POCSAG, FLEX paging

[etherxrally]

Hey guys, I have been following along for a while and was happy to see some sdr action enter into the scene. I live in the north bay and have been watching some of the paging systems that are around here. Typically these are high power stations (some low band VHF, some High band VHF, some 400Mhz but mostly 800mhz) so getting a strong signal is easy with a stock rtl-sdr antenna. I am using PDW in windows (http://www.discriminator.nl/pdw/index-en.html). it may be worth while for members of this forum to check out. The amount of data that pours over the air from these is amazing. They send out data that isn't just local to the area but often is from other parts of the state. I have seen personal medical information get relayed from one medical staff to another during shift changes, status of equipment get sent out to techs (servers, HVAC, communication gear), Basketball game stats, Names of clients to be picked up by taxi services with contact numbers etc. I don't know if pagers are so old school they have been over looked or people just aren't interested in what they see but it seems to me that there is potential here. I would think that people smarter than me could write a program to sort this out by sender and start logging lots of info on a target. Check it out and see what you think. Keep the segments rolling, good stuff!

[etherxrally]

If you are in the bay area you could try looking between 928 and 931 mhz and you should see some action.

[ElfnetCommunications]

Paging systems range in operating frequencies

in the 90's most operated in VHF-Hi band on 157.740 or 152.480 but traffic there is now very very rare.

800MHz systems are more likely to be police, fire, or ems related where 900MHz systems are general usage.

if you have a volunteer fire dept and know the frequency they use for radio comms then chances are they will have pagers on that frequency if they have a paging system. most fire type pagers are 2-tone voice with a Pocsag 1200 or 2400 piggyback. In house hospital and trauma dept pagers will most likely be pocsag 512, 1200, or 2400 or a mix of each including flex 9600.

back in the 90's radio shack marketed a private paging system that operated on 27.145 Mhz i think is what it was.

A good tool to have aside from you sdr is a pretty decent handheld police scanner so you can band search for things and make notes when you dont have your computer setup on hand.

[fuzzy_bunny]

I remember Light and Dark Industries advertising and selling pocsag decoders in hardware. I have the schematics in an old issue of an electronics magazine. Unfortunately, the copyright is not yet expired by date, otherwise I would post it. It is actually a really early example of Software Defined Radios.

And Apple was founded by guys making blue boxes used to defraud the phone company of long distance charges.

But I ramble.

-Fuzzy Bunny

Edited March 15, 2014 by fuzzy_bunny

[jobdone]

I'm interested, is it mainly FLEX or POCSAG that you hear stateside. We get a mix over here in the UK, but it's mainly FLEX.

[etherxrally]

I dont know what is more common. Most of the time i set the decoder to decode both and didn't pay much attention to what mode was detected. I can say that the two pagers I have to have for work are FLEX. I suspect that Elfnetcommunications would know more about which is more popular and maybe will chime in with a little better idea of what we see here. I was playing around with PDW and found that there is a filter built in that I didnt see ealier. Its much like a wireshark for paging.

[Karit]

In NZ there is still plenty of POCSAG

Followed the steps here

http://www.raspberrypi.org/forums/viewtopic.php?f=41&t=45142&p=357671

And got the grewuencies from

http://www.radiowiki.org.nz/index.php?title=Scanning_Data_Modes_in_Auckland

[ElfnetCommunications]

I found a GOLAY paging system on 42.180 MHz yesterday. I though all that was dead.