This is an early mockup of a NB-IoT/4G/3G/2G/GSM Hat just to illustrate the space needs. My main concerns are signal quality on the antenna part as this module do not have a direct antenna output. Below is a PCB snap-shot showing the details of the antenna layout.
I really could have needed a 3rd layer here to completely isolate the antenna signal, but this has to do. The LoRa unit have antenna on the module so I can use a pre-made Antenna port air-with wire, but I will need to do something similar with the GPS.
SIM7020E also have a bigger brother with GPS in the module, so I will consider that as well. I have not sorted passive components and PSU yet – but, a 4G module is usually no wimp on sending, so I expect that much of the spare space I seem to have here will be used on special voltage PSU – not sure yet.
SIM808 that I used earlier is larger, cover only 3G, but it had GSM and PCM sound. The later is digital sound enabling voice services like IVR etc. The drawback with SIM808 was size and the need for 4V/3A as well as the 3G limitation.
The advantage of actual sound support is that we can make a remote doorbell unit directly connected with voice and video to your phone. I will however re-investigate that option using a different path because 300Kbps is actually sufficient for both a voice and video channel. Video will work with reduced frames per sec, but that is sufficient to see what is happening.