Sunday, 20 April 2014

Monitoring POCSAG Pager Messages on 138.150

1705452  14:29:43 19-04-14 POCSAG-4  ALPHA   1200   LAMRT One of the spare radios is missing from mob 1. Please check your bags and return it as soon as possible. Steve 14:29hrs 19-04-14
0271905  14:37:49 19-04-14 POCSAG-4  ALPHA   1200   EMCS WOULD LIKE TO CANCEL A CALL OUT


1981006  15:26:02 19-04-14 POCSAG-4  ALPHA   1200   LLMRT Ref. R057744 12 YR OLD LAD HAS NOT BEEN SEEN FOR 2 HRS HAS WATER AND ON THE  LLANBERIS PATH 07714957260 15:25hrs 19-04-14 L @

1981006  15:38:15 19-04-14 POCSAG-4  ALPHA   1200   LLMRT R057744 Continue to stand by no contact with informant John Grisdale 15:37hrs 19-04-14

0940412  15:45:30 19-04-14 POCSAG-4  ALPHA   1200   KSMRT   tl taking call. Kath 15:45hrs 19-04-14

0944132  15:57:20 19-04-14 POCSAG-4  ALPHA   1200   KSMRT   FT Call out . Ankle injury poss Yarlside. Respond to base or Cross Keys RV with Kendal Team. Adrian 15:57hrs 19-04-14

1999084  16:44:52 19-04-14 POCSAG-4  ALPHA   1200   16.39 BMRT snatch incident @ Windgather Rocks. Vehicles required. Respond to  01298918918. Ta Janette

1999084  16:44:49 19-04-14 POCSAG-4  ALPHA   1200   BMRT standby inc windgather. All mobs en route. Thanks Rob S

 0951348  17:53:11 19-04-14 POCSAG-4  ALPHA   1200   KSMRT STAND DOWN CASUALTY ALL SORTED AND WITH NWAS 17:52hrs 19-04-14

0303562  17:59:41 19-04-14 POCSAG-4  ALPHA   1200   PLS CONTACT BRIXHAM COASTGUARD 01803 882 704

0945873  18:01:29 19-04-14 POCSAG-4  ALPHA   1200   St John Ambulance Cumbria On-Call Team, Daily Test Message.

LAMRT Langdale/Ambleside Mountain Rescue Team
LLMRT Llanberis Mountain Rescue Team
KSMRT Kirkby Stephen Mountain Rescue Team
BMRT Buxton Mountain Rescue Team
EMCS East Midland Central Station (Alarm Monitoring Station in |Nottingham)

All monitored on 138.150MHz

I have just completed the easy discriminator modification on my Uniden Bearcat 9000XLT. I say easy,  the soldering to the PCB at point TP3 had me nervous as it was out of my comfort zone, having been used only to more basic soldering and I was worried about damaging the radio. But I wanted the discriminator tap so much that I figured even if I had to buy a new radio I was prepared to take the risk of possibly damaging this one. I turned off my mobile phone and house phone so as not to be disturbed, but even with shakey hands and a wide tipped soldering iron it was OK and I would do it again no problem. Like all things, it is mostly a case of confidence and being prepared to accept responisibility for any possible damage you may do!

Two tips: get a narrow-tipped soldering iron. If I did it again, I wouldn't use a wide-tipped one. And obvious really I suppose, tin the wire well before you attempt to solder it to the TP3 point.

Phew! With that out the way the world of VHF data decoding is at my fingertips and I have had hours of fun so far. Firstly with AIS using MultiPSK:

Then I experimented with POCSAG pager decoding, using the freely available PDW decoder software, the selected results being at the top of this entry.

I am only just uncovering the wide variety of pager users, and the mountain rescue teams really catch my interest.

I have also built a small line level adjuster, comprising a variable resisitor mounted inside a box with two 3.5mm jack plugs for the input from the scanner's discriminator socket and the output to the laptop, as I wanted to bring the RX level down to a more manageable level, but it functions OK without it if you can't be bothered with any more soldering.

So far I have only sat on 153.15 and the much more interesting 138.15mhz, so there are many more frequencies to try.

73 for now, M6RDP