I have a LimeSDR USB-A rev 1.4s that seems to be functioning hardware wise however I am unable to get it to receive any signals. All I see is the noise floor and not much else. Gain settings have relatively little impact to the signal and only raise the noise floor slightly In terms of modifications I performed the easy fix on RX1 - L and RX1 - W when I first got the device. I see a signal in FFT viewer while performing a loop back test, but unable to receive much, if any, signals in other software. I have a second LimeSDR USB B Micro that seems to be working great.
Just to make sure it wasn’t firmware related I downgraded the gateware to 2.14 with similar results.Any ideas on how I can test further? Any help is appreciated.
Thanks,
Any ideas or causes for the lack of reception? Is it possible that something in the receive circuit burnt out or was damaged somehow? I’ve hardly used this unit and don’t suspect that I did anything to damage it.
@jslatten - Justin,
I wouldn’t jump to the conclusion that there’s anything defective in the hardware yet. A few weeks ago I was totally convinced that some of my LimeSDRs (V1.4 unit mind you) were defective…I would try them on SDRConsole and GQRX and they would work marginally on HF…and even that way on SDRAngel, too. I was gutshot because the HF performance fell off, and the V/UHF performance seemed correct. Then I added a post on the forum about SDRConsole not operating in HF and within time Simon found that things had changed in the firmware for the LimeSDR to the effect that it didn’t function well on his V1.4 Limes, too. Once he fixed it and I tried it on my V1.4 Limes with the correct firmware, everything fell into place again. Even the latest compiled SDRAngel worked great.
The moral to this story is: All LimeSDR firmware is not created equal. Within the past month there’s been significant changes to it that caused some of the applications to become very broken, and as a result we’re all walking around wounded with ruddy Limes…And so, you have to determine what apps work with what firmware and then you’ll be good to go. For me, that’s the most plausible cause of '…suddenly it doesn’t work anymore…" syndrome. We’re trained by life and cause/effect to blame the hardware when things don’t work, when in reality you might have firmware loaded in the Lime that just doesn’t play well with the apps and seems kind of dead. So go back to basics…Get your firmware loaded to the versions that the apps play with right and then see what your Lime performance looks like. If you’re using a Windows Platform, SDRConsole seems to play right with the latest-latest firmware. If you’re using SDRAngel, the latest version seems to play right with the latest firmware, but transmit is all screwed up (for now). GQRX seems to play right with the latest Lime firmware, too (as does CubicSDR).
Hope this helps - don’t give up.
73 de Marty, KN0CK
@martywittrock I’m not really sure where to go from here. It seems like something is wrong with the receive amplifier, but not 100% sure at this point. I just noticed that the LimeSDR that’s working is a rev 1.4 versus the newer one that is not working which is Rev 1.4s
I’ve attached a 30db amplifier in front of the unit which allowed to pick up some signals so it definitely seems something is wrong with the onboard amp or perhaps matching network…
Not long after I got my LimeSDR-USB, I must have knocked one of the input transformers which pulled off either a primary or secondary wire off the solder pad. It made one of the receive channels as deaf as a post! I had to put it under the microscope to find this out - it is so small. It might be worth checking your board for a similar problem.
@jslatten - Justin,
If you own a illuminated magnifying glass, DO check out the area around the ports that you think may be intermittent or dead as @picofarad has suggested and look for clear disconnections from the matching networks (transformers, wires that have come loose from the pads, etc). Frankly, there have been issues in the past that the other SMD inductors and capacitors have popped off the board because of brittle soldering in the reflow ovens or a bad stencil job. The MN18 and MN23 inductors that are removed to provide HF coverage could be removed with a dental pick - normally, that’s not possible with other assemblies. I actually had to desolder my chip inductors off the Lime to make it play on HF, but a friend of mine used a dental pick and it came right off without damaging the pads. So you REALLY need to look at coupling caps and inductors in the same path to see if they came off the board and rendered the port open.
Look for those issues and then check back with us - pics will be great if you find anything, but that’s the most plausible reason why your Lime is deaf because it takes a lightning strike or strong ESD direct hit to kill it at the chip level. Again, hope this helps -
73 de Marty, KN0CK
@martywittrock and @picofarad
Thanks for those suggestions. I used some fine tweezers to pull the inductor off.I performed the same procedure on my LimeSDR rev 1.4 board and it has been working great. I also wondered if something wasn’t right from the surgery but I can’t see any particular damage to the transformer or the pads. I’ve attached a few pictures to see if you or anyone else can discern anything.
@jslatten - Justin,
Not seeing anything out of the ordinary from my thorough look on the board…I’m stumped on this one. But do take a very close look at the port that’s dead or weak and see if there is anything you can see on the matching network at all - that’s the most likely culprit because all the other components look good to me.
73 de Marty, KN0CK
Thanks @martywittrock . I’m at a loss too. I scoured the board for about 45 minutes trying to find something but I’ve come up empty handed so far. Both the RX1 L and RX1 W exhibit the same signal issues so unless both ports are somehow damaged it seems it may be somewhere else that are common between the ports. I wonder if there is any way to test whether the amplification portion of the circuit is working properly?
AA7QQ
5 April 2018 03:27
10
Have you tried the RX2 side?
Ed
I’m trying to find a program where I can use the RX2 side. SDRAngel seems to lock up when trying RX2
@jslatten - Justin,
As much as I hate to say it…The only thing in common with those two ports is the LM7002… …Let’s hope it’s not that…
73 de Marty, KN0CK
Here’s some more information. Using SDRAngel on the LimeSDR 1.4s with the signal issue I’m seeing these weird error messages:
Reference clock 30.72 MHzhttp://wiki.myriadrf.org/Lime_Suite#Flashing_images
Reference clock 30.72 MHzhttp://127.0.0.1:8091
Any ideas as to what could be causing the MCU errors?
@andrewback @Zack
from the log DeviceLimeSDRParams::open: cannot init device LimeSDR-USB seems to be comming from SDRAngel, so if it does not configure board to working state, then it’s not surprise that calibrations fails.
I just noticed I’m also getting these same MCU errors in LimeSuite…I’ve set all of the defaults and both RX/TX calibration is failing.
[09:32:20] INFO: Reference clock 30.72 MHz
Note: I just recently downgraded the gateware to 2.12, but I am getting exactly the same errors with 2.15, 2.14, etc…
save your board config to .ini file and post it here
[file_info]
Config looks good for A channel, A channel is working and calibrating normally. B channel is not configured, so if you are trying to use B channel it won’t work and won’t calibrate.
I don’t think I’ve tried to use the B channel. A channel fails on calibration when I click the calibrate button. I get this error message:
[10:24:53] DEBUG: MCU algorithm time: 0 ms
which LimeSuite version you are using? Help->About
