So if you've ever wondered what's beyond the dial on your ordinary radio, this is the page for you. Just be aware that you shouldn't tune in to anything private - if someone is talking loudly in the street and you can easily overhear, you still don't morally have the right to listen do you? If the vast amount of broadcasts and ham radio conversations aren't enough to amuse you (and the rest of what life in general has to offer) then that's quite sad. If I ever have time to switch on my receiver (to see what the propagation's like) the only bands I need to go to are amateur ones. And good music is much more satisfying. If you can find it.
In a decade or so there may not be all that much else to listen to anyway on current scanners, as almost all radio users head towards digital systems, often secure ones too. Maybe the spectrum will one day consist of just one system for mobile access to THE NET which provides for all possible communication needs - a load of buzzing noises wherever you tune, except for the long-established amateur bands. Then you scanner owners can relax, you won't be able to do anything illegal with them if you try - unless you decide to throw them through someone's window!
A scanner is already useless except for listening to the hams, airband, marine and a few businesses. Those who were only into the naughty stuff will have to adjust to a world where shopwatch schemes and the occasional search and rescue mission provide the only interest - or find another hobby. Those who are genuinely interested in radio will have no choice but to go down the amateur route.
I would say that if you have an interest in these matters, devote your energies now to Amateur Radio PLEASE! We need more activity in the bands. Amateur radio covers bands from Low Frequencies (with 2km wavelengths) to ultra-high micro-wave bands (wavelengths in millimetres) with modes ranging from good old-fashioned morse code (CW) to AM/FM speech (communications bandwidths) to advanced narrowband speech (Single Side Band) to Television (slow scan like FAX through to full motion/definition FMW broadcast quality) to digital/data modes like RTTY and Packet. Transmissions can be direct, fixed and mobile (and Maritime Mobile), via satellite, bent through the troposphere, bounced off various layers of charged particles in the upper atmosphere, or even bounced off the moon (EME), or shooting stars (MS)! And all for just 15 quid per year - bargain. Go on, prove you know what you're talking about, get a callsign soon. Even if you don't ever use it... See theOFCOM web-page info, or theRadio Society for Good Buddies site for more details, or theUK Ham Radio FAQ. And theG7KPF Quick Links. Join and support the RSGB too, it's a good idea as they do tend to negotiate new bands for us.
Here then, is my quick tour of the spectrum of 2012, with links to other sites where appropriate.
All information sourced from freely published books, magazines and web-sites (RA,ERO), without the need for a scanner, as part of an ongoing quest to figure out what lies beyond the broadcasting bands...
Amateur & CB - HF, 50, 70, 144, 430 MHz etc. Can be good, can be dull - you decide. You may listen.(The rules)
Aeronautical - "airband" - HF, 108-137 MHz. You may not listen, but it seems to be tolerated.
Maritime - HF, 156-163 MHz. Probably tolerated, but no listening unless licensed, and on-board.
...thou shalt NOT listen...
Low Power / Short Range Devices - Cordless telephones / headphones / microphones, remote control etc.
PMSE - SAB/SAP - when TV/radio/film/programme makers use radio. Managed byJFMG (2012 frequencies):
a) Radiomicrophones - carrying "programme audio" obviously,
b) Talkback - on-site comms (simplex or continous duplex) or wide-area comms back to base,
c) Links - mobile "programme audio" back to base, or Fixed links between sites.
Like the military and many low-power devices, theyseem to crop up all over the spectrum! However, some of theassignments in shared bands (mainly BBC) are to cease in 2000, leaving mostly primary bands.
As Bands I, III, IV and V are designated BROADCASTING it seems logical that broadcasters may also use these bands formics and comms either at UHF on locally unused "in-band" channels, or (also for links) in the VHF bands that are no longer used for broadcasting.
Around 174MHz is very popular for mics, as well as other parts ofBand III that coincide with French TV carriers and so are not used for PBR.
Note that JFMG also deal with Special Event short-term assignments for local comms, e.g. Ascot.
PMR - channels are allocated in all bands to different categories such as :
. National exclusive,
. Wide Area Shared "G3" - taxis "T1", despatch "H4" etc. - 30kms range,
. ...& Medical (ambulance service - high band)
.CBS (follow the link for Common Base channels),
. On-site shared - dual "C2" or single "O5" - 3km range max., why not use PMR446?!
. Suppliers Light (wasShort Term Hire) (up to 1 year), demo (28 days), "parking" (3 months), Test&Dev,
. specific uses i.e.Road Construction
.Simple UK Light (was 'UK General') "U3" - mobile only, anywhere in UK, 5W ERP max - Shared channels : 5 in low-band, 2 in mid-band, 5 in high-band, 3 at UHF.(in 2002 the UHF channels changed and various conditions too. No time limit now, so it's a good LICENSED replacement forSRBR and 446, 20 quid a year)
Which explains why that "spare channel" can't be used for anything else in your area!
Given that the number of users of PMR channels runs into tens of thousands(2003 report,2000 report, and1997 report), it would be quitefutile to attempt to list them all - it amazes me that publications even try.
Even worse, once a frequency/user tie-up makes it into print, no-one ever seems to doubt itsvalidity and it's often printed way after it ceased to be used!
Fair enough to list national allocations, the general type of use for a channel - but to tryand find EVERY assigment, EVERY taxi firm.... ho hum.
Military - various web pages will show that there is a world market for equipment operating in thebands such as HF, 30-87.5 (25kHz FM), 116-155 & 225-400 (25kHz AM), 470-512 etc. Note that whilst the odd Combat Nethere and there may be "in the clear" any serious tactical use would be very hard to find. Frequency hopping andscrambling are used - after all, would you want your country defended by forces that could be easily monitored?
Operational use (like PMR) for base security, training, Mil. Police, MOULD etc. involves fixed frequencies, and various books show that Low VHF, Low Band, Mid Band, 406.1-420 and UHF1 are heavily used for these purposes. There iscurrently a general move from VHF to UHF, and the use of a TETRA system is being considered.This type of radio traffic is still not to be listened to!
...thou shalt definitely NOT listen...
(2009 update: and now everything is digital you can't anyway!)
Public Telecomms - paging, mobile telephone/data - the reason why scanner manufacturers HAD to includecoverage of the 900MHz band (! there's nowt else up there to listen to). Eavesdropping on analoguemobile calls is quite rightly frowned upon.
Home Office for the Emergency Services - previous versions of this document did not mention these allocations,but as the bands are shown on OFCOM pages, and in various books, some are now included for the sake of clarity.Only the BANDS are shown, not actual frequencies in use. Do NOT listen in!
NOTE 2: Dots after a frequency signifies the start of a range, whereas a single spot frequency has no trailing dots- although this doesn't apply in the two-column section.Frequencies given relate to the center of the transmission (COFDM, FM, AM) (i.e. theunmodulated carrier with carrier-based systems such as FM/AM), or the absent carrier for SSB.
NOTE 3: Scanner folk often use the terms Simplex and Duplex wrongly to describe Single and Dual frequency systems.The term Simplex means taking turns to transmit, whether on one or more frequencies. The proper terms to use are S.F.S.(Single Frequency Simplex) and D.F.S (Dual..). Duplex only applies on telephone style systems where one party caninterupt the other. Even TT (Talk-Through; repeaters) is still simplex. I use the abbrev.s Single and Dual. Any time Ispecify "Split" generally implies D.F.S., and details are given as base freq.s, with the change in frequency in +/- MHzneeded to hear the mobile.
Even "Duplex" doesn't neccessarily mean two frequencies, new digital systems can rapidly take turns on the same freq. bytime-compressing the audio data-stream!
ASSUMING you have permission to listen...
S.F.S. and TT (repeaters) are obviously very easy to monitor with just one memory (or in manual mode) and "scan delay"isn't a problem - the longer the delay the better, as many radio users seem to need a few seconds to think of areply (TT "over" pips are generally a waste of time, most dimwits wait for the squelch crunch). This means conventionalscanners are fine for monitoring amateur, CB, airband, ship-shore-ship, some PMR etc.
Private D.F.S is more tricky, depending on whether the base transmits pips to let other mobiles know the channel is busy.True D.F.S. with no "busy signal" just requires two scan memories and no scan-delay, which not all scanners allow. With"busy-pips" you'll need to be just a little smarter to catch all the action,should you have permission. DareI suggest investing in a cheap-n-cheerful second receiver to take care of just the strong base freq.s while usingthe better set/antenna for the mobile side...
These difficulties could be quite easily overcome if the manufacturers thought just a teensy bit harder about the operationof their receivers. By the time they DO get such advances implemented, everything will be digital anyway!
NOTES: FM deviation and bandwidth :
Bandwidth = 2(PeakDeviation+HighestModulationFreq) ... this is Carson's Rule - a rule of thumb, but very close.For 3kHz maximum speech frequency comms :
BW= 2(5+3) = 16kHz (for 5kHz dev)
BW= 2(2.5+3) = 11kHz (for 2.5kHz dev)
"The -60 or -70dBc bandwidth is approximately twice the Carson bandwidth."
The modulation index is defined as the peak deviation divided by the highestmodulating frequncy. "This would be 5/3 for NBFM and 2.5/3 for the really narrowstuff. Modulation indexes under 1 don't really work that well, 5/3 is almost 2,and broadcast FM uses 75/15 or 5. It depends on the type of Signal-to-Noise Ratio you need."Note also that true FM uses pre-emphasis per octave from 300 to 3000Hz - which matches theeffect of Phase Modulation.