Thank you everyone for the speedy replies! I'm going to reply in order here:
As a simple troubleshooting suggestion: what happens if 1. you don't solder the module to the big giant pad and 2. you don't solder your antenna to the big giant pad either but instead 3. solder your antenna directly to the RFM69 module itself? That's what I've been doing lately on most of my experimental nodes, and it works great.
I tried that last week, I scratched out the trace leading to the large pad and the soldered the antenna directly to the module and I didn't see any considerable change. I have also tried scratching out the pad entirely to eliminate the capacitive effect it may be having and that hasn't seemed to make a difference. You can see a picture of that change below. What I must say though is that I haven't done a range test with the new scratched out pad, rather I have checked the peak output power on our spectrum analyser. I will range test tomorrow. May I ask what RF settings you are getting the success on? I am worried this may be a factor of the huge deviation.
Ah, I think I see the problem on the RFM69xW. It appears you don't have any traces leading to either of the GND connections on the module. I'm surprised it works at all.
[Edit: looks like the same non-grounding connection with your RFMHCW module as well.]
On the bright side, this should be easy for you to fix.
Sounds like you're doing interesting stuff. Can you at least let us know what your system does? It's always nice to hear a bit more from new posters rather than--more often than not--they post some narrow technical question and then disappear forever after it's answered without so much as a peep.
I'll answer all of the grounding questions here, yes all of the ground connections are made via a ground plane. Which explains the "unconnected vias". I didn't include the planes in the screenshot since it would make the layout a bit tricky to see.
In terms of the project, I am developing an updated version to a mesh networked fire detector for use in informal settlements. Our company is called Lumkani, you can find us here:
http://www.lumkani.com. The informal settlement setting is a nightmare for RF, I just came back from a day of RF testing with the RFM solution as it stands and we are seeing around 7m of patchy range. Which just isn't good enough and is far worse than the MRF49XA that we used before. Based on community reports we were expecting well over 100m in community and +300m open field. We are trying very hard to diagnose the issue because as it is, we are in a very tough place, in terms of our current time line. Hence I am seeking help from some RF wizards!
I bet you're right. That would explain the narrow traces and all the seemingly unconnected via holes....
But why does he have via holes on his antenna pad? I guess the pad is on both sides? Why do that?
In terms on the antenna pad, I too question why it is like that! It is a legacy feature from our old device which was included a while back due to some manufacturing considerations with regard to conformal coating. I wasn't with Lumkani at the time but I am very open to changing that, provided the antenna pad remains on the back for the same manufacturing considerations. And to clarify, yes the pad is currently on both sides. However on the scratched off version I mentioned before I removed the bottom pad entirely and kept a small chunk of the top pad.
Would it be better to make a longer trace to the antenna pad that could be smaller and single sided and then perhaps ground stitch the ground plane around it?
I have also attached a picture of our antenna, it is a 50 Ohm antenna, is that what the balun expects? What sort of impedance conversion is it doing? Should the LNA impedance be left at 200?
How likely is this to be a code issue? I can't think of a setting that would affect range so drastically...