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Nov 30 07 5:23 PM

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To the new beginner, a radio scanner is a device that allows the listener to eavesdrop on conversations they would not normal hear. In the past, the Police transmissions in particular captivated the attention of many, but most have now gone over to the O2 Airwaves with the other emergency services soon to follow suit. Whats left you may say..

Quite a lot actually..

Here's just 'ONE' idea worth looking into..

A short introduction to Decoding Pager messages.

One aspect of scanning that is not mentioned much and which, Radio Hams have known about for many years is the decoding of those annoying Pager bands that are often locked out by scanner enthusiasts as junk noise!!!. That junk noise is a trappable source of information just like any other voice transmission on your scanner.

With the right PC software, most scanners can decode these Pager Bands!. Thats right, its possible to decode unsecure Pager transmissions with the humble scanner. Read on..

Some background info...

Pager data is transmitted via radio frequency signals in binary format. The way this is accomplished is through the use of tone encoding. Tone encoding is a simple technique whereby a binary zero is assigned say 1200 Hertz tone while a binary one is assigned a 2400 Hertz tone. When a message is transmitted it is sent as a series of tones that switch from one to the other either 512, 1200, or 2400 times per second. Both 1200 Hz and 2400 Hz are audio frequencies. This is a similar technique to that implemented in the tape players used to store data on old computer systems. This technique works well for the wireless transmission of binary data.

One of the most common Pager formats used today is: POCSAG (Post Office Code Standards Advisory Group). Three transmission rates are used to transmit POCSAG, namely 512, 1200 and 2400 bps. Most commercial paging uses at least 1200, although many companies who own their own paging terminals for in-house use transmit at 512 bps.

Pager Messages are broadcast in batches. Each of which is comprised of 8 frames, each frame consists of two codewords separated by a synchronization codeword. A message can stretch through several batches and have as many codewords as needed. So how can a scanner decode these digital transmissions?

You will need the following items.

A scanner with a ear phone socket.
A patch lead (3.5 Male Jack to Jack Audio Cable) I picked up a ready made 5m patch lead for 6pence off eBay the other day.
A PC ( At least a 100 Mhz Pentium is recommended)
POC32 ( A Shareware program found using Google)


Once you have all these items setting up is easy.

Download and install POC32. The shareware version wont allow you to save any data and pops us a message box every 15 minutes reminding you to register the software.

Connect one end of your Audio patch lead to your scanner's Ear Phone socket and the other to your Sound Card's LINE-IN Socket. Most sound cards have a LINE-IN socket as standard.

Program your scanner with some national Pager Frequencies if not already done.

Here are some you can try out.

137.9750 Nationwide Page One (Ex Mercury) Ch2
153.2500 Vodazap
153.3375 Nationwide Paging
138.0750 Vodazap
153.3500 Nationwide Page One (Ex Mercury) Ch3
138.1500 Vodazap
153.3625 Nationwide Paging
138.1750 Nationwide Page One (Ex Mercury) Ch1
153.3750 Nationwide Paging
153.0750 Nationwide Paging
153.4500 Nationwide Paging
153.1250 Nationwide BT Pagers
153.8250 Northern Ireland Air Page
153.1500 Nationwide BT Pagers
454.0750 Nationwide Aircall Voice
153.1750 Nationwide BT Pagers
454.2000 Nationwide Medical Pagers
153.2250 Nationwide BT Pagers
454.2375 Northern Ireland Hospitals
153.2375 Nationwide Paging
454.6750 Nationwide Millicomm Paging
153.2500 Vodazap
454.7750 Nationwide Aircall Paging
153.2750 Nationwide Aircall Comms
454.8250 Nationwide PageBoy Paging
153.3250 Nationwide Aircall Comms
466.0750 Nationwide Hutchison Paging

You can either let your scanner cycle through these frequencies or just select one at a time. Set the scanner's volume about halfway at this point.

Fire up POC32 and if your connections are correct, chances are you will start seeing some grable on your screen after each data burst. The important settings of POC32 is by default, set to Auto, so it will detect the format of the Pager signals and Baud rate automatically.

However, you need to set the volume sound going into your sound card so its as clear as possible. What this means is that you need to now change the Volume settings for your LINE-IN. If you have the Volume Icon shown at the bottom right side of your screen then double-click on this to bring up your sound settings.

N.B If you cant see this icon click on your START button then click once on the CONTROL PANEL Icon. From the list shown, select: "Sounds,Speech and Audio Devices". Then click on the Icon showing "Sounds and Audio". This will bring up a control panel for your installed sound card. The first 'tab' shown (Volume) will have a small box called Place volume icon in task-bar. My preference is to put a tick inside this box. Once done click on the APPLY button with is now ungrayed. Now you should see a small Speaker icon in your taskbar. Smile

Double click on the Speaker Icon. And make sure under Options that the Line-in/Mic is enabled. You will now need to lower and increase the LINE-IN volume until the data from POC32 becomes legible.

A sample output from POC 32 will look like this..

27/01/2007 09:57 CH1 1200 0428917 2 (Alpha) 09:56-21 Inc No. 1352580 - Time 09:55 - at BEST WAY CASH AND CARRY, BRINDLEY RD GRANGETOWN, CARDIFF - MALE- FALLEN - SHAKING - AMPDS 31D01

27/01/2007 09:57 CH1 1200 0042657 2 (Alpha) 09:56-20 Incident No. 1730343 29D02 at CORNER OF SANDPIT LANE AND CLARENCE, CLARENCE RD , ST ALBANS Contact 01234 408969

27/01/2007 09:57 CH1 1200 0931086 2 (Alpha) 09:56-94 EMG No. 3860313: AMPDS - 17, AT: 12 THROGMORTON HOUSE, NEW WALK, TOTNES, TQ9 5GZ Time of Call: 27/01/2007 09:55:05 Tel: 01392 360409

27/01/2007 09:57 CH1 1200 0931086 2 (Alpha) 09:57-95 EMG No. 3860313: AMPDS - 17, AT: 12 THROGMORTON HOUSE, NEW WALK, TOTNES, TQ9 5GZ Time of Call: 27/01/2007 09:55:05 Tel: 01392 360409

27/01/2007 09:57 CH1 1200 1542539 0 (Beep )

27/01/2007 09:57 CH1 1200 1917233 2 (Alpha) 09:57-84 Inc No.

1352580 - Time 09:55 - at BEST WAY CASH AND CARRY, BRINDLEY RD GRANGETOWN, CARDIFF - MALE- FALLEN - SHAKING - AMPDS 31D01

27/01/2007 09:57 CH1 1200 0082641 2 (Alpha) 09:57-98 Inc No.

1352580 - Time 09:55 - at BEST WAY CASH AND CARRY, BRINDLEY RD GRANGETOWN, CARDIFF - MALE- FALLEN - SHAKING - AMPDS 31D01

27/01/2007 09:57 CH1 1200 0290236 2 (Alpha) 09:57-71 Vehicle SN55 OFO has left Dundee DC to deliver to Dundee Metro - ISOTRAK -

27/01/2007 09:58 CH1 1200 0124253 2 (Alpha) 09:57-29 Vehicle DK54 CXL has left Middlewich DC to deliver to York via Northway - ISOTRAK -

27/01/2007 09:58 CH1 1200 0931526 2 (Alpha) 09:57-90 Vehicle DK54 CXL has left Middlewich DC to deliver to York Tadcaster Road via Northway and York - ISOTRAK -

27/01/2007 09:58 CH1 1200 0698786 2 (Alpha) 09:57-35 PLS CALL SUSSEX BEACON.

27/01/2007 09:58 CH1 1200 0151030 2 (Alpha) 09:58-86 14NEW 82640 27/01 0954 NORBITON (FELTHAM MTCE) 3 N *RF* Rough ride reported on Up line by 2O17 at the end of the 20 MPH TSR. Within the 20 MPH TSR. Now cautioning.

27/01/2007 09:58 CH1 1200 1036826 2 (Alpha) NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 09:58 CH1 1200 0042259 2 (Alpha) 09:58-29 NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 09:58 CH1 1200 1090323 2 (Alpha) 09:58-98 NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 09:58 CH1 1200 1200040 2 (Alpha) 09:58-08 WICC @ 10:00. Service Summary: Services generally running within 5 Mins of Time. Infrastructure: No reported problems. Dave/WICC 10.00

27/01/2007 09:59 CH1 1200 1200040 2 (Alpha) 09:58-08 WICC @ 10:00. Service Summary: Services generally running within 5 Mins of Time. Infrastructure: No reported problems. Dave/WICC 10.00

27/01/2007 09:59 CH1 1200 0342003 0 (Alpha) 09:58-17 WICC @ 10:00. Service Summary: Services generally running within 5 Mins of Time. Infrastructure: No reported problems. Dave/WICC 10.00

27/01/2007 09:59 CH1 1200 0698375 2 (Alpha) 09:58-13 3 NEW 222132 27/01 0955 FERRIBY 3 N Melton Lane : 0721 : Up Fast/Main : TRACK CCT -ASTER SF15 / U TYPE SOWC CONTINUOUS, NO TRAIN SOWC OF OWN ACCORD CAUTIONING

27/01/2007 09:59 CH1 1200 0696203 2 (Alpha) 09:59-52 Incident No. 1730345 31D03 at 3, WALVERNS CL , WATFORD Contact 01234 408969

27/01/2007 09:59 CH1 1200 0105871 2 (Alpha) 09:59-02 PLS CALL 01745 344 202

27/01/2007 10:00 CH1 1200 0042612 2 (Alpha) 447623871515

27/01/2007 10:00 CH1 1200 1811560 2 (Alpha) 09:59-48 Delivery from Hinckley DC to Leicester 3 is imminent on vehicle BX05 VOD - ISOTRAK -

27/01/2007 10:00 CH1 1200 0696203 2 (Alpha) 10:00-53 Incident No. 1730346 17B03 at 5 FOUNTAIN COURT, BROOK RD , BOREHAMWOOD Contact 01234 408969

27/01/2007 10:00 CH1 1200 0471368 2 (Alpha) 10:00-30 NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 10:00 CH1 1200 1013668 2 (Alpha) 10:00-31 NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 10:00 CH1 1200 1916183 2 (Alpha) NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 10:00 CH1 1200 0300103 1 (Alpha) NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 10:00 CH1 1200 0300103 2 (Alpha) NEW : LNW (N) GMC Bangor; Ovine Incursion : Driver of 1W80 reports sheep on line near 236mps, services cautioned

27/01/2007 10:00 CH1 1200 1818039 3 (Num ) 101

27/01/2007 10:00 CH1 1200 0679002 2 (Alpha) 10:00-95 1525 : TA,Mark Walters-07796195378.,Extended,, 07-01-27 09:57:48,

27/01/2007 10:00 CH1 1200 0041771 2 (Alpha) 10:00-17 EMMA - CLIENT MR MCLAUGLIN - HOLLYOKE, RARNET ROAD, Aberdeen,AB11 8SA,, CLIENT ON 01224877752 - WATERDAMAGE CLAIM - ASKED YOU TO CALL COSTOMER - THANKS

27/01/2007 10:00 CH1 1200 0931360 2 (Alpha) 10:00-26 Delivery from Livingston DC to Cumbernauld Extra is imminent on vehicle SN56 CHX - ISOTRAK -

27/01/2007 10:01 CH1 1200 1811591 2 (Alpha) 10:00-56 Incident No. 1730346 17B03 at 5 FOUNTAIN COURT, BROOK RD , BOREHAMWOOD Contact 01234 408969[size=12]


You need to bear in mind that the clearer the signal you receive on your scanner, the better it is to decode it. Interference will degrade and corrupt the incoming tones. So if this happens choose another frequency.

Radio Hams on this forum will know that the audio amplifier circuits of all scanners modify the sound output so as to place emphasis on the speech in order to make it more understandable, the amplifier also eliminates any sub-audible tones that may be present in the signal which is not good when decoding Pager broadcasts. If the scanner has a line-out jack then this is of course a better option to use than the Ear jack. Modifications to the scanner can be made to tap the audio before it reaches the discriminator but wanted to show in a simple way, how almost anyone with a scanner can decode Pager Broadcasts without too much complexity.


Happy Scanning!
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