POCSAG Pinephone Hardware Add-On; Radio Silence, Privacy, Anonymity,and Freedom

[tllim]

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Check this out: https://hackaday.com/2021/05/18/send-old...-hardware/

and https://www.soldierx.com/bbs/202105/Pock...ransmitter

Seems like using HopeRF RFM23BPW module. HopeRF is the company who teachs Pine64 on the Lora module design and tuning :-)

For the i2C to SPI protocol conversion TinyAVR design, just follow the PinePhone finger print back cover code and here is the link: https://github.com/zschroeder6212/tiny-i2c-spi

Upthread I have several cheap ways to send POCSAG pager signals below regulated power levels, for simplicity I have been using a HackRF/Portapack H1 and it gets the job done with ease and I have one handy so while I have other tx hardware I mention, it sits in boxes for now.

The RX chip looks interesting though especially if there is a partnership already with hopeRF.
Truthfully if we could do radio silent RX on both commercial POCSAG messages AND LoRa for local p2p RF messaging that would be even more useful than a one use receiver.  Of course it would require other local users with LoRa for the off-grid p2p comms.
The question is if we want to invest effort in a software or hardware decoding for the POCSAG as I think that will be the more important daily driver use of the module even if we do also have LoRa.
I have over the years realized that switching a phone into a POCSAG RF silent mode should massively increase battery life so I hope that this module can be in a low power mode like an old 90s pager and still be able to reliably receive a commercial or amateur radio paging signal and usefully decode it.
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I am not sure if I see an amplified signal out pin on the RFM23BP but that was a quick look at the datasheet, we would need to have that signal form a tuned frequency if we wanted to use a hardware decoder chip, at least for the POCSAG both for power savings and I think it is more reliable to use a hardware decoder into something with memory to cache messages until the Pinephone does a wake cycle and clears that cache into incoming messages.
If we are going to be doing LoRa I think you should spec the highest quality frequency control crystal that HopeRF can provide or eeven consider resoldering a self-provided crystal as you can do some wildly low powered tight signals if you can be certian that both the rx and tx are on the same tightly tuned frequency.  We might even consider WSPR mode where we could over several hours be able to transmit or receive very short messages over hundreds of km using nothing but bounces from terrain, overflying aircraft, and meteor ionization trails; though the really best way to use WSPR is to have a good external tuner and then use the WSJT decoder program on the repos over an audio line. https://www.physics.princeton.edu/pulsar/k1jt/wspr.html
Just for reference you can use even the moon as a communications satellite using WSPR protocol, a good yaggi antenna, about 100w of power(anyone who can solder can build that amp), a very stable oscillator(that crystal we were talking about and/or a GPS signal discipline injector) transmitter, and even a pinephone to decode the returning signals assuming you also have a very stable frequency receiver with another very tight yaggi or big dish antenna.

The PinePhone LoRa back cover samples already ready, jump PM me and I will ship one to you. Antenna design using flax PCB and still ahve room to improve.

One the crystal question, for sure needs to use low ppm type and also every production batch needs to fine tuning for optimum performance. HopeRF has provided spectrum analyzer and teach us how to tune.

On the P2P LoRa mesh, please check out Meshtastic.