[aprssig] An amusing aside (Text Pagers)
Don E. Wisdom
donw at engineeringinc.com
Thu Jan 28 12:23:02 CST 2010
Current models are expensive... Bravo 800/802 & Advisor II's are almost $100 apiece! In pager land you get what you pay for... the cheaper Divas/brand of the week disintegrate with normal use :)
I can get 5 gallon buckets full of Advisor Golds on government frequencies for very very cheap.
They'd need the receiver changed out most likely & the xtals changed and it realigned. There were 3 or 4 splits of the VHF receiver boards if I recall correctly.
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf Of Erik Finskas
Sent: Thursday, January 28, 2010 11:16 AM
To: TAPR APRS Mailing List
Subject: Re: [aprssig] An amusing aside (Text Pagers)
Scott Miller wrote:
> Buy enough of them, and you can get them from the factory on whatever
> frequency you want. Though I've never seen one as low as the 2m band.
> And getting the off-the-shelf pager hardware to demodulate AFSK would
> likely be impossible, I suspect.
Most of the current models are frequency agile by design. The older
models rely on a crystal or other fixed frequency source to determine
the frequency. The national paging network in Finland (decomissioned
about five years ago) was just above our 2m band, at 146.325MHz...
Unfortunately 99% of the equipment was old enough to meet the dumpster
rather than undefined amount of work to get them to 144MHz.
We purchased a batch of programmable alphanumeric pagers from a dealer
called Mutual Aid Supplies some years ago to start up similar project,
to do ham paging, but that did not fly due to lack of coordination and
generally, time. The pagers were about $100, available in both VHF and
UHF. A preliminary network design was drawn, with a hot-spot solution in
mind to spread low-power POCSAG transmitters virtually anywhere with
If the transmitters of a paging network are not frequency synchronized,
they need to be timeslotted. (Of course, this only in case that there is
100% coverage with overlapping coverages of transmitters). That would be
a interresting algorithm to design to make sure there are geographically
no transmitters near each other transmitting in a single slot. I recall
we thought of a 10 second slots, and if retransmissions would be needed,
they would take place in the next slot for the current TX.
The modern pagers are capable of detecting duplicate transmissions and
Now I would think UHF is better place to put Ham Paging, as it has
better penetration to buildings and UHF PA gear is generally well
available. Additionally, the transmitters could be co-located with APRS
nodes, and being on UHF, there would not be problems with paging
transmissions blocking the APRS receiver.
But, VHF is good too as we have a pile of 200W transmitters ready to do
One good application for ham paging is also filtered DX-alerts..
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