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Hi Ian,

The 433 Mhz frequency used by OEM lies in a portion of the radio spectrum allocated to Industrial, Scientific, and Medical devices, as well as an Amateur Radio band.

Given the radio modules used in the OEM system don't have a great deal of selectivity, i.e. the ability to reject unwanted signals, it sounds like what you're seeing might be the result of interference from something operating at, or near 433 Mhz, located in the general vicinity of your equipment.

Regards,

Bill

MartinR modified an emonGLCD as a RF spectrum analyser signal strength meter, if I remember correctly [I didn't!]. It would be worth looking up that post.

MartinR modified an emonGLCD as a RF spectrum analyser, if I remember correctly.

Hi Robert,

Is this post you're referring to? http://openenergymonitor.org/emon/node/2395

Martin called it a RF Signal Strength meter, but it looks like it could be useful for troubleshooting Ian's issue.

and here's another one showing a transmission clash, I think this is OOK from my weather station...

You're right Bill, I ruminated on it a while then it took me more of a while to find it! I'd edited my post before I'd seen yours! But it still wasn't bad for 2 years ago.

I think the only reason I remembered it was I'd made a comment on Martin's post.
Hopefully, it'll help Ian resolve his issue

I have converted a RFM2Pi firmware to use the RFM69CW  RSSI value to plot a scope like trace over a serial port, similar idea to Robin's waveform tools, seen as a vertical realtime trace in the arduino IDE (or minicom etc).

The "trace_mode" can be selected as a function on a fully working sketch, so when you suspect there is something adrift you can just dial in and take peak without changing sketches. It isn't as tidy as Martin's glcd method and he uses a 10bit adc attached to the rf signal rather than reading an existing value of only 100 steps, but it doesn't require a hw mod or glcd and it seems to work ok.

The sample rate is variable from 0.1 secs to 2.5secs in 0.1s steps, quiet_mode, group, promiscuous mode and frequency adjustments work as usual to help filter/tune the issue.

I will tidy it up and post it over the weekend.

Paul

Many thanks.

I have an  emonGLCD so I will build the the signal strength meter ready to monitor if it happens again. I can only think something is operating periodically that is interfering with the signal. This is strange as we have no immediate neighbours. We are one of the few residents surrounded by holiday homes which are seldom if ever occupied. The only things that the owners leave on are the boilers. We have keys so I can take my signal strength meter into their property and see if the signal changes.

Regards

Ian

I performed the emonGLCD mod and have used it for troubleshooting and antenna testing - it's great!  

In my neighborhood there is a TON of 433mhz traffic going on.  We have smart power and water meters... the water meters are the main offender, blasting out 20 second long strings at very high power.  I have my emonTX in the same room as the RFMPi receiver, but the smart meters mounted outdoors on the surrounding homes block any communication during their bursts.  Fortunately they are not too frequent.

I also discovered interference in other places where you wouldn't expect it.  For example, I took the emonGLCD to a farm out in the middle of nowhere.  I was surprised to see there was a lot of traffic as well.  In that case I tracked it down to their Davis weather station which was fully optioned with multiple soil moisture sensors, leaf wetness sensors, and the irrigation system remote which was also interfering.

Antenna testing:

Offending transmitter on farm:

I know you are going to go the glcd route, but just as a follow up to my previous post above, I have now posted the code for Adding a trace_mode to rfm2pi firmware as promised.

Paul