I’m looking at getting a LimeSDR however I’m a digital nomad, and so size, weight, and ruggedness really matter. Does anyone have any measurements of the dimensions and weight of the Acrylic vs Aluminium cases available on CrowdSupply? Any experience of how well the cases survive being thrown around etc?
Also, one of the things I’m looking at is use for receiving (and maybe sending) spread-spectrum (FHSS) in the 2.4GHz ISM band. Firstly, how quickly can the LimeSDR change (TX/RF) frequencies, ideally without custom firmware?
Secondly, I’ve read some discussion that the 60MHz bandwidth limit may be able to be circumvented with custom firmware - that the limit is the USB3 bandwidth rather than on-board. Has anyone worked on this? For example, I’d like to monitor 2.4-2.5GHz, and while it would be great to send the full datastream to the PC, it would be sufficient to, for example, just send a custom datastream reporting frequency spikes above a certain noise floor - which could then be used to ascertain the frequency hopping algorithm/key used by a 3rd party.
In terms of ruggedness, I would watch out if you plan to heatsink the LMS7002 device on the board. There have been documented posts here where a LimeSDR user found that his heatsinked LMS7002 BGA came off the board when his case fell onto the floor from an undetermined (but certainly off a table or similar) height. The device sheared itself off the board because of the mass of the heatsink and the immediate strike of the fall from the case transferring all that energy onto the board and the LMS7002 came off. It’s possible that this may have been an aberration (not likely to happen to all LimeSDRs) but I’m just cautioning you that ANY SDR should be treated with a certain amount of care when transporting it. There’s no documentation on the LimeSDR (or any other SDR for that matter) that is can survive shock and transport vibration that I know of.
Again, being the Digital Nomad that you are, if you’re planning to buy the LimeSDR or any other SDR be advised that they’re not all ruggedized (unless you buy a MIL-Spec model). Most have BGAs and if there’s enough shock because of an impact the potential for damage or the part being displaced off the board is very real. I know of no SDRs with BGAs that do underfilling to prevent this from happening.
Thanks. Yeah, I’m not expecting mil-spec - I have a load of normal electronics as well - but I know some hobbyist types of kit can be very easy to break. Thanks for the heads-up about putting a heatsink/fan on - that’s a perfect example.
You must also take care on USB connector side. When in Luftek case, connector
is exposed and drop on that side can not be happy end…
Because of that BGA story I have only one heatsink covering LMS7 and FPGA
and all secured with zip tie over the whole board.
@ 9a4db
hmmm you have one heatsind over both?? you have a “step” filed in your heatsink?? …
i just added a heatsink to fpga (yet) but plan to also glue one on the transceiver chip (if i made some component changes first)
my plan is to build a multiband transceiver with it (when upmixer biard comes available up to 10 gig)
… @kingtut
why not homebrew a good case?? al cases are cheap … some sma pigtail cables and youre set
No, have just flat piece of heat sink, but 3 layers of silicone heat pads under
on transceiver side and just one under FPGA. The step shoud be approx 0,7 mm in
case you like to make one. My Lime in Luftek case is happy now with 31 to 33 C temp
readout / active cooling ON.
My decision is to go with some Anaren DBM instead of up-mixer board from Lime…
helps to clear spectrum output too
@dg9bfc
Possibly. The main problem is I’ll only be ‘home’ (with parents, in the UK) for about 4 days around Christmas. After that I’ll be heading to Egypt, South Sudan, or Iraq - none of which are great for electronic supplies or Amazon deliveries But I’ll definitely look into possibilities - it’s great that detailed schematics of the board are available.
All
To get 100MHz (or 160MHz max) coverage, I’m wondering if I can set the frequency to be mid-band, ADC @160MHz, then NCO to up/down shift before decimation by 2. However I think this will exceed the bandwidth of USB3. Is it possible to convert the 12-bit sample size to 8-bit - e.g. by dropping LSBs - for the transmission between the FX3 and the PC?
When using Rx only, the bandwidth of USB3 allows something like 2 x 60MHz (using 12 bit samples). I think it would be possible to drop LSBs in FPGA but you would have to modify FPGA and LImeSuite code to do that.
if USB3 is the limiting factor, you can easily use LIMESDR-PCIe.
I also wish to monitor 100 MHz but saw that this is not possible for one RX channel.
If you use 2 RX channels then there is the problem of ADC Synchronization.
Unfortunately I’ll be using a laptop, so can’t use PCIe.
Interesting point about ADC sync - I would have thought they’d be operating off the same on-board clock so that wouldn’t be a problem. Still, I don’t think it’ll be a problem if I don’t try to combine the two RX channels.
KingTut…
If I understand your needs correctly I will suggest the following options based on my experience traveling with a lot of electronics equipment (couple of years since last visit to Egypt…)
Since it appears that your main goal is to be able to travel with your equipment (right?)
1.- LimeSDR aluminum case. My recommended (the one I use)
Looks like a comercial electronic device, removing the antenas and storing everything in a portable hardrive case make it look not threatening …
Very compact…
2.- LimeSDR acrylic case
Larger foot print, still looks like a comercial product but will most likely get whoever is checking your luggage attention. Nice transparent and lime green colors.
3.- I will discourage a home brew case since it will really attract attention to the device… you will be ask a lot of questions of what it is? What is for? Etc…
Thanks. Good point about packaging. Unfortunately I’ve ordered a homebrew case, however it is very small, so I wonder what I can do it make it look less dodgy…
The last time I looked, which was probably a year ago, the advantage of PCIe was lower latency.
The reliance on an external xillybus FPGA code to provide the PCIe interface layer limits throughput to ~200 MB/s each direction which is comparable with USB 3.0 at 400 MB/s in total.
But there is the possibility that at a later date, more throughput will be available with updated FPGA gateware. The limit on the throughput is not a hardware limitation. I should probably clarify that I’m talking about bytes/second over the data interface and not MHz of spectrum bandwidth through the ADC part of the LMS7002M.
Xiillybus FPGA code limits throughput to 400 MB/s per direction (Cyclone IV PCIe x4, Download Xillybus for PCIe | xillybus.com). When using TX and RX the maximum what I am able to get in LimeSuite on LimeSDR-PCIE is ~370 MB/s in each direction. On LimeSDR-USB it is ~180-190 MB/s in each direction.
@IgnasJ how do you reach such limits with the PCIe board? Could you detail your settings? With both PothosSDR and GQRX, I get max 55MSps. For now, I’m just trying to display the FFT, nothing more.
I still haven’t found how to do it in LimeSuite (documentation on LimeSuite is scarce…). With pothos and gnuradio, I managed to reach 289MB/s on the former and a little less on the latter (10MB less or so I think).
Could you send a simple limesuite ini file, for instance centered around 2.45GHz ?
At 340-350MB/s, do you know if that’s possible to do FFT with a cpu or shall I go to Cuda, and on which parameters of the FFTmay I play to alleviate work?
The maximum sample rate that can be set is 80 MHz, however the practical limit I think is something around 60-65MHz as with higher rates bit errors start to appear. So using single channel you cannot get 300MB/s data rate
INI file centered at 2.45 GHz (LNAH) and sample rate 61.44 MHz.
To get 300+MB/s data transfer rate you need to select MIMO (uses 2 channels) in FFTviewer.
But I’ll definitely look into possibilities - it’s great that detailed schematics of the board are available.