Fun with HAM radio

Using a scanner to listen to radio can be both fun and exciting. In Sweden it is legal as long as the information is not spread.

Choose the right scanner

Technical postorder companies like Hobbex and Teknik Magasinet offers a wide variety of scanners. The scanner of your choice should have as wide frequency range as possible. A good scanner can scan all frequencies between 0.5-1300 (at least) MHz with NO GAPS. A normal scanner have gaps but can scan the usual frequencies. Here are the frequencies of a typical standard scanner that costs about 2000 swedish crowns.

66-88	MHz
118-174	MHz
406-512	MHz
806-956	MHz

Listening to local transmitters

Some interesting frequencies (in Sweden, probably other countries too)

1.5-2	MHz FM	Illegal cordless phones
46.5-47	MHz FM	Illegal cordless phones
78-80	MHz FM	Police, Firedepartement, Customs, Ambulance...
90-110	MHz WFM	Radio channels (P1, P2, P3...)
118-137 MHz AM	Aeroplanes
155-162 MHz FM	Marine
400-468 MHz FM	Various communication
410-412	MHz FM	Police (larger cities)
420-468	MHz FM	Cellular phones
890-960 MHz FM	Cellular and cordless phones

NMT (Nordic Mobilephone Net) is analogue and can be picked up with a scanner without any extra equipment.

Receiving digital signals

While scanning you will probably come across digital signals. They sound kind of modem like. Modem stands for MOdulator/DEModulator. To make sense of the digital signals you have to get them into a computer. An interface between the scanner and the computer is needed, a demodulator. Demodulators can be ordered from Pervisell.

You also need software for the computer to receive the signals. What software depends on what format the digital signals have. Some common formats are:

CW		Telegraph (morse code)
RTTY		Format for sending text (RadioTeleTYpe).
AMTOR		RTTY with error correction (also called navtex,arq,fec...)
FACSIMILE	Format for sending fax images
SSTV		Radio Television
POCSAG		Post Office Code Standardization Advisory (Minicall messages)

HAMCOM is a great program that deals with most of the formats above. To receive POCSAG messages you need another program, PD (Pocsag Decoder). Both programs can be downloaded from Pervisell.

In Sweden minicall messages are sent on 161.4375 and 169.8 MHz (pocsag). There are 2 types of minicall messages, numeric and alpha. Numeric is numbers only and alpha is text messages. Numeric minicalls are used like person seekers, mostly telephone numbers. Alpha minicalls are used by the police, taxi, companies... Alpha minicall messages are also supported by Lotus Notes (used by many companies).

Last updated 1997-07-18 by LordB