beat signal is sent and then apply that voltage to the other side of the comparator. Some microcontrollers even have a real analog voltage output that could allow you to adjust the voltage through software. The microcontroller would then trigger an interrupt and do something every time a heart beat signal is received (send it through serial to a PC, compute heart rate, display something on a LED screen, etc).

If you need to broadcast at 5.3KHz, that's pretty easy too. There are numerous designs out there for a basic CW transmitter (https://makerf.com/posts/ten-minute-transmitter). You may have trouble finding a crystal centered at your 5.3KHz frequency.

Re: LimeSDR

#45

Post by themodelplumber »

marcodiego wrote: post #39

LTE, GSM... Does it means it is now easier to build an entirely free device that can be used as a cellphone?

You mean with proper licensing? That might be the tricky part; use of the rf spectrum is probably monitored and regulated, depending on where you're at in the world.

Re: LimeSDR

#46

Post by themodelplumber »

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.

Same here with the monitor, I have an old Dell 24" from 2006 that I somehow keep around. I've learned not to expect much if my ham radio is within 3 feet of it. Probably fixable with some clip-on parts but for now it's easier to scoot the chair over...

Re: LimeSDR

#47

Post by tzs »

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.

My Samsung monitor does that.

It's bad enough that I lose several channels on my Samsung TV when my Samsung monitor is on if the TV antenna is in the same room as the monitor.

Re: LimeSDR

#48

Post by structural »

tzs wrote: post #17

The couple of times I've had something I wanted to do that needed an SDR more powerful than than an RTL-SDR and decided I wanted a LimeSDR or LimeSDR mini...the lead time on them has been such that it would not arrive in time for the project I wanted it for. Right now, both LimeSDR and LimeSDR mini orders place now don't ship until Feb 28 2022, except for the LimeSDR PCIe which ships Sep 29 2021. (You might be able t…

Components for producing SDRs are impacted by the overall semiconductor shortage very significantly, too: keeping stock of what are fairly niche products is difficult when times are good, but with component lead times in the 52-80week ranges (and still increasing), there's absolutely no room to adapt to what customers might want a year from now. It really sucks for everyone.

Re: LimeSDR

#49

Post by iNate2000 »

octopoc wrote: post #7

One of my concerns with using an SDR is that the FCC basically requires DRM[1]: > ...importers and marketers should ensure that [two-way radios] are properly certified and labeled as FCC-compliant and cannot be easily modified to operate outside its grant of certification. So if you use an SDR for LoRa, you have to make it hard for users to modify the code to emit a different frequency. [1]: https://docs.fcc.gov/publ…

That document (DA 18-980) talks about "importing two-way VHF/UHF radios... used primarily for short-distance, two-way voice communications."

In other words: cheap walkie-talkies that don't comply with FCC regulations.

Such radios typically max out at 5w.

The LimeSDR claims 10dBm - which I believe means about 10milliwatts.

In other words, that FCC memo is concerned with radios being sold that are something like five hundred times as powerful as a LimeSDR. And therefore much more likely to interfere with other transmissions.

Re: LimeSDR

#50

Post by stagger87 »

syedkarim wrote: post #36
stagger87 wrote: post #23

Earlier quoted context omitted.

> However in order to legally use the tx-capabilities of an SDR you probably have to be a ham anyway. You can transmit in the ISM bands without a license. There are still power restrictions which most SDRs won't exceed anyways.

Yes, a general user/consumer can transmit in the ISM band without a license, but they are still required to use intentional transmitters which have been certified by the FCC.

> but they are still required to use intentional transmitters which have been certified by the FCC.

For a hobbyist experimenting with an SDR, this wouldn't apply.

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