Police radio comms in the post war years

[williamwright]

Does anyone have an details? Frequencies, modulation, tx powers, etc?

Bill

[Brian Gaff (Sofa)]

Were they not all on the area we now use for fm up at the top end. Some of
my earliest memories were of my father with a single valve super regeneritve
receiver he knocked up from junk that could listen to them. They seemed to
use both nbfm and am, but the fire folk were down at the bottom end of the
fm band and they seemed to use am most of the time.

Of course in the USA they used frequencies around the Band 1 TV frequencies
and in the 30meg region, as you could hear those here when the conditions
were right just like you could cb.
Not many radios covered those spectrums, but My dad modified some to do it.
Nowadays of course radios could receive huge ranges of frequencies in multi
modes as they are software based devices.

Now we have the radios, all the interesting traffic is encrypted digital.
Brian

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"williamwright" <wrights...@f2s.com> wrote in message
news:i3hbh7...@mid.individual.net...

[R. Mark Clayton]

On Friday, 11 December 2020 at 13:46:18 UTC, wrights...@aol.com wrote:
> Does anyone have an details? Frequencies, modulation, tx powers, etc?
>
> Bill

A long time ago they used channels in the upper broadcast FM band, which my old valve Philips FM (~1959) radio used to pick up without difficulty even though the police modulation was quite narrow band AM. Actually listening was an offence.

These were moved to around 140MHz, but forget where. Transceivers were normally in vehicles and the base covered a large area - often the whole force area. There were portable ones identifiable by their long whip aerials. Normally the base transmitted beeps when receiving, so that other users did not break in. During chases the base would retransmit reception in "talk through", although some bases left this permanently enabled. Code names were used for police stations to thwart casual eavesdroppers.

Personal radios were on ~450MHz. most PC's had one by the mid 1980's. They were smaller with a much shorter aerial and normally covered just a division or two.

Depending on location forces switch over to [encrypted] TETRA (GMP in 2002), so criminals [or the merely nosey] can no longer tune in, although I daresay one could detect usage nearby from signal strength.

Obviously more sophisticated radios would have been used by the DPG and anti-terrorism branches.

[Jim Lesurf]

In article <i3hbh7...@mid.individual.net>, williamwright

<wrights...@f2s.com> wrote:
> Does anyone have an details? Frequencies, modulation, tx powers, etc?

I can recall them being a pest for using part of Band II. 8-]

Then seeing the kerfuffle over TETRA. Went to a public meeting on that and
had my first encounter with the kinds of crazy conspiracy theories people
who are clueless about science can fall for.

Jim

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Audio Misc http://www.audiomisc.co.uk/index.html

[NY]

"R. Mark Clayton" <notya...@gmail.com> wrote in message
news:e02ff9a6-8b29-4379...@googlegroups.com...

I hadn't realised that car radios and personal radios used completely
different frequencies. So the 100 MHz transmissions that we *didn't* listen
to were all to/from cars, and not also from personal radios?

Did they use any frequency-agile techniques during the 100 MHz period, or
was a given car normally on a fixed channel for a significant length of
time?

I remember when I was at university in the early 80s, there was a narrow,
rocky lane that separated my hall of residence from another. There was the
sound of a lot of sirens that went on for a while, so my mate turned on his
radio cassette to listen, and in amongst what sounded like a progress report
for a chase, we suddenly heard the name of this rocky lane mentioned. So we
looked out of the window and saw lots of blue lights coming from the right;
a few seconds later a beaten-up Cortina lurched down the lane, pursued by
several "jam butties". Then there was an ominous bang, followed by "suspect
has crashed - he's out of the car". SOmeone who was nearby said suspects had
flung their doors wide open in this narrow lane between high walls, realised
that they had blocked their escape route and could only run backwards into
the arms of the police.

[Brian Gaff (Sofa)]

Yes the ones round here went to 152 ish nbfm. Very easy to listen to just a
bit down from the marine vhf comms band in fact. I remember it was not
illegal to listen but to pass it on or act on information so received.

The Americans want to be able to hear their police at work so only the most
sensitive comms tend to be encrypted I gather.

Brian

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"R. Mark Clayton" <notya...@gmail.com> wrote in message
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[Brian Gaff (Sofa)]

They did use channels yes, but it was hard on an ordinary fm tuner to tell
that. It was too wide. Normally the big base stations were on thus
frequencies there were others for cars in other parts of the vhf spectrum.
When the scanners came out they were all over the place. Sad now everything
is digital and rather worrying since we pay their wages, I used to like
messages like 99 at Esher in 10 minuets.
Tea is brewing that meant.

Brian

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"NY" <m...@privacy.invalid> wrote in message
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[NY]

"Brian Gaff (Sofa)" <bri...@blueyonder.co.uk> wrote in message
news:rr0omi$lf6$1...@dont-email.me...

> Yes the ones round here went to 152 ish nbfm. Very easy to listen to just
> a bit down from the marine vhf comms band in fact. I remember it was not
> illegal to listen but to pass it on or act on information so received.

When did the police move away from 100 MHz, in relation to when VHF/FM
radios became common in cars? In other words, how likely was it that someone
being pursued would be able to listen in to the police reports of the chase
and use those to take avoiding action? OK, the armed robbers (etc) could
have a dedicated scanner, but if they were caught with it, they might have a
hard time explaining it and "inferences might be drawn", whereas an ordinary
VHF/FM radio would be "standard" in some/all cars and so not incriminating.

I remember buying a VHF radio for my 1988 VW Golf when I bought it in the
early 90s, so I'd say that VHF radios were not standard items by then, even
in my Golf which was a GL spec, so not a base model. I *think* my 1993 Golf
had one as a standard factory fitting, and certainly my 1997 Peugeot 306
(and all cars since then) have had them. Hard to remember back to the days
of a manual tuning dial, and mechanical presets which had far too little
reproducibility to be useful for VHF where tuning has to be spot-on: 50 kHz
(0.05 MHz) either side is ropy and 100 kHz (0.1 MHz) either side is dead air
which puts the radio into audio muting.

[Max Demian]

On 11/12/2020 15:02, Jim Lesurf wrote:
> In article <i3hbh7...@mid.individual.net>, williamwright
> <wrights...@f2s.com> wrote:
>> Does anyone have an details? Frequencies, modulation, tx powers, etc?
>
> I can recall them being a pest for using part of Band II. 8-]

Another "pest" was that some FM radios were made that stopped at 100 MHz
so they couldn't receive stations that used the higher frequencies when
the police stopped using FM.

--
Max Demian

[Indy Jess John]

I still have a radio where the FM range only goes up to 104MHz. It is
not much use when most of the programmes I want to listen to are off the
end of the dial. It has a lovely tone though so is still good for Radio3
concerts.

Jim

[Woody]

Lets just clarify this all.

Police transmissions were in P-band with base at 100-104 and mobiles on
79-84MHz AM. You could hear them on an FM radio by slope detection where
the radio was off-tuned such that it was out of limiting it would
demodulate the audio. They were 25KHz channel spacing from about 1974
with the county boundary changes.
Fire were AM on 71 base Tx and 82 or thereabouts mobile Tx.

Then IMSMC WARC under pressure from the broadcasters required that the
UK should make the whole of the 88-108 FM band available which they did
in two steps. First 97-101 was cleared and the Police moved to either
152/143MHz or 154/147MHz but apart from Lancs and possibly the Met they
stayed AM.
Police also used the 450-470 band for portables with varying 'odd'
spacings. For instance they had events channels on 450/464 with a 14MHz
spacing, but most of their working channels were 451-453 on a 13.5MHz
spacing all of which were base Tx low. Heliplod were initially
137MHz-ish AM but eventually moved elsewhere.
They also had some open single frequency channels around 455, and SB and
(mainly) DS used encrypted radios made by Racal(?) in the same area.

Frequencies around 106-107 with 138-139 were mainly used by fuel and
power - gas, electricity, etc - and they too were AM. They were moved to
139/148 and most of them went FM and/or trunked.

Then along came the mess called Airwave which was/still is 380-385 and
390-395 on 10MHz spacing. The Airwave contracts were supposed to be for
10 years to be replaced by something (initially undefined) using a
non-proprietry system (i.e. not a version of Tetra.)

The ESMCP (Emergency Services Mobile Communications Project) went out to
tender about five years aggo with the intent of using 4G technology. O2
and EE were both initially in the frame but O2 pulled out leaving EE to
take the contract, then found they would have to install something like
380+ new sites as the Project required geographical and not population
coverage. Most of those sites were in Wales, the North of England and
Scotland. The first Airwave contract started expiring about three years
ago but the HO instructed they would have to be extended as EE would not
be able to supply a working system until this year, and as I remember it
that has now been extended to I think 2023. Many of the extra sites are
quite obvious being a white stick co-linear aerial top-mounted on a
25-30ft steel pole at the roadside. The Register is a good site to watch
what is happening.....

HTH

[Woody]

That was nothing to do with the frequency band Jim. Most of the earlier
VHF/FM radios had big/proper loudspeakers in them which had a wider
audio bandwidth and were less stressed and thus lower distortion. I
remember we had a Perdio four-band which was about 12" wide by 8" high
by 3" thick and had a 8x5" speaker!

[Brian Gregory]

Well obviously.

And rather insulting to suggest Indy Jess John didn't know that.

--
Brian Gregory (in England).

[Brian Gregory]

On 11/12/2020 21:35, Brian Gaff (Sofa) wrote:
> Yes the ones round here went to 152 ish nbfm. Very easy to listen to just a
> bit down from the marine vhf comms band in fact. I remember it was not
> illegal to listen but to pass it on or act on information so received.

I'm pretty certain it was always illegal to listen in but obviously in
practice nobody got in trouble unless they did something stupid with
what they heard like turning up to rubber neck at a big accident or fire.

[Indy Jess John]

On 12/12/2020 01:41, Brian Gregory wrote:

> Well obviously.
>
> And rather insulting to suggest Indy Jess John didn't know that.
>

I would rather be told something I already know than not be told at all
and not find out something I didn't know.
No complaints from me!

Jim

[Ian Jackson]

In message <i3ilse...@mid.individual.net>, Brian Gregory
<void-invalid...@email.invalid> writes

I think the reason it was illegal to listen was (and still is) that, in
the UK, you need a licence (or licence-free or other authorisation) to
use any part of the radio spectrum above 8(?)kHz (? Google required).

We are allowed to receive broadcast TV signals (for which we need a
licence) and broadcast radio signals (for which we no longer need a
licence). There are also some other radio signals that we are allowed to
receive - for example, radio amateurs - which were, I'm pretty sure, at
one time specifically mentioned in the radio and TV licences. And IIRC,
listening to CB signals was never specifically permitted unless you had
a CB transmitting licence (although it IS now, as you no longer need a
CB licence).

However, as for other radio transmissions, unless you have a licence or
other authorisation, you are not legally allowed to listen to or make
use of them. And if you do happen to listen to them, you must not reveal
to anyone any information you heard except (if my memory serves me
correctly) a duly authorised officer if The Crown). [Well, something
like that!]
--
Ian

[Brian Gaff (Sofa)]

It may still be in the act, but if it were really true all those magazines
like short wave news Practical wireless and the like would have had their
content censored, and they did not, so like a lot of old legislation its
been made invalid by means of the powers that be having allowed it. You need
to remember that in the times when the Wireless telegraphy act was being
written there was a lot of agro between European countries still.
After all you could and still can buy radios like the Icom 8600, which is
about 6 inches from my elbow as I type, which has a range from 100 Khz to
2ghz multi mode.
It could, if you really wanted to go to the trouble have adaptors for many
digital modes or indeed be interfaced to a computer for digital processing.
It is only the encryption that stops yyou listening in. In the US Mayors
like to actually allow their citizens to hear the police at work, so they
are often on the internet. One must obviously say that they will use more
secure connections for sensitive information of course.Often looking up
suspect details here used to only be allowed by a channel change, presumably
to a digital channel or whatever the system was back then Even so you could
still often hear the police forgetting to do this and the name and address
being given over plain fm.

Mobile phones. Back during the Falklands war, Most mobile phones were still
analogue. So one day the bloc from the foreign office we used to hear a lot
ont't telly was zooming up theA3 just past the Tolworth interchange, and I
was listening on my scanner and we got the whole saga of the Belgrano being
discussed on how to make it sound like a legitimate target to the public.
spin doctoring in the production stage.

It was a sad day when mobiles went digital. Just above 1ghz was fun in those
days. Who remembers the 999Mhz CB Band, supposedly the bees knees of CB? It
was expensive to buy the kit and had no range at all. No wonder it was
closed some years ago.
Now of course we have spot frequencies used by walkie talkie devices in the
uhf band, often used by crane drivers and their eyes on the ground and the
general public to keep track of one another, which you can pick up from
supermarkets. Hardly private, most seem to be nbfm. We have some at the
blind lawn bowls club to stop all the shouting of clock positions for the
bowlers on the green.
Lots moor of course, talkback channels from the broadcasters, one year
heard Sue Barker running a scam tennis challenge on the two male producers,
she made 50 quid out of challenging them to play they em both against her at
the same time. I'm sure she would deny the thing, but hustling was a good
name for it.

You can still hear that sort of thing at nearby events like Wimbledon and
Epsom. Increasingly though it, too is going digital. though the engineers
and presenters don't like thd latency and the sudden drop outs rather than
just hissing signals.

Question, why are the on site production centres which are one assumes on
trucks and caravans, called Scanners?

Brian

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"Ian Jackson" <ianREMOVET...@g3ohx.co.uk> wrote in message
news:6gNauyEn...@brattleho.plus.com...

[Roderick Stewart]

On Fri, 11 Dec 2020 15:02:53 +0000 (GMT), Jim Lesurf
<no...@audiomisc.co.uk> wrote:

>In article <i3hbh7...@mid.individual.net>, williamwright
><wrights...@f2s.com> wrote:
>> Does anyone have an details? Frequencies, modulation, tx powers, etc?
>
>I can recall them being a pest for using part of Band II. 8-]

I remember it too. I always thought it was an utterly crazy thing to
do to put this sort of thing in the middle of a broadcast band, but it
was sometimes fun to listen to. It was distorted and sometimes you
could hear several conversations at once, because a hi-fi FM receiver
wasn't really meant for it, but by fiddling the tuning control it was
usually possible to make out what was being said.

Rod.

[Jim Lesurf]

In article <rr102l$h1g$1...@dont-email.me>, Woody <harro...@ntlworld.com>
wrote:

> That was nothing to do with the frequency band Jim. Most of the earlier
> VHF/FM radios had big/proper loudspeakers in them which had a wider
> audio bandwidth and were less stressed and thus lower distortion.

Similarly old models (and cheap ones!) might have a wider IF bandwidth. Not
good for rejecting adjacent/alternate channels, but *good* for getting
lower distortion and a flatter audio bandwidth. Sensible in the days when
the band wasn't crowded. But may be unusuable today in many areas of the
UK.

[Max Demian]

There's a story that the police sent out reports of a UFO landing
somewhere and then went and arrested all the UFO nuts who turned up.
Sounds unlikely. It's pointless making something easy to do, that people
might want to do, illegal. Like unconventional sex.

--
Max Demian

[Chris Youlden]

On 11/12/2020 13:46, williamwright wrote:
> Does anyone have an details? Frequencies, modulation, tx powers, etc?
>
> Bill

A small bit of info here, but not vey much unfortunately.

<https://british-police-history.uk/f/nottinghamshire-radio>

--

Chris

[Mark Carver]

On 12/12/2020 10:47, Roderick Stewart wrote:
>
> I remember it too. I always thought it was an utterly crazy thing to
> do to put this sort of thing in the middle of a broadcast band, but it
> was sometimes fun to listen to. It was distorted and sometimes you
> could hear several conversations at once, because a hi-fi FM receiver
> wasn't really meant for it, but by fiddling the tuning control it was
> usually possible to make out what was being said.
>
>

It's because the transmissions were AM and not FM. If you mistuned
slightly, 'edge detection' enabled you to sort of hear what was being said.

It was easier with a cheap radio, because the AM rejection was worse
than a top flight tuner.

[Mark Carver]

On 11/12/2020 23:37, Woody wrote:
> Lets just clarify this all.
>
> Police transmissions were in P-band with base at 100-104 and mobiles
> on 79-84MHz AM.

They were lower down too.

I remember trying to listen to LBC on 97.3 when it opened in 1973, and
the police were stamping over the top of them.
Though I was in Hampshire, out of area, so presumably the Met in London
had been cleared away from 97-98 ish in time for LBC's opening ?

Wasn't there also a problem on Merseyside when Radio 1 (98.9) launched
from Holme Moss on 1989 ?

[charles]

In article <mk79tf130o3eij3s9...@4ax.com>,

Roderick Stewart <rj...@escapetime.myzen.co.uk> wrote:
> On Fri, 11 Dec 2020 15:02:53 +0000 (GMT), Jim Lesurf
> <no...@audiomisc.co.uk> wrote:

> >In article <i3hbh7...@mid.individual.net>, williamwright
> ><wrights...@f2s.com> wrote:
> >> Does anyone have an details? Frequencies, modulation, tx powers, etc?
> >
> >I can recall them being a pest for using part of Band II. 8-]

> I remember it too. I always thought it was an utterly crazy thing to
> do to put this sort of thing in the middle of a broadcast band,

It wasn't "Put in the middle of a broadcast band." tne emergency services
were there before it became a broadcast band.

> but it
> was sometimes fun to listen to. It was distorted and sometimes you
> could hear several conversations at once, because a hi-fi FM receiver
> wasn't really meant for it, but by fiddling the tuning control it was
> usually possible to make out what was being said.

> Rod.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

[Ian Jackson]

In message <mk79tf130o3eij3s9...@4ax.com>, Roderick
Stewart <rj...@escapetime.myzen.co.uk> writes

>On Fri, 11 Dec 2020 15:02:53 +0000 (GMT), Jim Lesurf
><no...@audiomisc.co.uk> wrote:
>
>>In article <i3hbh7...@mid.individual.net>, williamwright
>><wrights...@f2s.com> wrote:
>>> Does anyone have an details? Frequencies, modulation, tx powers, etc?
>>
>>I can recall them being a pest for using part of Band II. 8-]
>
>I remember it too. I always thought it was an utterly crazy thing to
>do to put this sort of thing in the middle of a broadcast band

Think 'chicken' and 'egg'. I suspect that the police were there first.
The original UK FM band was only 88 to 94.6MHz (although even the first
receivers probably did tune somewhat higher - 104MHz being typical).

>, but it
>was sometimes fun to listen to. It was distorted and sometimes you
>could hear several conversations at once, because a hi-fi FM receiver
>wasn't really meant for it, but by fiddling the tuning control it was
>usually possible to make out what was being said.
>

Indeed!
--
Ian

[Woody]

I corrected the second reference to the frequencies but missed this one.
P-band was 79-101.5 and the base Tx was in the range 97-101 although the
allocated section of Band II was 97.7-102.3. It was supposed to have
been cleared by 1990 although I suspect that most users moved a while
before that!

[Woody]

Another interesting read is www.dtels.org.uk which will tell you much
about the technical side and the people at the old Home Office
Department of Telecommunications or DTels.

They were based at Horseferry House in London but were moved to a brand
new HQ at Ruddington near Nottingham in 1993 and sold off for £1 to NTL
in 1994.

[charles]

In article <rr2phc$ccn$2...@dont-email.me>,

some of it stayed in London - the bit that was close to Waterloo Station.
(Old GPO building, now part of Kings College). I used to go to meetings
there on a regular basis - that bit moved to Docklands and was the target
of the IRA dockland's bomb. [not many people know that]

[Mark Carver]

On 12/12/2020 15:29, Ian Jackson wrote:
>
> Think 'chicken' and 'egg'. I suspect that the police were there first.
> The original UK FM band was only 88 to 94.6MHz (although even the
> first receivers probably did tune somewhat higher - 104MHz being
> typical).

The first move higher than 94.6 was the Third Prog from Wenvoe in March
1959 on 96.8 (still used today to beam BBC Cymru all over the west of
England !)

[R. Mark Clayton]

As stated there were man portable [large] radios on the ~150MHz band. Don't know about then they were on ~100MHZ.

In a large op' an officer accompanying the superintendant would carry one.

>
> Did they use any frequency-agile techniques during the 100 MHz period, or
> was a given car normally on a fixed channel for a significant length of
> time?

No frequencies were fixed, and whom they belonged to fairly well known, however if there was a special op' or major incident then they would use a different frequency styled 'silver' or 'gold', which before scanners would be difficult to find.

>
> I remember when I was at university in the early 80s, there was a narrow,
> rocky lane that separated my hall of residence from another. There was the
> sound of a lot of sirens that went on for a while, so my mate turned on his
> radio cassette to listen, and in amongst what sounded like a progress report
> for a chase, we suddenly heard the name of this rocky lane mentioned. So we
> looked out of the window and saw lots of blue lights coming from the right;
> a few seconds later a beaten-up Cortina lurched down the lane, pursued by
> several "jam butties". Then there was an ominous bang, followed by "suspect
> has crashed - he's out of the car". SOmeone who was nearby said suspects had
> flung their doors wide open in this narrow lane between high walls, realised
> that they had blocked their escape route and could only run backwards into
> the arms of the police.

I enjoyed a similar incident. Some Pakistani neighbours had been suffering from thieving etc. and had formed a reception committee of an impromptu cricket team made up of their friends and neighbours (too many batsmen IMO). They were practising in one of their front gardens. As I got off a bus nearby I noticed two young men climb over the back garden wall, so I rushed over to tell them. Soon the noise of one of them on a garage roof could be heard - couple of batsmen readied themselves to "welcome" him. Fortunately for the miscreant the police, who had been following them arrived and the lucky thief dropped into the arms of a PC and was promptly arrested.

[R. Mark Clayton]

>SNIP

UHF CB was on 1MHz of bandwidth at 937MHz, the usual stuff was on ~27MHz AM.

There were no UK cellular mobile phones until 1/1/85, although there were mobile radio telephones (0G) and by the 1980's fully automatic ones (e.g. Storno). Cars fitted with a connected one commanded a premium of ~£2k used until cellular arrived.

[Cellular] Mobile phones stayed analogue (1G - [E]TACS) on 900MHz band until ~1993 when GSM (2G) arrived and the Orange and 121 networks started on 1G8Hz band.
IIRC the send and receive channels on 1G were 45MHz apart, but one could hear the whole conversation from the base station side. BTC Cellnet and Vodafone switched off their 1G service around 2000.

[NY]

"Ian Jackson" <ianREMOVET...@g3ohx.co.uk> wrote in message

news:WGNxn6Gl...@brattleho.plus.com...

> In message <mk79tf130o3eij3s9...@4ax.com>, Roderick Stewart
> <rj...@escapetime.myzen.co.uk> writes
>>On Fri, 11 Dec 2020 15:02:53 +0000 (GMT), Jim Lesurf
>><no...@audiomisc.co.uk> wrote:
>>
>>>In article <i3hbh7...@mid.individual.net>, williamwright
>>><wrights...@f2s.com> wrote:
>>>> Does anyone have an details? Frequencies, modulation, tx powers, etc?
>>>
>>>I can recall them being a pest for using part of Band II. 8-]
>>
>>I remember it too. I always thought it was an utterly crazy thing to
>>do to put this sort of thing in the middle of a broadcast band
>
> Think 'chicken' and 'egg'. I suspect that the police were there first. The
> original UK FM band was only 88 to 94.6MHz (although even the first
> receivers probably did tune somewhat higher - 104MHz being typical).

Did mainland Europe and USA use different frequencies for their
police/fire/ambulance comms, given that their VHF radios tuned to the full
88-108 range? Or did they initially only use the frequencies below 100 MHz
for radio stations?

What was/is below 88 MHz that prevented it being used for radio stations,
and what's above 108? How did the exact limits arise?

94.6 as an initial upper limit is very low: basically space for R2, R3 and
R4 - and not even local BBC stations. By the time I can remember VHF (late
60s) most of the space up to 100 was being used for local BBC, and later a
few ILR stations in the 1970s (eg LBC on 97.3). I can't remember: did the
top end of the band start to be used for broadcast radio, even before the
police stopped using 100?


I bet the British police weren't at all pleased to find that radios were
being widely sold which were capable of receiving (some of) their
transmissions because they were designed for countries where the full 88-108
was free for broadcast radio. ;-)

[NY]

"R. Mark Clayton" <notya...@gmail.com> wrote in message

news:7681acbe-4107-4515...@googlegroups.com...

LOL. I do like to hear of villains getting their comeuppance like this. I
still smile at the thought (in my story) of the thieves flinging their doors
wide open so they hit the boundary walls of the alley, and then realising
that this blocks their escape *forwards* away from the police, so they only
way is backwards into the arms of the police.

[NY]

"R. Mark Clayton" <notya...@gmail.com> wrote in message

news:c8c3d30a-a4a5-40de...@googlegroups.com...

> There were no UK cellular mobile phones until 1/1/85, although there were
> mobile radio telephones (0G) and by the 1980's fully automatic ones (e.g.
> Storno). Cars fitted with a connected one commanded a premium of ~£2k
> used until cellular arrived.
>
> [Cellular] Mobile phones stayed analogue (1G - [E]TACS) on 900MHz band
> until ~1993 when GSM (2G) arrived and the Orange and 121 networks started
> on 1G8Hz band.
> IIRC the send and receive channels on 1G were 45MHz apart, but one could
> hear the whole conversation from the base station side. BTC Cellnet and
> Vodafone switched off their 1G service around 2000.

I can remember the first time I saw a mobile phone, some time between 1986
and 1989 (I was at a conference when I worked at my first employer). It was
a large wooden box, a bit like the old acoustic couplers to allow terminals
to communicate with a central computer via an ordinary phone handset. This
had a big rubber duck aerial on top and a GPO-style telephone handset that
lived in recesses in the top of the box when not being used. It had a
shoulder strap for carrying it around. I *think* it may have had a dial
rather than push buttons.

We've progressed a bit since - to a phone that is small and thin enough to
put in a trouser pocket and which can do far more than just making/receiving
phone calls. We still haven't solved the problem of getting 100% reliable
phone calls and/or low-speed (up to 1 Mbps) internet in urban areas. I can
understand coverage being patchy in isolated rural areas -
cost-effectiveness of masts becomes an issue - but in a town centre where
there will be lots of usage, there is no excuse for not having sufficient
masts.

[Woody]

88-108 or Band II was/is defined by WARC - the World Administrative
Radio Conference. It is they also that set DAB into the top end of
BandIII, and added L-Band around 1500MHz for DAB also, etc etc.

C-band or 108-136 is exclusively for aircraft, part of B-band 156-162 is
for Marine use - these all worldwide. Bands IV and V were (and still
are) almost exclusively TV: there used to be a gap in channels 34-38
around 580-620MHz where long range radar sat but that has now moved to
much higher frequencies and is almost all SSR transponding radar.

Outside that countries can to a large extent chose what bands they want
to use for what purpose provided they fall within internationally
defined limits/bands. The Eastern Bloc used to use 76-83MHz for
broadcast radio. The US used to use frequencies around 35MHz for mobile
radio especially the police and so it goes on.

For interest
https://www.ofcom.org.uk/__data/assets/pdf_file/0016/103309/uk-fat-2017.pdf
will show you the UK frequency bandplan almost from dc to light.

[Brian Gaff (Sofa)]

Last year some older equipment was used during the London Marathon, as I
heard decidedly Police like chatter up at 152Mhz in plain old nbfm, Also
there were some private security people up at uhf too.

Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
bri...@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!

"charles" <cha...@candehope.me.uk> wrote in message
news:58ddc789...@candehope.me.uk...

[Mark Carver]

On 12/12/2020 19:09, NY wrote:
>
>
> 94.6 as an initial upper limit is very low: basically space for R2, R3
> and R4 - and not even local BBC stations. By the time I can remember
> VHF (late 60s) most of the space up to 100 was being used for local
> BBC, and later a few ILR stations in the 1970s (eg LBC on 97.3). I
> can't remember: did the top end of the band start to be used for
> broadcast radio, even before the police stopped using 100?

Yes, 102-105 range was the first to be opened up in 1983. In fact Signal
Radio in Stoke-on-Trent who were on 104.3 had a tag line, 'We're on the
Right Side of the Police' !

[Roderick Stewart]

Before the upper band was opened, all the main stations used the same
grouping and frequency spacing (2.2MHz) between the three programmes -
the Light Programme, the Third Programme, and the Home Service (in
that order) and most of them still do.

It's clearly some sort of Grand Plan that never got fully implemented
in the manner envisaged by whoever planned it, probably thinking that
three national programmes would be all we would ever need. The
subsequent addition of extra services has really messed it up.

One thing the standard spacing makes possible is a tuner that doesn't
need a conventional tuning control - just a three way switch. Our
school actually had one of these, made by Rogers I think. Most people
then would have been accustomed to tuning a radio for maximum volume,
but presetting it for the local transmitter and only requiring them to
use a switch would have made it unnecessary to re-educate them for
tuning FM receivers for minimum distortion.

Rod.

[charles]

In article <12rbtft14jidlpbgm...@4ax.com>,

Roderick Stewart <rj...@escapetime.myzen.co.uk> wrote:
> On Sun, 13 Dec 2020 08:55:37 +0000, Mark Carver
> <mark....@invalid.invalid> wrote:

> >On 12/12/2020 19:09, NY wrote:
> >>
> >>
> >> 94.6 as an initial upper limit is very low: basically space for R2, R3
> >> and R4 - and not even local BBC stations. By the time I can remember
> >> VHF (late 60s) most of the space up to 100 was being used for local
> >> BBC, and later a few ILR stations in the 1970s (eg LBC on 97.3). I
> >> can't remember: did the top end of the band start to be used for
> >> broadcast radio, even before the police stopped using 100?
> >
> >Yes, 102-105 range was the first to be opened up in 1983. In fact Signal
> >Radio in Stoke-on-Trent who were on 104.3 had a tag line, 'We're on the
> >Right Side of the Police' !

> Before the upper band was opened, all the main stations used the same
> grouping and frequency spacing (2.2MHz) between the three programmes -
> the Light Programme, the Third Programme, and the Home Service (in
> that order) and most of them still do.

> It's clearly some sort of Grand Plan that never got fully implemented
> in the manner envisaged by whoever planned it, probably thinking that
> three national programmes would be all we would ever need. The
> subsequent addition of extra services has really messed it up.

The 'grand plan' was simply trying to fit the 3 services (Home, Light &
Third) into the frequencies that the GPO made available. Some areas, such
as Wiltshire, never really got a service.

[NY]

"Roderick Stewart" <rj...@escapetime.myzen.co.uk> wrote in message
news:12rbtft14jidlpbgm...@4ax.com...

> Before the upper band was opened, all the main stations used the same
> grouping and frequency spacing (2.2MHz) between the three programmes -
> the Light Programme, the Third Programme, and the Home Service (in
> that order) and most of them still do.

I must admit I'd never studied the relationship between the R2/R3/R4
frequencies for a given transmitter. I hadn't realised there was always the
same spacing.

That reminds me: I really *must* sort out the aerial for my car radio.
Around the Bridlington area, I'm lucky to get *any* reception below 100 MHz
(so no R2/R3/R4) and reception above 100 is very noisy, even on the high
ground that ought to have clear sight of Bilsdale, Emley Moor, Oliver's
Mount and Belmont, or whichever high ground has a VHF transmitter. Probably
a duff aerial cable, which is going to be a pig to sort out - how the F do
you thread a new cable from the roof aerial to the back of the dashboard? I
suppose the headlining can be removed somehow, but it's perilously close to
the mini airbags in the A pillars. If I had a spare radio I'd try that with
the existing cable to make sure it's not the tuner that's f*cked. I had a
good look at the radio end of the cable when I removed the radio to fit a
hands-free phone kit, and there was no obvious kinking or shorting of braid
to inner conductor.

[Woody]

For the record even Radio 1 complies in most cases with the 'standard'
spacing. It is usually 9.6MHz above Radio 2 (except for example Belmont
and Wrotham) and even Classic is in most cases 11.8MHz above Radio 2.
[Don't know reason for Wrotham, but Belmont <should> be 88.7 for R2 but
was moved up 100KHz to stop mutual interference with BBC Sheffield on 88.6.]

[Ian Jackson]

In message <12rbtft14jidlpbgm...@4ax.com>, Roderick
Stewart <rj...@escapetime.myzen.co.uk> writes

I don't really get how the 'same grouping and frequency spacing' makes
any difference. Even with a three-way switch, each station would have to
be tuned in individually, and that could be to any frequency in the
band. I think I had one portable with a six press-button station
selector, and each button could be pre-set to any station (with a
tweaking capacitor or, more likely, if varicap tuned, a potentiometer).
--
Ian

[charles]

poor connection of aerial to cable?

[Brian Gregory]

It's all explained here: https://preview.tinyurl.com/yblrs3uf

--
Brian Gregory (in England).

[Brian Gregory]

On 12/12/2020 19:38, Woody wrote:
> For interest
> https://www.ofcom.org.uk/__data/assets/pdf_file/0016/103309/uk-fat-2017.pdf
> will show you the UK frequency bandplan almost from dc to light.
>

Latest version web page only:
http://static.ofcom.org.uk/static/spectrum/fat.html

[R. Mark Clayton]

On Saturday, 12 December 2020 at 19:25:40 UTC, NY wrote:
> "R. Mark Clayton" <notya...@gmail.com> wrote in message
> news:c8c3d30a-a4a5-40de...@googlegroups.com...
> > There were no UK cellular mobile phones until 1/1/85, although there were
> > mobile radio telephones (0G) and by the 1980's fully automatic ones (e.g.
> > Storno). Cars fitted with a connected one commanded a premium of ~£2k
> > used until cellular arrived.
> >
> > [Cellular] Mobile phones stayed analogue (1G - [E]TACS) on 900MHz band
> > until ~1993 when GSM (2G) arrived and the Orange and 121 networks started
> > on 1G8Hz band.
> > IIRC the send and receive channels on 1G were 45MHz apart, but one could
> > hear the whole conversation from the base station side. BTC Cellnet and
> > Vodafone switched off their 1G service around 2000.
> I can remember the first time I saw a mobile phone, some time between 1986
> and 1989 (I was at a conference when I worked at my first employer). It was
> a large wooden box, a bit like the old acoustic couplers to allow terminals
> to communicate with a central computer via an ordinary phone handset. This
> had a big rubber duck aerial on top and a GPO-style telephone handset that
> lived in recesses in the top of the box when not being used. It had a
> shoulder strap for carrying it around. I *think* it may have had a dial
> rather than push buttons.

You may be recalling the GPO's 1970's modems. Most of the first cellular phones were car phones, however there was a transportable a bit like what you describe.

The first portable I saw was a Motorola DynaTAC 8000x in 1985. We were buying lots of their chips so they arranged to bring one to see. It was still very clunky, with roughly the dimensions and weight of a brick, however in early 1986 Technophone brought out one that (as advertised) really would fit in a shirt pocket and run all day on a charge so I bought one (£2,000+VAT!). I used it for six years before replacing it with a Motorola Elite. It was on loan to MOSI from 2006 - 2016.

>
> We've progressed a bit since - to a phone that is small and thin enough to
> put in a trouser pocket and which can do far more than just making/receiving
> phone calls. We still haven't solved the problem of getting 100% reliable
> phone calls and/or low-speed (up to 1 Mbps) internet in urban areas. I can
> understand coverage being patchy in isolated rural areas -
> cost-effectiveness of masts becomes an issue - but in a town centre where
> there will be lots of usage, there is no excuse for not having sufficient
> masts.

Signals penetrate poorly in to old stone or steel framed buildings buildings, but look up Wi-Fi calling... Where I live my Nokia N79 (2009) got 7M2bps, my N8 (2011)14M4bps and my first LTE enable phone (2017) 76Mbps out of the box.

[Max Demian]

On 12/12/2020 15:29, Ian Jackson wrote:

> In message <mk79tf130o3eij3s9...@4ax.com>, Roderick
> Stewart <rj...@escapetime.myzen.co.uk> writes
>> On Fri, 11 Dec 2020 15:02:53 +0000 (GMT), Jim Lesurf
>> <no...@audiomisc.co.uk> wrote:
>>
>>> In article <i3hbh7...@mid.individual.net>, williamwright
>>> <wrights...@f2s.com> wrote:
>>>> Does anyone have an details? Frequencies, modulation, tx powers, etc?
>>>
>>> I can recall them being a pest for using part of Band II. 8-]
>>
>> I remember it too. I always thought it was an utterly crazy thing to
>> do to put this sort of thing in the middle of a broadcast band
>
> Think 'chicken' and 'egg'. I suspect that the police were there first.
> The original UK FM band was only 88 to 94.6MHz (although even the first
> receivers probably did tune somewhat higher - 104MHz being typical).

My parents' Hacker was like that:
https://www.ebay.co.uk/c/17010075958

--
Max Demian

[Max Demian]

What do you mean Wiltshire never got a VHF/FM service?

--
Max Demian

[Mark Carver]

Not  a medium power one for the national services no, Naish Hill near
Devizes would have probably have been the site, but the frequencies in
the national sub-band simply weren't available because the transmitter
would have interfered with other bordering national service
transmitters. Instead Wiltshire is peppered with a clutch of small relays.
Although Naish Hill did  get used for both the ILR and BBC Wiltshire
local radio stations, and it's a fairly important DAB site.

[Mark Carver]

On 13/12/2020 11:45, Woody wrote:
>
> For the record even Radio 1 complies in most cases with the 'standard'
> spacing. It is usually 9.6MHz above Radio 2 (except for example
> Belmont and Wrotham) and even Classic is in most cases 11.8MHz above
> Radio 2.
> [Don't know reason for Wrotham, but Belmont <should> be 88.7 for R2
> but was moved up 100KHz to stop mutual interference with BBC Sheffield
> on 88.6.]
>

R1 Wrotham is 100kHz 'high because of a service on the continent, can't
remember where. It also has to run at 120kW rather than 240kW
R1 Rowridge is also 100kHz high, as is Classic FM at North Hessary Tor.
Again, to avoid clashes over the channel.

[NY]

"charles" <cha...@candehope.me.uk> wrote in message

news:58de3235...@candehope.me.uk...

Yes, that as well. It's going to be one or more of:

- radio plug to cable

- cable

- aerial to cable

With the connections at either end being more likely than cable itself (eg
kinks).

I'll see if I can remove the headlining and see if there's access to the
aerial and its connection to the cable. I'm 90% confident that the
cable-to-radio-plug end has already been checked the other year.

[Woody]

Its not just Wiltshire. Go into E or NE Somerset and your choice for
main station FM is Wenvoe. Bristol has Ilchester Crescent and Bath has
Batheaston but only covering a relatively small areas. There are some
local stations and a LOT of DAB on Mendip which might make up for some
of it but go anywhere from Frome to Shepton Mallet to Wells or south
from Frome towards the A30 and national FM leaves a lot to be desired.

[Woody]

Does that mean that we can put them back where they should be after the
end of this year? ;-))

[Mark Carver]

The Beeb wanted to use Mendip, Waltham, and Hannington for national FM,
but there was no room in the 88-94.6 sub-band

For a while in the 90s it seemed like there might have been 105.0 to
107.9 allocated for national radio overspill, (Five services using
600kHz separation) but instead 105 to 106.9 got used for regional
commercial radio, and 107.0 to 107.9 for small town ILR.

[charles]

In article <i3n8gm...@mid.individual.net>,

Not quite true as none of these sites existed when the FM band was planned.
But they might havbe been built earlier.

> For a while in the 90s it seemed like there might have been 105.0 to
> 107.9 allocated for national radio overspill, (Five services using
> 600kHz separation) but instead 105 to 106.9 got used for regional
> commercial radio, and 107.0 to 107.9 for small town ILR.

[Mark Carver]

On 13/12/2020 20:33, charles wrote:
> In article <i3n8gm...@mid.individual.net>,
> Mark Carver <mark....@invalid.invalid> wrote:
> eb wanted to use Mendip, Waltham, and Hannington for national FM,
>> but there was no room in the 88-94.6 sub-band
> Not quite true as none of these sites existed when the FM band was planned.
> But they might havbe been built earlier.

They were planned in the 80s, not the 50s. Hence the proposal for them
to use the 105-108 band that was due to become available in 1995

[Roderick Stewart]

On Sun, 13 Dec 2020 11:45:19 +0000, Woody <harro...@ntlworld.com>
wrote:

>> Before the upper band was opened, all the main stations used the same
>> grouping and frequency spacing (2.2MHz) between the three programmes -
>> the Light Programme, the Third Programme, and the Home Service (in
>> that order) and most of them still do.
>>

[...]

>
>For the record even Radio 1 complies in most cases with the 'standard'
>spacing. It is usually 9.6MHz above Radio 2 (except for example Belmont
>and Wrotham) and even Classic is in most cases 11.8MHz above Radio 2.
>[Don't know reason for Wrotham, but Belmont <should> be 88.7 for R2 but
>was moved up 100KHz to stop mutual interference with BBC Sheffield on 88.6.]

I don't understand what you mean by "standard spacing". Neither 9.6MHz
nor 11.8MHz is a multiple of the spacing of 2.2MHz between the three
original national programmes.

Rod.

[Roderick Stewart]

On Sun, 13 Dec 2020 11:45:53 +0000, Ian Jackson
<ianREMOVET...@g3ohx.co.uk> wrote:

>>One thing the standard spacing makes possible is a tuner that doesn't
>>need a conventional tuning control - just a three way switch. Our
>>school actually had one of these, made by Rogers I think. Most people
>>then would have been accustomed to tuning a radio for maximum volume,
>>but presetting it for the local transmitter and only requiring them to
>>use a switch would have made it unnecessary to re-educate them for
>>tuning FM receivers for minimum distortion.
>>
>I don't really get how the 'same grouping and frequency spacing' makes
>any difference. Even with a three-way switch, each station would have to
>be tuned in individually, and that could be to any frequency in the
>band. I think I had one portable with a six press-button station
>selector, and each button could be pre-set to any station (with a
>tweaking capacitor or, more likely, if varicap tuned, a potentiometer).

The design of the Rogers tuner was, if I recall, such that there was a
single internal tuning adjustment to set it for a paricular
transmitter, and the front panel tuning control was a three position
rotary wafer switch with, I think some extra components between its
contacts. There was no simple way to adjust the stations individually.
To install this tuner for a different transmitter you'd only have to
make one adjustment and all three tuning positions would be moved
together. This could only work if the three staions in every region
had the same grouping and spacing, and if we'd only ever had the Light
Programme, the Third Programme and the Home Service, and in that
order, it would still work today. Somebody must have thought it was a
good idea.

Rod.

[Roderick Stewart]

I had a Hacker FM portable that only went up to 101MHz. This was
disappointing, but my choice was because it had a large wooden case of
the same design as used for other radios in the range which also had
AM bands. Because of the missing circuit boards in the FM-only version
there was lots of empty space in which it was possible to add a stereo
decoder and a pair of amplifiers for headphones, and a mains power
supply. I could use it as a portable or as a hi-fi tuner.

Rod.

[Mark Carver]

On 14/12/2020 08:24, Roderick Stewart wrote:
>
>> For the record even Radio 1 complies in most cases with the 'standard'
>> spacing. It is usually 9.6MHz above Radio 2 (except for example Belmont
>> and Wrotham) and even Classic is in most cases 11.8MHz above Radio 2.
>> [Don't know reason for Wrotham, but Belmont <should> be 88.7 for R2 but
>> was moved up 100KHz to stop mutual interference with BBC Sheffield on 88.6.]
> I don't understand what you mean by "standard spacing". Neither 9.6MHz
> nor 11.8MHz is a multiple of the spacing of 2.2MHz between the three
> original national programmes.

No, but Radio 1 and Classic FM follow the same 2.2 MHz 'template' in
their sub bands, so what Woody is saying is you can determine their
frequencies in a given area by adding 9.6 and 11.8 to Radio 2's allocation

By the way, national FM stations in Eire also follow the same pattern

[NY]

"Roderick Stewart" <rj...@escapetime.myzen.co.uk> wrote in message

news:na9etf1vdqjirkln1...@4ax.com...

>>> Think 'chicken' and 'egg'. I suspect that the police were there first.
>>> The original UK FM band was only 88 to 94.6MHz (although even the first
>>> receivers probably did tune somewhat higher - 104MHz being typical).

My grandparents had a large radio from the 1950s (or maybe very early 60s):
valves rather than transistor, "magic eye" tuning aid. And that could
receive VHF. It could pick up the police so it evidently went up as far as
100 MHz, even if it didn't go beyond to the full 108 MHz extent of the band.

>>My parents' Hacker was like that:
>>https://www.ebay.co.uk/c/17010075958
>
> I had a Hacker FM portable that only went up to 101MHz. This was
> disappointing, but my choice was because it had a large wooden case of
> the same design as used for other radios in the range which also had
> AM bands. Because of the missing circuit boards in the FM-only version
> there was lots of empty space in which it was possible to add a stereo
> decoder and a pair of amplifiers for headphones, and a mains power
> supply. I could use it as a portable or as a hi-fi tuner.

Thinking of radios with unusual tuning ranges, I remember one of my or my
parents' radios could receive slightly higher frequencies on the LW band or
slightly lower on the MW band that most others, so I could pick up a few
aircraft NDBs (non-directional beacons for navigation). I remember hearing
the repeated morse code and thinking (when I was a lad) that it was secret
agents communicating with each other. It wasn't until I started playing MS
Flight Simulator and learned about NDBs that I realised that the morse that
I'd been mis-hearing (*) was the three letters of a local beacon.

(*) I think I inserted a space where there wasn't one, converting one letter
with a lot of dots and dashes into two letters with fewer of them.

[NY]

"Mark Carver" <mark....@invalid.invalid> wrote in message
news:i3ong2...@mid.individual.net...

Ah, so you're saying that R2, 3, 4 are 2.2 apart from each other, then
there's a larger gap, followed by R1 and Classic which are 2.2 apart. Are
you saying that the larger gap (5.5 from R4) is a fixed size for all/most
transmitters?

eg

90.0
92.2
94.4

99.6
101.8


Why was it that analogue TV transmitters didn't have equal spacing between
stations? They were a fixed but *unequal* spacing - eg for Emley Moor

41
44
47
51

so spacings of 3, 3, 4 channels (24, 24, 32 MHz) apart.

Likewise (for Oxford)

53
57
60
63

4, 3, 3

[Mark Carver]

The spacing for analogue UHF was to avoid a spacing of 9 channels,
because (9 x 8 MHz) = 72 MHz which was roughly double the IF used in
domestic tuners, so it was to avoid spurious images. There was also a
rule regarding a spacing  of 5 channels for similar reasons

One of the factors that made the co existence of DTT with analogue
possible on adjacent and these taboo channels was the specification that
DTT receivers had good image rejection performance (and adjacent channel).

The rule for FM planning was to avoid separation of 10.7 MHz (the
standard IF for FM tuners) . Although there are now many examples of
situations where that's been broken, but up until the 80s it was adhered to.

The Americans to this day only use allocations that are 'odd numbers' 
88.1, 88.3, 88.5, etc so that any IF image is pushed out of harm's way
to an 'even' allocation, and actually looking at the first FM
allocations we used in the 50s and 60s here the same rule seemed to apply ?

[charles]

In article <rr7b5e$as9$1...@dont-email.me>,

because the TV receivers around at the time were not particularly good at
separating out the channels. take any channel 'n'; you couldn't use n-1,
n+1 and n+9. So most transmitters used n, n+3, n+6 and n+10

[Jim Lesurf]

In article <rr79mm$1ck$1...@dont-email.me>, NY <m...@privacy.invalid> wrote:
> Thinking of radios with unusual tuning ranges, I remember one of my or
> my parents' radios could receive slightly higher frequencies on the LW
> band or slightly lower on the MW band that most others,

The Armstrong 600 series AM tuner covers both LW and MW as being one band,
and thus also can be used to tune to the frequencies in between.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

[Mark Carver]

On 14/12/2020 09:59, Jim Lesurf wrote:
> In article <rr79mm$1ck$1...@dont-email.me>, NY <m...@privacy.invalid> wrote:
>> Thinking of radios with unusual tuning ranges, I remember one of my or
>> my parents' radios could receive slightly higher frequencies on the LW
>> band or slightly lower on the MW band that most others,
> The Armstrong 600 series AM tuner covers both LW and MW as being one band,
> and thus also can be used to tune to the frequencies in between.
>
>

So have a number of car radios I've had this century

[charles]

In article <58deab0...@audiomisc.co.uk>,

Jim Lesurf <no...@audiomisc.co.uk> wrote:
> In article <rr79mm$1ck$1...@dont-email.me>, NY <m...@privacy.invalid> wrote:
> > Thinking of radios with unusual tuning ranges, I remember one of my or
> > my parents' radios could receive slightly higher frequencies on the LW
> > band or slightly lower on the MW band that most others,

> The Armstrong 600 series AM tuner covers both LW and MW as being one band,
> and thus also can be used to tune to the frequencies in between.

> Jim

I wonder who the designer was?

[charles]

In article <i3pc42...@mid.individual.net>,

I can remmeber one which hit a microswitch at the end of MW travel and went
to a fixed tuned station on LW.

[NY]

"charles" <cha...@candehope.me.uk> wrote in message

news:58deb04a...@candehope.me.uk...

>> Why was it that analogue TV transmitters didn't have equal spacing
>> between
>> stations? They were a fixed but *unequal* spacing - eg for Emley Moor
>
>> 41
>> 44
>> 47
>> 51
>
>> so spacings of 3, 3, 4 channels (24, 24, 32 MHz) apart.
>
>> Likewise (for Oxford)
>
>> 53
>> 57
>> 60
>> 63
>
>> 4, 3, 3
>
> because the TV receivers around at the time were not particularly good at
> separating out the channels. take any channel 'n'; you couldn't use n-1,
> n+1 and n+9. So most transmitters used n, n+3, n+6 and n+10

I knew about poor discrimination in IF stages so I would have guessed that
n+1 and maybe n+2 would be prohibited. I hadn't realised that n+9 was a
problem as well.

And now we have channels (well, multiplexes) on n+1 (eg Belmont has PSB1 22,
COM5 23, PSB2 25, COM6 26) with no problem - presumably combination of a
sharper roll-off in the IF and the rejection of a weaker signal that's
interfering with a stronger one that digital gives you. Amazing what they
can get away with. I wonder whether we'll ever get the the stage of two
orthogonal aerials which are separately selectable, to give UHF 23
(horizontally polarised) and UHF 23 (vertically polarised)? ;-) After all,
it happens with satellite, though there are *very* few muxes where there's
an H and a V *on the same frequency*.

[NY]

"Mark Carver" <mark....@invalid.invalid> wrote in message

news:i3pc42...@mid.individual.net...

Never seen that. Some modern ones, with synthesiser tuning, have a single
"M" band which scans upwards from low-end LW to high-end MW, but jumps from
200+ (*) to 530 kHz as you scan or single-step.


(*) I forget what the upper limit is: the only thing I've ever used LW for
is R4 (LW) on 198 (or R2 a long time ago on 200), so I don't know what the
extremes of this band normally are for AM broadcasting.

[Brian Gregory]

It's all explained here: https://preview.tinyurl.com/yblrs3uf

--
Brian Gregory (in England).

[charles]

I remember seeing a cable service in SW London where there were carriers
every 300kHZ. Some HiFi tuners were unhappy.

[Brian Gregory]

On 14/12/2020 15:56, NY wrote:
> (*) I forget what the upper limit is: the only thing I've ever used LW
> for is R4 (LW) on 198 (or R2 a long time ago on 200), so I don't know
> what the extremes of this band normally are for AM broadcasting.

IIRC 279kHz is the last broadcast channel.

[Mark Carver]

On 14/12/2020 15:28, NY wrote:
>
> And now we have channels (well, multiplexes) on n+1 (eg Belmont has
> PSB1 22, COM5 23, PSB2 25, COM6 26) with no problem - presumably
> combination of a sharper roll-off in the IF and the rejection of a
> weaker signal that's interfering with a stronger one that digital
> gives you.

Modern tuners don't even have an IF, they are DSP based, so they use
Fourier mathematics to decode signals. That's how the Sky Q box can
record half a dozen channels at once, and how RDS car radios don't need
to vector away in 200ms bursts to try out alternative frequencies, and
is the essence of smart phone functionality

[Mark Carver]

On 14/12/2020 16:29, charles wrote:
>
> I remember seeing a cable service in SW London where there were carriers
> every 300kHZ. Some HiFi tuners were unhappy.
>

Back in the 70s, the broadcasters aimed for 800 kHz minimum separation
for FM radio transmissions in the same area, 300 kHz in adjacent areas.

That seems to have been relaxed these days to 400 kHz and 200kHz (though
there are some examples of 100 kHz for adjacent areas)

[Jim Lesurf]

In article <58dec787...@candehope.me.uk>, charles

<cha...@candehope.me.uk> wrote:
> In article <58deab0...@audiomisc.co.uk>, Jim Lesurf
> <no...@audiomisc.co.uk> wrote:
> > In article <rr79mm$1ck$1...@dont-email.me>, NY <m...@privacy.invalid> wrote:
> > > Thinking of radios with unusual tuning ranges, I remember one of my
> > > or my parents' radios could receive slightly higher frequencies on
> > > the LW band or slightly lower on the MW band that most others,

> > The Armstrong 600 series AM tuner covers both LW and MW as being one
> > band, and thus also can be used to tune to the frequencies in between.

> > Jim

> I wonder who the designer was?

Given the cue... :-) ...

Ted Rule (was G3FEW)
http://www.audiomisc.co.uk/Armstrong/500/500page3.html

Details of the tuner
http://www.audiomisc.co.uk/Armstrong/600/600faq2.html
http://www.audiomisc.co.uk/Armstrong/600/600page4.html

He is, at least when I last emailed him, still alive. But had to give up
being a radio enthusast due to failing hearing, etc. A number of his tuner
designs had novel (for their time) features.

JIm

[NY]

"Mark Carver" <mark....@invalid.invalid> wrote in message

news:i3r94c...@mid.individual.net...

Ah, I didn't know that. So would that mean a single DVB-T2 tuner could tune
to more than one multiplex so as to record, simultaneously, channels from
more than one mux? Or does the fact that none of my DVB-T tuners can tune to
more that one mux at the same time mean they don't use DSP?

I thought that RDS radios still had a second low-spec tuner that could try
alternative frequencies to work out whether one was better than the one that
the radio was currently tuned to, so as to decide whether to retune the main
high-spec tuner.

[Mark Carver]

On 15/12/2020 12:26, NY wrote:
> "Mark Carver" <mark....@invalid.invalid> wrote in message
> news:i3r94c...@mid.individual.net...
>> On 14/12/2020 15:28, NY wrote:
>>>
>>> And now we have channels (well, multiplexes) on n+1 (eg Belmont has
>>> PSB1 22, COM5 23, PSB2 25, COM6 26) with no problem - presumably
>>> combination of a sharper roll-off in the IF and the rejection of a
>>> weaker signal that's interfering with a stronger one that digital
>>> gives you.
>>
>> Modern tuners don't even have an IF, they are DSP based, so they use
>> Fourier mathematics to decode signals. That's how the Sky Q box can
>> record half a dozen channels at once, and how RDS car radios don't
>> need to vector away in 200ms bursts to try out alternative
>> frequencies, and is the essence of smart phone functionality
>
> Ah, I didn't know that. So would that mean a single DVB-T2 tuner could
> tune to more than one multiplex so as to record, simultaneously,
> channels from more than one mux? Or does the fact that none of my
> DVB-T tuners can tune to more that one mux at the same time mean they
> don't use DSP?

The latter I suspect

>
> I thought that RDS radios still had a second low-spec tuner that could
> try alternative frequencies to work out whether one was better than
> the one that the radio was currently tuned to, so as to decide whether
> to retune the main high-spec tuner.

30 years ago yes. Today, no. My present car can harvest all sorts of
stuff in the background, including sucking live TMC data for the sat nav
from the D1 DAB mux, and a rolling list of all other available FM and
DAB stations as I drive up or down the country, all while I'm listening
to another station.

And then off the back of that, there are SDR (Software Defined Radio)
radio receivers all over the world, that you can tune to to your heart's
content

Here's one in Bedford

http://remoteradio.changeip.org:8073/

[R. Mark Clayton]

Really - scanning through the FM band with a dipole 15m up gets me scores of stations within about a 100km radius. (The Pennines and capture effect limit anything beyond). With a few exceptions they all seem to be on 300kHz spacing.

[Mark Carver]

OK, well, I'll give some local examples.

Radio Berkshire   Reading  104.4
Radio Surrey       Guildford  104.6

Radio Berkshire  Hannington 104.1
Radio  Sussex     Reigate          104.0

Wessex FM    Bincombe Hill    97.2
Heart FM       Yeovil                   97.1

[spu...@isnotyourbuddy.co.uk]

On Tue, 15 Dec 2020 13:30:46 +0000
Mark Carver <mark....@invalid.invalid> wrote:
>On 15/12/2020 12:26, NY wrote:
>> I thought that RDS radios still had a second low-spec tuner that could
>> try alternative frequencies to work out whether one was better than
>> the one that the radio was currently tuned to, so as to decide whether
>> to retune the main high-spec tuner.
>
>30 years ago yes. Today, no. My present car can harvest all sorts of

Try 11 years ago. My FM/AM car radio noticably cuts out briefly when trying a
different frequency.

>stuff in the background, including sucking live TMC data for the sat nav
>from the D1 DAB mux, and a rolling list of all other available FM and
>DAB stations as I drive up or down the country, all while I'm listening
>to another station.
>
>And then off the back of that, there are SDR (Software Defined Radio)
>radio receivers all over the world, that you can tune to to your heart's
>content

Naturally there's no such thing as a free lunch and SDRs like any other
software heavy system suck power. That might be fine in a car tuner but you
wouldn't want one in a battery powered portable. As anyone who owns a DAB
portable knows, those things get through batteries like an alcoholic gets
through pints in a pub.

[Tweed]

Best not tell your mobile phone then....

[Mark Carver]

On 15/12/2020 14:13, Tweed wrote:
> Naturally there's no such thing as a free lunch and SDRs like any other
>> software heavy system suck power. That might be fine in a car tuner but you
>> wouldn't want one in a battery powered portable. As anyone who owns a DAB
>> portable knows, those things get through batteries like an alcoholic gets
>> through pints in a pub.
>>
>>
> Best not tell your mobile phone then....

Indeed. And why would you need to be worrying about dymanic data and
retuning info for a radio that sits at home ?!

[Tweed]

I wonder why DAB chipsets are still so power hungry? I fairly sure I could
listen to the “radio” via my mobile phone for much longer than I could run
a DAB radio on a similar capacity battery. Perhaps there’s just no money to
be made from it.

[spu...@isnotyourbuddy.co.uk]

Are you talking about smartphones that need to be charged every bloody day?

Good thing I have an old Nokia but even that doesn't last as long as a pair
of AAs in an FM portable.

[spu...@isnotyourbuddy.co.uk]

Streaming just piggybacks on the phone link which has to remain up all the
time anyway. Its not going to increase the battery usage much as its only
decoding the audio, not the entire radio band. Plus built in FM radios are
almost certainly a cheapo FM decoder circuit shoved in a corner somewhere.

[Jim Lesurf]

In article <i3rs47...@mid.individual.net>, Mark Carver

<mark....@invalid.invalid> wrote:
> > Ah, I didn't know that. So would that mean a single DVB-T2 tuner could
> > tune to more than one multiplex so as to record, simultaneously,
> > channels from more than one mux? Or does the fact that none of my
> > DVB-T tuners can tune to more that one mux at the same time mean they
> > don't use DSP?

> The latter I suspect

The SRD dongle I use for capture of DVB-T1/T2 will record an entire MUX.
But only one at a time.

Jim

[Brian Gregory]

On 15/12/2020 13:30, Mark Carver wrote:
> 30 years ago yes. Today, no. My present car can harvest all sorts of
> stuff in the background, including sucking live TMC data for the sat nav
> from the D1 DAB mux, and a rolling list of all other available FM and
> DAB stations as I drive up or down the country, all while I'm listening
> to another station.

I think you'll find that's still done by an extra tuner, or maybe more
than one extra tuner.

https://www.electronicproducts.com/an-introduction-to-automotive-sdr-2/

https://www.st.com/resource/en/data_brief/tda7707.pdf

[NY]

"Jim Lesurf" <no...@audiomisc.co.uk> wrote in message
news:58df56f...@audiomisc.co.uk...

> In article <i3rs47...@mid.individual.net>, Mark Carver
> <mark....@invalid.invalid> wrote:
>> > Ah, I didn't know that. So would that mean a single DVB-T2 tuner could
>> > tune to more than one multiplex so as to record, simultaneously,
>> > channels from more than one mux? Or does the fact that none of my
>> > DVB-T tuners can tune to more that one mux at the same time mean they
>> > don't use DSP?
>
>> The latter I suspect
>
> The SRD dongle I use for capture of DVB-T1/T2 will record an entire MUX.
> But only one at a time.

Yes, mine will do that. VLC (Media | Open Capture Device | Capture Mode =
TV-digital | Transponder frequency = <the mux frequency>) will play a whole
multiplex, from which you can choose any station (Playback | Programme |
<choose station>). If you press the red-dot record button it records the
whole multiplex.

When I used to use Windows Media Centre rather than NextPVR or TVHeadend,
WMC was unable to record two overlapping programmes *even if they were on
the same multiplex* so on occasions I used VLC to record the whole mux and
then extracted one programme then the other to separate .ts files with
VideoRedo.

At about 25 Mbps for a T1 mux, whole-mux file sizes were humungous ;-)



I've never (until now) heard of a single tuner that can record one or more
programmes from *different* multiplexes. But I can see how it could be done
"in software/firmware". I wonder what the practical limit is for the number
of different programmes from different muxes you can record simultaneously.
The ultimate would be a single device that could record all 7 multiplexes
;-)

[Mark Carver]

Very interesting, many thanks, yes, it does seem to suggest there are
still discrete tuners at the front end

[jon]

On Sat, 12 Dec 2020 19:38:21 +0000, Woody wrote:

> On Sat 12/12/2020 19:09, NY wrote:
>> "Ian Jackson" <ianREMOVET...@g3ohx.co.uk> wrote in message
>> news:WGNxn6Gl...@brattleho.plus.com...
>>> In message <mk79tf130o3eij3s9...@4ax.com>, Roderick
>>> Stewart <rj...@escapetime.myzen.co.uk> writes
>>>> On Fri, 11 Dec 2020 15:02:53 +0000 (GMT), Jim Lesurf
>>>> <no...@audiomisc.co.uk> wrote:
>>>>
>>>>> In article <i3hbh7...@mid.individual.net>, williamwright
>>>>> <wrights...@f2s.com> wrote:
>>>>>> Does anyone have an details? Frequencies, modulation, tx powers,
>>>>>> etc?
>>>>>
>>>>> I can recall them being a pest for using part of Band II. 8-]
>>>>
>>>> I remember it too. I always thought it was an utterly crazy thing to
>>>> do to put this sort of thing in the middle of a broadcast band
>>>
>>> Think 'chicken' and 'egg'. I suspect that the police were there first.
>>> The original UK FM band was only 88 to 94.6MHz (although even the
>>> first receivers probably did tune somewhat higher - 104MHz being
>>> typical).
>>
>> Did mainland Europe and USA use different frequencies for their
>> police/fire/ambulance comms, given that their VHF radios tuned to the
>> full 88-108 range? Or did they initially only use the frequencies below
>> 100 MHz for radio stations?
>>
>> What was/is below 88 MHz that prevented it being used for radio
>> stations, and what's above 108? How did the exact limits arise?
>>
>> 94.6 as an initial upper limit is very low: basically space for R2, R3
>> and R4 - and not even local BBC stations. By the time I can remember
>> VHF (late 60s) most of the space up to 100 was being used for local
>> BBC, and later a few ILR stations in the 1970s (eg LBC on 97.3). I
>> can't remember: did the top end of the band start to be used for
>> broadcast radio, even before the police stopped using 100?
>>
>>
>> I bet the British police weren't at all pleased to find that radios
>> were being widely sold which were capable of receiving (some of) their
>> transmissions because they were designed for countries where the full
>> 88-108 was free for broadcast radio. ;-)
>
>
> 88-108 or Band II was/is defined by WARC - the World Administrative
> Radio Conference. It is they also that set DAB into the top end of
> BandIII, and added L-Band around 1500MHz for DAB also, etc etc.
>
> C-band or 108-136 is exclusively for aircraft, part of B-band 156-162 is
> for Marine use - these all worldwide. Bands IV and V were (and still
> are) almost exclusively TV: there used to be a gap in channels 34-38
> around 580-620MHz where long range radar sat but that has now moved to
> much higher frequencies and is almost all SSR transponding radar.
>
> Outside that countries can to a large extent chose what bands they want
> to use for what purpose provided they fall within internationally
> defined limits/bands. The Eastern Bloc used to use 76-83MHz for
> broadcast radio. The US used to use frequencies around 35MHz for mobile
> radio especially the police and so it goes on.
>
> For interest
> https://www.ofcom.org.uk/__data/assets/pdf_file/0016/103309/uk-
fat-2017.pdf
> will show you the UK frequency bandplan almost from dc to light.


My B&O portable could receive aircraft (pilot to tower)together with my
Tandberg TR1010.....both went up to 108MHz

[R. Mark Clayton]

On Tuesday, 15 December 2020 at 14:13:40 UTC, Tweed wrote:
> <spu...@isnotyourbuddy.co.uk> wrote:
> > On Tue, 15 Dec 2020 13:30:46 +0000

SNIP

> >
> > Naturally there's no such thing as a free lunch and SDRs like any other
> > software heavy system suck power. That might be fine in a car tuner but you
> > wouldn't want one in a battery powered portable. As anyone who owns a DAB
> > portable knows, those things get through batteries like an alcoholic gets
> > through pints in a pub.
> >
> >
> Best not tell your mobile phone then....

Well indeed - I have one here, it runs three transceivers and one receiver 24/7 and gets through about 2Ahr per day recharging wirelessly for about two hours in the middle of the night. My tablet has a bigger battery and can manage the same for nearly a week.

Then there is my Kindle...

[Woody]

Unless you lived near the airport you were listening to you would only
ever hear the aircraft transmissions.

[David Woolley]

On 15/12/2020 12:26, NY wrote:

> Ah, I didn't know that. So would that mean a single DVB-T2 tuner could
> tune to more than one multiplex so as to record, simultaneously,
> channels from more than one mux? Or does the fact that none of my DVB-T
> tuners can tune to more that one mux at the same time mean they don't
> use DSP?

DVB-T2, like all COFDM receivers, will use DSP, as the coding scheme
require implementing 1,000s of closely spaced sub-carriers, which would
require 1,000s of high precision filters, if done in analogue, but is
easy for an FFT algorithm, in digital.

However, at least some, if not most, select the multiplex by more
analogue methods, or at least by the choice of sampling frequency.

Even for a fully digital one, decoding multiple multiplexes at once
would require more processing. If you look at the rules for my Humax,
it can simultaneously handle more than one channel in a multiplex, but
can only handle a maximum of two multiplexes.

Of course, as available processing power increases there is a trend to
do more in the digital signal processing.

[Mark Carver]

On 16/12/2020 12:46, Woody wrote:
>
> Unless you lived near the airport you were listening to you would only
> ever hear the aircraft transmissions.

I used to live about a mile from the end of Southampton Airport's
runway. Every morning I'd get the pilot's voice of the 06:55 flight to
Paris breaking through on my clock radio.
The plane was smack overhead my house at that instant. It was tuned to
96.7, so add 2x10.7 = 118.1 MHz ?

[Ian Jackson]

In message <i3usg4...@mid.individual.net>, Mark Carver
<mark....@invalid.invalid> writes

Almost certainly. Living 10 mile NW of Heathrow, when listening to LBC
on 97.3MHz on one of my radios I similarly sometimes used to get a
pilot's voice breaking through (usually when the plane was overhead, and
he was putting his foot down after reaching 3000').
--
Ian

[spu...@isnotyourbuddy.co.uk]

Given that aircraft use AM and an AM signal (particularly narrow band AM) on
any decent FM radio simply sounds like a kind of buzzing interference I'm
surprised you heard anything resembling a voice.

[Mark Carver]

Slope detection, and lousy AM rejection. The cheaper the radio, the
better the decoded audio was !

[Roderick Stewart]

On Thu, 17 Dec 2020 09:23:44 +0000, Mark Carver
<mark....@invalid.invalid> wrote:

>> Given that aircraft use AM and an AM signal (particularly narrow band AM) on
>> any decent FM radio simply sounds like a kind of buzzing interference I'm
>> surprised you heard anything resembling a voice.
>>
>Slope detection, and lousy AM rejection. The cheaper the radio, the
>better the decoded audio was !

Off tune and distorted. No good for music, but if it's speech you can
usually make out what's being said.

Rod.

[spu...@isnotyourbuddy.co.uk]

I thought slope detection only worked on an AM radio detecting FM, not the
other way around.