He’s bought an 868 MHz Jeelink for a reason, and changed the code to 868 MHz for a reason, and I would expect that reason to be that, like me, he has an 868 MHz system, which is quite possible given its age.
The answer, @Franz, is if you don’t know or aren’t sure of the r.f. frequency you’re working on, compare the RFM modules on all your items with the pictures.
@borpin Yes, I am replacing a defunct Pi with a Jeelink on a Ubuntu VM.
@Robert.Wall I will check pictures, but stuff was ordered for 868Mhz, antennas are short (about 110mm), code on my EmonGLCD uses 868Mhz, code on my EmonTX was left to default (the frequency #define is commented out). My old EmonRX on the Pi had a short antenna and was able to receive signal from EmonTX placed 3 rooms away…I would say that at 99% I have a 868Mhz.
And yes, I have the SMA connector. The signal quality does not change much if I remove the antenna… that’s why I think there is something wrong with it. Tomorrow I will try to solder the antenna on the RFM12B
Worthwhile checking your SMA antenna is compatible with the SMA socket i.e. in the centre there is a clearly a male pin to fit into the opposing female socket. There are many SMA style antenna that have a reverse connector i.e. no centre pin. The resulting air gap will surprisingly pass some signal, but very weakly - hence drastically reducing range.
A quick and easy way to test would be to simply push a piece of wire of the correct length
into the SMA socket on the PC board. If it works, that points to an antenna issue.
If it still doesn’t work, then something on the PCB is bad. (SMA socket, solder joint, etc)
Good call, emjay.
At first I thought “the only RP SMAs I’ve seen/know about are for wi-fi.”
Turns out they’re indeed available for more than just wi-fi.
e.g.https://www.l-com.com/wireless-antenna-900-mhz-3-dbi-rubber-duck-antenna-rp-sma-plug-connector?gclid=EAIaIQobChMI2t3Qtb-c6wIVCXiGCh1DoguVEAQYDSABEgLoRvD_BwE
At first I tried this approach and I removed the antenna and inserted a 8cm wire into the base of the SMA connector (I do not have a reverse connector).
Signal did not improve. I thought that my approach was not the correct one.
Now I must try to solder a wire to the RFM12B board… but I am scared to damage it.
Are you sure your JeeLink clone has an original Hope RFM12B radio module? They are often cloned as well. Here are a couple of originals that illustrate different radio chip packaging (not relevant here) and target frequency band. The sprinkling of SMD components to the left of the radio chip are filter/matching parts whose values all change according to the target ISM band. By chance, one of the required C values for 868/915 MHz operation is so small, it is omitted completely (upper left edge, near the crystal as marked).
Hopefully your unit eventually springs into life - the RFM12B is quite robust but can be damaged by running full power without an antenna load.
There are more pictures in Learn→Electricity Monitoring→Networking→Which radio module→Identifying different Radio Modules
Hello. Thanks for all the information.
I soldered an antenna wire in place of the SMA-connector antenna. Signal improved a lot and now the antenna seems to work fine (antenna can get signal from a device placed “two doors” away).
I still get some “unreliable signal” sometime but I think I can live with that.
Here is the picture of my device.
CONCLUSION:
Thanks to your help I managed to replace a defunct Raspi+Rmf12b with a cloned Jeelink that was initially set for the “FHEM” environment (had to reflash it).
The Jeelink is connected to a 32bit-Ubuntu 18.04 virtual machine(with emonhub and emoncms) that runs on a 10+y old laptop with “Core2duo” processors. With some tweaking it works quite fine!
I AM HAPPY WITH THIS SETUP!
Side note: I had to use a 32bit ubuntu virtual machine because of my host pc restrictions. For some reason the “emonscripts” did not run fine in a 32bit ubuntu (maybe because it is kind of an unsupported environment). Scripts ran fine on a 64 bit ubuntu 18.04. I noticed that the variables on “config.ini” were not passed to the “main.sh” and so I run the “main.sh” commands by hand.
I’m running emoncms on Proxmox on a laptop. I reused some additional memory but that is a really good solution, especially for backing up.
Good to see you got it going, especially considering your trepidation about soldering. 
For what it’s worth, regarding:
www.jeelabs.org/jl3 is still dead to this day
but https://jeelabs.org/jl3 (without the www) points to https://web.archive.org/web/20170220045356/http://jeelabs.net/projects/hardware/wiki/JeeLink
which seems to have limited relevant information such as the board schematics etc.
