Haha, yeah, I am still confused, but luckily, two things are certain:
a) My current setup is stable, after buying these things in order: set of new antennae, higher-wattage power supply, rework.network board+enclosure. I did have to give up on 5G entirely, as the signal is so poor in my area that it was still falling out of 5G into 4G about once a minute.
b) The RM502N-GLAA itself is functional (for much of this time I was not able to rule out the possibility that the modem was bad and that the MCUZone board+enclosure was fine. This was ultimately the reason why I took a chance and bought the rework.network box even though its top rating is 10W max.
Letâs add a bit more confusion, shall we? After reading various hardware design guides for other 4G and 5G modems and their power characteristics, I am leaning towards the possibility that the failures were due to insufficient voltage, not insufficient current. My reasoning is this: none of the guides say that the modem will shut down itself with insufficient current, but all of them say the modem will shut down itself with insufficient voltage. I suspect that the instability I was experiencing was sharp, quick shutdowns followed by rapid reboots.
Thereâs no way to prove this without attaching a precise logging voltmeter capable of reading down to the thousandth of a volt at fractions of a second (with no or minimal averaging). Either that, or if the modem itself keeps logs internally, read the logs to see if it shut down due to insufficient voltage.
Then again, I did have to give up on 5G use with the rework.network 10W board. Perhaps 10W is just not enough to achieve a stable connection with the extremely poor 5G signal in my area. Put another way, perhaps the rework.network 10W box is in fact providing at most 10W, and I am indeed exceeding its power capabilities, but the failure is a graceful drop out of 5G into 4G, unlike with the MCUZone box that had very disgraceful drops out of 5G.
I wonder: would a board capable of supplying the full rated 18.5W give me stable 5G? I even went so far as to buy a SECOND rework.network box that claims to supply up to 20W to the modem. With this, I could transfer the RM520N-GLAA into it and find out whether 10W is not enough to attain stable 5G. I have the second rework.network box in hand but donât have the correct power supply for it (it is 5V, 4A). Finding a high-quality, trustworthy 5V, 4A power supply is surprisingly difficult. The ones I am looking at are typically used to power Single Board Computers like the ODROID XU4.
So, Iâm not quite done with my experimentation.
I am also considering buying a 4G CAT12 modem for $30 or less and putting it into the MCUZone unit to see if it works. If it does, then I will have proven my hypothesis to my satisfaction: Based on the number of capacitors in the power circuit on the MCUZone board, I suspect they used a reference design for 4G modems and didnât update the design for 5G modems.