After digesting this information, a couple of questions came to mind. 1. Pertaining to the crystal tolerance, a figure of 20 ppm was used in providing guidance to choose certain settings. However, at the bottom of page 31 there is a statement saying that the range is more like 50 to 100 ppm. Is this a reference to something different?
The second Q I have regards the aging of these radios. I have a pair of 915 MHz RFM69HCs that I have been using for some time (3 mo) that work predictably. Recently I purchased some replacement parts from a NA Hope distributor as backups. The problem is that while the newer parts will communicate with each other, they do not communicate with the older radios. In my testing, I use the same hardware and software, initializing the radios identically. At first I thought that perhaps I was dealing with a manufacturing variation but after reading about the possible changes that can occur over time I am wondering if it might be aging related. Do you think that it is possible for two radios to communicate with some devices but not others when all conditions and settings are equal, and if so, is the solution a matter of individually tuning one radio or the other?