Radio 3 on 91.3 was nearly wiped out by Italian stations all over Band II 
here in Surrey this morning. Heard one French station, half a dozen Italian 
ones and something which sounded like Arabic.

Seems unusual to get reception from Italy yet very little from France.

Peter

PeterW wrote:
> Radio 3 on 91.3 was nearly wiped out by Italian stations all over Band II 
> here in Surrey this morning. Heard one French station, half a dozen Italian 
> ones and something which sounded like Arabic.
> 
> Seems unusual to get reception from Italy yet very little from France.

That occurs with 'sporadic-E' propagation - there's a skip zone of
nearer stations that don't come through because the angle of incidence
to the ionosphere is too high for the signal to be refracted back down
again.


-- 
Richard Lamont                        http://www.lamont.me.uk/

OpenPGP Key ID: 0xBD89BE41
Fingerprint: CE78 C285 1F97 0BDA 886D BA78 26D8 6C34 BD89 BE41

"PeterW"  wrote in message
news:Xns9ACF99B92BB69PeterWpublic@192.168.1.250...
> Radio 3 on 91.3 was nearly wiped out by Italian stations all over Band II
> here in Surrey this morning. Heard one French station, half a dozen
> Italian
> ones and something which sounded like Arabic.
>
> Seems unusual to get reception from Italy yet very little from France.

I heard that too. I was trying out a seventies portable radio and heard lots
of Italian stations around 88-89MHz. I didn't even have the aerial up, just
my finger on the telescopic, not that this sensitive and selective beast
needed it. From my recolection its usually Italian stations I hear when
conditions get like this. I didn't delve much into the conditions, but
expect if I tuned up to around Radio 1, I would have heard a few of the
French national networks. Didn't seem to affect UHF TV.

Graham

On Wed, 2 Jul 2008 14:06:36 +0000 (UTC), PeterW
 wrote:

>Radio 3 on 91.3 was nearly wiped out by Italian stations all over Band II 
>here in Surrey this morning. Heard one French station, half a dozen Italian 
>ones and something which sounded like Arabic.
>
>Seems unusual to get reception from Italy yet very little from France.
>
>Peter

Not sure if it's connected, but I experienced a lot of interference on
R4 - ariound 09:00 toaday travelling between J42 & J47 of the M4 and
oacross the north of the Gower peninsula
-- 
Cheers

Peter

The message 
from Peter Thomas  contains these words:

> Not sure if it's connected, but I experienced a lot of interference on
> R4 - ariound 09:00 toaday travelling between J42 & J47 of the M4 and
> oacross the north of the Gower peninsula
> -- 
Me too - driving from Swansea to Port Talbot, then back and up the A470
to Ebbw Vale, between 0800 and 0915, all the BBC stations were all over
the place, hissing, and dropping out, with other stations popping up
every time the signal dropped just before the point where you'd normally
get RDS hand-over.  I didn't hear much after that, but it was fine on
the way back around lunchtime.

Mike

"Mike Winson"  wrote in message 
news:3130303034353533486BC5EB19@zetnet.co.uk...
> The message 
> from Peter Thomas  contains these words:
>
>> Not sure if it's connected, but I experienced a lot of interference on
>> R4 - ariound 09:00 toaday travelling between J42 & J47 of the M4 and
>> oacross the north of the Gower peninsula
>> -- 
> Me too - driving from Swansea to Port Talbot, then back and up the A470
> to Ebbw Vale, between 0800 and 0915, all the BBC stations were all over
> the place, hissing, and dropping out, with other stations popping up
> every time the signal dropped just before the point where you'd normally
> get RDS hand-over.  I didn't hear much after that, but it was fine on
> the way back around lunchtime.

Yep, that is precisely what I would expect with the conditions I heard this 
morning. I'll miss all this when the dreaded day comes and they switch off 
Band II radio. I really think its such a backward step going to digital when 
we have such an excellent analogue radio system in place. Perhaps a dual 
system but not do away with our well tried and tested VHF FM system. This 
rush to digital is so narrow minded. When I see the day they change air 
traffic control communications to digital, then perhaps I'll concede the 
technology has matured enough, but I still won't be going on any planes 
around that time.

Graham

On Wed, 2 Jul 2008 18:16:11 +0100, Mike Winson
 wrote:

>The message 
>from Peter Thomas  contains these words:
>
>> Not sure if it's connected, but I experienced a lot of interference on
>> R4 - ariound 09:00 toaday travelling between J42 & J47 of the M4 and
>> oacross the north of the Gower peninsula
>> -- 
>Me too - driving from Swansea to Port Talbot, then back and up the A470
>to Ebbw Vale, between 0800 and 0915, all the BBC stations were all over
>the place, hissing, and dropping out, with other stations popping up
>every time the signal dropped just before the point where you'd normally
>get RDS hand-over.  I didn't hear much after that, but it was fine on
>the way back around lunchtime.
>
>Mike

There is an RDS handover point almost exactly at M4 J46, but the
reception was equally poor on both sides of this point this morning -
OK tonight though.

-- 
Cheers

Peter

"Graham"  wrote in message 
news:nMGdnTZy4JV8V_bVnZ2dnUVZ8hidnZ2d@posted.metronet...
>
> "Mike Winson"  wrote in message 
> news:3130303034353533486BC5EB19@zetnet.co.uk...
>> The message 
>> from Peter Thomas  contains these words:
>>
>>> Not sure if it's connected, but I experienced a lot of interference on
>>> R4 - ariound 09:00 toaday travelling between J42 & J47 of the M4 and
>>> oacross the north of the Gower peninsula
>>> -- 
>> Me too - driving from Swansea to Port Talbot, then back and up the A470
>> to Ebbw Vale, between 0800 and 0915, all the BBC stations were all over
>> the place, hissing, and dropping out, with other stations popping up
>> every time the signal dropped just before the point where you'd normally
>> get RDS hand-over.  I didn't hear much after that, but it was fine on
>> the way back around lunchtime.
>
> Yep, that is precisely what I would expect with the conditions I heard 
> this morning. I'll miss all this when the dreaded day comes and they 
> switch off Band II radio. I really think its such a backward step going to 
> digital when we have such an excellent analogue radio system in place. 
> Perhaps a dual system but not do away with our well tried and tested VHF 
> FM system. This rush to digital is so narrow minded. When I see the day 
> they change air traffic control communications to digital, then perhaps 
> I'll concede the technology has matured enough, but I still won't be going 
> on any planes around that time.

Never mind digital, Civil Aviation has yet to be convinced that FM
has any merit over good old fashioned AM


-- 
Graham

%Profound_observation%

In news:g4h3cr$a3c$1@registered.motzarella.org,
Graham.  typed, for some strange, unexplained reason:

[snip]

: Never mind digital, Civil Aviation has yet to be convinced that FM
: has any merit over good old fashioned AM

I suspect it's more a matter of cost. Imagine replacing every single 
transceiver in every single aircraft worldwide, plus all the base station 
equipment.

All at once.

I do rather like AM for communications though, however getting equipment 
for it on the amateur bands is becoming more difficult these days, not 
many Pye Westminsters left ;-)

Ivor

The message <g4h3cr$a3c$1@registered.motzarella.org>
from "Graham."  contains these words:

> >
> > Yep, that is precisely what I would expect with the conditions I heard 
> > this morning. I'll miss all this when the dreaded day comes and they 
> > switch off Band II radio. I really think its such a backward step
> > going to 
> > digital when we have such an excellent analogue radio system in place. 
> > Perhaps a dual system but not do away with our well tried and tested VHF 
> > FM system. This rush to digital is so narrow minded. When I see the day 
> > they change air traffic control communications to digital, then perhaps 
> > I'll concede the technology has matured enough, but I still won't be
> > going 
> > on any planes around that time.

> Never mind digital, Civil Aviation has yet to be convinced that FM
> has any merit over good old fashioned AM



Main ATC channels might still be VHF AM but quite a lot of information
is passed between air <> ground <> air using various data systems.  Many
airports are going to TETRA for their ground services.  There are
arguments about why they prefer to stay on AM (apart from inertia) which
I can't remember in detail but it is not a simple case of AM = bad, FM -
good.

The RAF and RN still use HF for their SAR helicopters but the Coastguard
use satellite comms (i.e. digital) with no HF on board.  if they want to
speak to Kinloss ARCC they just call them up on the phone.

I heard one plane trying to call Prestwick and unable to get them so he
had a message relayed through a passing Speedbird, Prestwick passed
their phone number so he could just call them on his mobile next time he
has problems.  So indirectly digital is creeping into ATC!

MB

In article <g4h3cr$a3c$1@registered.motzarella.org>,
	Graham. wrote:

> Never mind digital, Civil Aviation has yet to be convinced that FM
> has any merit over good old fashioned AM

They use SSB on HF. It has the advantage that two stations can be
calling at the same time on the same frequency, and they'll both be
heard. They might not be understood, but they'll be heard as two calls.

SSB requires less than a quarter of the power of AM for the same reach.
On VHF the reach is limited to line of sight and so the power
requirements are much lower, so there's little advantage to SSB
working.

-- 
Paul Martin

"Graham."  wrote in message 
news:g4h3cr$a3c$1@registered.motzarella.org...
>
> "Graham"  wrote in message 
> news:nMGdnTZy4JV8V_bVnZ2dnUVZ8hidnZ2d@posted.metronet...
>>
>> "Mike Winson"  wrote in message 
>> news:3130303034353533486BC5EB19@zetnet.co.uk...
>>> The message 
>>> from Peter Thomas  contains these words:
>>>
>>>> Not sure if it's connected, but I experienced a lot of interference on
>>>> R4 - ariound 09:00 toaday travelling between J42 & J47 of the M4 and
>>>> oacross the north of the Gower peninsula
>>>> -- 
>>> Me too - driving from Swansea to Port Talbot, then back and up the A470
>>> to Ebbw Vale, between 0800 and 0915, all the BBC stations were all over
>>> the place, hissing, and dropping out, with other stations popping up
>>> every time the signal dropped just before the point where you'd normally
>>> get RDS hand-over.  I didn't hear much after that, but it was fine on
>>> the way back around lunchtime.
>>
>> Yep, that is precisely what I would expect with the conditions I heard 
>> this morning. I'll miss all this when the dreaded day comes and they 
>> switch off Band II radio. I really think its such a backward step going 
>> to digital when we have such an excellent analogue radio system in place. 
>> Perhaps a dual system but not do away with our well tried and tested VHF 
>> FM system. This rush to digital is so narrow minded. When I see the day 
>> they change air traffic control communications to digital, then perhaps 
>> I'll concede the technology has matured enough, but I still won't be 
>> going on any planes around that time.
>
> Never mind digital, Civil Aviation has yet to be convinced that FM
> has any merit over good old fashioned AM
>
And for good reason

"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message 
news:6d2iomFfk6kU1@mid.individual.net...
> In news:g4h3cr$a3c$1@registered.motzarella.org,
> Graham.  typed, for some strange, unexplained reason:
>
> [snip]
>
> : Never mind digital, Civil Aviation has yet to be convinced that FM
> : has any merit over good old fashioned AM
>
> I suspect it's more a matter of cost. Imagine replacing every single
> transceiver in every single aircraft worldwide, plus all the base station
> equipment.
>
> All at once.
>
> I do rather like AM for communications though, however getting equipment
> for it on the amateur bands is becoming more difficult these days, not
> many Pye Westminsters left ;-)

There is good reason for using AM for aircraft communication, or rather good 
reason not to use FM. If two aircraft transmit at the same time its very 
obvious due to the hetrodyne and the controller knows instantly two aircraft 
were trying to talk to him.

Graham

"Graham"  wrote in message 
news:GtWdnYLBqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet...
>
> "Graham."  wrote in message 
> news:g4h3cr$a3c$1@registered.motzarella.org...
>>
>> "Graham"  wrote in message 
>> news:nMGdnTZy4JV8V_bVnZ2dnUVZ8hidnZ2d@posted.metronet...
>>>

God, following who said what in this thread is becoming confusing.....

In article <GtWdnb3BqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet>, Graham
 scribeth thus
>
>"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message 
>news:6d2iomFfk6kU1@mid.individual.net...
>> In news:g4h3cr$a3c$1@registered.motzarella.org,
>> Graham.  typed, for some strange, unexplained reason:
>>
>> [snip]
>>
>> : Never mind digital, Civil Aviation has yet to be convinced that FM
>> : has any merit over good old fashioned AM
>>
>> I suspect it's more a matter of cost. Imagine replacing every single
>> transceiver in every single aircraft worldwide, plus all the base station
>> equipment.
>>
>> All at once.
>>
>> I do rather like AM for communications though, however getting equipment
>> for it on the amateur bands is becoming more difficult these days, not
>> many Pye Westminsters left ;-)
>
>There is good reason for using AM for aircraft communication, or rather good 
>reason not to use FM. If two aircraft transmit at the same time its very 
>obvious due to the hetrodyne and the controller knows instantly two aircraft 
>were trying to talk to him.
>
>Graham 
>
>

You do get that effect on FM but not quite the same way. 

As others might have said theres a lorra radios out there and they ain't
cheap;!..
-- 
Tony Sayer

In article <3130303030373135486C23B048@invalid.invalid>, MB
<MB@invalid.invalid> scribeth thus
>The message <g4h3cr$a3c$1@registered.motzarella.org>
>from "Graham."  contains these words:
>
>> >
>> > Yep, that is precisely what I would expect with the conditions I heard 
>> > this morning. I'll miss all this when the dreaded day comes and they 
>> > switch off Band II radio. I really think its such a backward step
>> > going to 
>> > digital when we have such an excellent analogue radio system in place. 
>> > Perhaps a dual system but not do away with our well tried and tested VHF 
>> > FM system. This rush to digital is so narrow minded. When I see the day 
>> > they change air traffic control communications to digital, then perhaps 
>> > I'll concede the technology has matured enough, but I still won't be
>> > going 
>> > on any planes around that time.
>
>> Never mind digital, Civil Aviation has yet to be convinced that FM
>> has any merit over good old fashioned AM
>
>
>
>Main ATC channels might still be VHF AM but quite a lot of information
>is passed between air <> ground <> air using various data systems.  Many
>airports are going to TETRA for their ground services.  There are
>arguments about why they prefer to stay on AM (apart from inertia) which
>I can't remember in detail but it is not a simple case of AM = bad, FM -
>good.
>
>The RAF and RN still use HF for their SAR helicopters but the Coastguard
>use satellite comms (i.e. digital) with no HF on board.  if they want to
>speak to Kinloss ARCC they just call them up on the phone.
>
>I heard one plane trying to call Prestwick and unable to get them so he
>had a message relayed through a passing Speedbird, Prestwick passed
>their phone number so he could just call them on his mobile next time he
>has problems.  So indirectly digital is creeping into ATC!
>
>MB

Umm .... using mobiles in aircraft to contact ground based stations
isn't a very clever idea!..
-- 
Tony Sayer

"tony sayer"  wrote in message 
news:VmqWnlE9jJbIFwzp@bancom.co.uk...
> In article <GtWdnb3BqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet>, Graham
>  scribeth thus
>>
>>"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
>>news:6d2iomFfk6kU1@mid.individual.net...
>>> In news:g4h3cr$a3c$1@registered.motzarella.org,
>>> Graham.  typed, for some strange, unexplained reason:
>>>
>>> [snip]
>>>
>>> : Never mind digital, Civil Aviation has yet to be convinced that FM
>>> : has any merit over good old fashioned AM
>>>
>>> I suspect it's more a matter of cost. Imagine replacing every single
>>> transceiver in every single aircraft worldwide, plus all the base 
>>> station
>>> equipment.
>>>
>>> All at once.
>>>
>>> I do rather like AM for communications though, however getting equipment
>>> for it on the amateur bands is becoming more difficult these days, not
>>> many Pye Westminsters left ;-)
>>
>>There is good reason for using AM for aircraft communication, or rather 
>>good
>>reason not to use FM. If two aircraft transmit at the same time its very
>>obvious due to the hetrodyne and the controller knows instantly two 
>>aircraft
>>were trying to talk to him.
>>
>>Graham
>>
>>
>
> You do get that effect on FM but not quite the same way.

No where near as distinct as with AM, hence the advantage.

"tony sayer"  wrote in message 
news:WGdWfwEjlJbIFwwA@bancom.co.uk...
> In article <3130303030373135486C23B048@invalid.invalid>, MB
> <MB@invalid.invalid> scribeth thus
>>The message <g4h3cr$a3c$1@registered.motzarella.org>
>>from "Graham."  contains these words:
>>
>>> >
>>> > Yep, that is precisely what I would expect with the conditions I heard
>>> > this morning. I'll miss all this when the dreaded day comes and they
>>> > switch off Band II radio. I really think its such a backward step
>>> > going to
>>> > digital when we have such an excellent analogue radio system in place.
>>> > Perhaps a dual system but not do away with our well tried and tested 
>>> > VHF
>>> > FM system. This rush to digital is so narrow minded. When I see the 
>>> > day
>>> > they change air traffic control communications to digital, then 
>>> > perhaps
>>> > I'll concede the technology has matured enough, but I still won't be
>>> > going
>>> > on any planes around that time.
>>
>>> Never mind digital, Civil Aviation has yet to be convinced that FM
>>> has any merit over good old fashioned AM
>>
>>
>>
>>Main ATC channels might still be VHF AM but quite a lot of information
>>is passed between air <> ground <> air using various data systems.  Many
>>airports are going to TETRA for their ground services.  There are
>>arguments about why they prefer to stay on AM (apart from inertia) which
>>I can't remember in detail but it is not a simple case of AM = bad, FM -
>>good.
>>
>>The RAF and RN still use HF for their SAR helicopters but the Coastguard
>>use satellite comms (i.e. digital) with no HF on board.  if they want to
>>speak to Kinloss ARCC they just call them up on the phone.
>>
>>I heard one plane trying to call Prestwick and unable to get them so he
>>had a message relayed through a passing Speedbird, Prestwick passed
>>their phone number so he could just call them on his mobile next time he
>>has problems.  So indirectly digital is creeping into ATC!
>>
>>MB
>
> Umm .... using mobiles in aircraft to contact ground based stations
> isn't a very clever idea!..

I think there is a big difference to a pilot using a mobile compared to a 
bunch of tossers in the back yakking away on them randomly. For a start the 
pilot would instantly know if something went wrong or indicated incorrectly 
the moment he used the phone. Using it for getting info from the ground, 
compared to not having that info, its obviously a good move. The actual 
chances of a mobile interfering is very slight, but of course that does not 
mean we want yakkers in the back to start using lots of them at the same 
time. The mixing of signals and spurious signals created due to them all 
going at once would indeed make a risk of interference to radio equipment 
and possibly the aircraft avionics itself.

Graham

"Jerry" <INVALID@INVALID.INVALID> wrote in message 
news:g4i1l4$bck$1@registered.motzarella.org...
>
> "Graham"  wrote in message 
> news:GtWdnYLBqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet...
>>
>> "Graham."  wrote in message 
>> news:g4h3cr$a3c$1@registered.motzarella.org...
>>>
>>> "Graham"  wrote in message 
>>> news:nMGdnTZy4JV8V_bVnZ2dnUVZ8hidnZ2d@posted.metronet...
>>>>
>
> God, following who said what in this thread is becoming confusing.....

I could make it more difficult if you like and change my return address to 
the same as the other Graham. Oh, which one am I? I've lost track myself 
now. :-)))

Graham, I mean Graham... Err Doh!!

In article <dKidnXEgw8iFNPHVRVnytQA@posted.metronet>, Graham
 scribeth thus
>
>"tony sayer"  wrote in message 
>news:WGdWfwEjlJbIFwwA@bancom.co.uk...
>> In article <3130303030373135486C23B048@invalid.invalid>, MB
>> <MB@invalid.invalid> scribeth thus
>>>The message <g4h3cr$a3c$1@registered.motzarella.org>
>>>from "Graham."  contains these words:
>>>
>>>> >
>>>> > Yep, that is precisely what I would expect with the conditions I heard
>>>> > this morning. I'll miss all this when the dreaded day comes and they
>>>> > switch off Band II radio. I really think its such a backward step
>>>> > going to
>>>> > digital when we have such an excellent analogue radio system in place.
>>>> > Perhaps a dual system but not do away with our well tried and tested 
>>>> > VHF
>>>> > FM system. This rush to digital is so narrow minded. When I see the 
>>>> > day
>>>> > they change air traffic control communications to digital, then 
>>>> > perhaps
>>>> > I'll concede the technology has matured enough, but I still won't be
>>>> > going
>>>> > on any planes around that time.
>>>
>>>> Never mind digital, Civil Aviation has yet to be convinced that FM
>>>> has any merit over good old fashioned AM
>>>
>>>
>>>
>>>Main ATC channels might still be VHF AM but quite a lot of information
>>>is passed between air <> ground <> air using various data systems.  Many
>>>airports are going to TETRA for their ground services.  There are
>>>arguments about why they prefer to stay on AM (apart from inertia) which
>>>I can't remember in detail but it is not a simple case of AM = bad, FM -
>>>good.
>>>
>>>The RAF and RN still use HF for their SAR helicopters but the Coastguard
>>>use satellite comms (i.e. digital) with no HF on board.  if they want to
>>>speak to Kinloss ARCC they just call them up on the phone.
>>>
>>>I heard one plane trying to call Prestwick and unable to get them so he
>>>had a message relayed through a passing Speedbird, Prestwick passed
>>>their phone number so he could just call them on his mobile next time he
>>>has problems.  So indirectly digital is creeping into ATC!
>>>
>>>MB
>>
>> Umm .... using mobiles in aircraft to contact ground based stations
>> isn't a very clever idea!..
>
>I think there is a big difference to a pilot using a mobile compared to a 
>bunch of tossers in the back yakking away on them randomly. For a start the 
>pilot would instantly know if something went wrong or indicated incorrectly 
>the moment he used the phone. Using it for getting info from the ground, 
>compared to not having that info, its obviously a good move. The actual 
>chances of a mobile interfering is very slight, but of course that does not 
>mean we want yakkers in the back to start using lots of them at the same 
>time. The mixing of signals and spurious signals created due to them all 
>going at once would indeed make a risk of interference to radio equipment 
>and possibly the aircraft avionics itself.
>
>Graham 
>
>
Its nothing to do with tossers yakking and all that, its more about
frequency reuse among base stations on the ground. It wasn't planned to
have mobile units at umpteen thousand feet ....
-- 
Tony Sayer

"tony sayer"  wrote in message 
news:zEA$PrFXWLbIFw0z@bancom.co.uk...
> In article <dKidnXEgw8iFNPHVRVnytQA@posted.metronet>, Graham
>  scribeth thus
>>
>>"tony sayer"  wrote in message
>>news:WGdWfwEjlJbIFwwA@bancom.co.uk...
>>> In article <3130303030373135486C23B048@invalid.invalid>, MB
>>> <MB@invalid.invalid> scribeth thus
>>>>The message <g4h3cr$a3c$1@registered.motzarella.org>
>>>>from "Graham."  contains these words:
>>>>
>>>>> >
>>>>> > Yep, that is precisely what I would expect with the conditions I 
>>>>> > heard
>>>>> > this morning. I'll miss all this when the dreaded day comes and they
>>>>> > switch off Band II radio. I really think its such a backward step
>>>>> > going to
>>>>> > digital when we have such an excellent analogue radio system in 
>>>>> > place.
>>>>> > Perhaps a dual system but not do away with our well tried and tested
>>>>> > VHF
>>>>> > FM system. This rush to digital is so narrow minded. When I see the
>>>>> > day
>>>>> > they change air traffic control communications to digital, then
>>>>> > perhaps
>>>>> > I'll concede the technology has matured enough, but I still won't be
>>>>> > going
>>>>> > on any planes around that time.
>>>>
>>>>> Never mind digital, Civil Aviation has yet to be convinced that FM
>>>>> has any merit over good old fashioned AM
>>>>
>>>>
>>>>
>>>>Main ATC channels might still be VHF AM but quite a lot of information
>>>>is passed between air <> ground <> air using various data systems.  Many
>>>>airports are going to TETRA for their ground services.  There are
>>>>arguments about why they prefer to stay on AM (apart from inertia) which
>>>>I can't remember in detail but it is not a simple case of AM = bad, FM -
>>>>good.
>>>>
>>>>The RAF and RN still use HF for their SAR helicopters but the Coastguard
>>>>use satellite comms (i.e. digital) with no HF on board.  if they want to
>>>>speak to Kinloss ARCC they just call them up on the phone.
>>>>
>>>>I heard one plane trying to call Prestwick and unable to get them so he
>>>>had a message relayed through a passing Speedbird, Prestwick passed
>>>>their phone number so he could just call them on his mobile next time he
>>>>has problems.  So indirectly digital is creeping into ATC!
>>>>
>>>>MB
>>>
>>> Umm .... using mobiles in aircraft to contact ground based stations
>>> isn't a very clever idea!..
>>
>>I think there is a big difference to a pilot using a mobile compared to a
>>bunch of tossers in the back yakking away on them randomly. For a start 
>>the
>>pilot would instantly know if something went wrong or indicated 
>>incorrectly
>>the moment he used the phone. Using it for getting info from the ground,
>>compared to not having that info, its obviously a good move. The actual
>>chances of a mobile interfering is very slight, but of course that does 
>>not
>>mean we want yakkers in the back to start using lots of them at the same
>>time. The mixing of signals and spurious signals created due to them all
>>going at once would indeed make a risk of interference to radio equipment
>>and possibly the aircraft avionics itself.
>>
>>Graham
>>
>>
> Its nothing to do with tossers yakking and all that, its more about
> frequency reuse among base stations on the ground. It wasn't planned to
> have mobile units at umpteen thousand feet ....

Thats one reason, but the fact remains that intermodulation frequencies from 
many phones transmitting at once and within feet of each other is a big 
problem to the aircraft operation as the mixing products will also be very 
strong. Anyone with knowledge of RF knows how nasty that mixing will be in 
the front end of a receiver, not to mention the general field strength of 
any one phone, that could get into wiring and avionics.

Graham (nospamGraham, not privacy Graham :-)

The message 
from tony sayer  contains these words:

> Umm .... using mobiles in aircraft to contact ground based stations
> isn't a very clever idea!..


Depends if the aircraft is in the air.

MB

On Thu, 3 Jul 2008 11:25:22 +0100, Graham  wrote:

> I think there is a big difference to a pilot using a mobile compared to a 
> bunch of tossers in the back yakking away on them randomly. For a start the 
> pilot would instantly know if something went wrong or indicated incorrectly 
> the moment he used the phone. Using it for getting info from the ground, 
> compared to not having that info, its obviously a good move. The actual 
> chances of a mobile interfering is very slight, but of course that does not 
> mean we want yakkers in the back to start using lots of them at the same 
> time. The mixing of signals and spurious signals created due to them all 
> going at once would indeed make a risk of interference to radio equipment 
> and possibly the aircraft avionics itself.

Who said it was anything to do with interference to the systems on board
the aircraft? Have you any clue what else it might be? Obviously not.

"Paul Ratcliffe" <abuse@orac12.clara34.co56.uk78> wrote in message 
news:slrng6pf39.t94.abuse@news.pr.network...
> On Thu, 3 Jul 2008 11:25:22 +0100, Graham  wrote:
>
>> I think there is a big difference to a pilot using a mobile compared to a
>> bunch of tossers in the back yakking away on them randomly. For a start 
>> the
>> pilot would instantly know if something went wrong or indicated 
>> incorrectly
>> the moment he used the phone. Using it for getting info from the ground,
>> compared to not having that info, its obviously a good move. The actual
>> chances of a mobile interfering is very slight, but of course that does 
>> not
>> mean we want yakkers in the back to start using lots of them at the same
>> time. The mixing of signals and spurious signals created due to them all
>> going at once would indeed make a risk of interference to radio equipment
>> and possibly the aircraft avionics itself.
>
> Who said it was anything to do with interference to the systems on board
> the aircraft? Have you any clue what else it might be? Obviously not.

I don't know if anyone said anything about interference or not, but its a 
damn good reason not to have too much stray RF around close to aircraft 
systems. That is just logical (if you understand RF?).

Graham

"Paul Ratcliffe" <abuse@orac12.clara34.co56.uk78> wrote in message 
news:slrng6pf39.t94.abuse@news.pr.network...
> On Thu, 3 Jul 2008 11:25:22 +0100, Graham  wrote:
>
>> I think there is a big difference to a pilot using a mobile compared to a
>> bunch of tossers in the back yakking away on them randomly. For a start 
>> the
>> pilot would instantly know if something went wrong or indicated 
>> incorrectly
>> the moment he used the phone. Using it for getting info from the ground,
>> compared to not having that info, its obviously a good move. The actual
>> chances of a mobile interfering is very slight, but of course that does 
>> not
>> mean we want yakkers in the back to start using lots of them at the same
>> time. The mixing of signals and spurious signals created due to them all
>> going at once would indeed make a risk of interference to radio equipment
>> and possibly the aircraft avionics itself.
>
> Who said it was anything to do with interference to the systems on board
> the aircraft? Have you any clue what else it might be? Obviously not.

BTW, countless reasons including overloading base stations for great 
distances due to fantastic line of sight from the plane. Like to add a few 
yourself rather than just post an unhelpful missive.

Graham

The message <BNednV0FIL9NXvHVnZ2dnUVZ8vCdnZ2d@posted.metronet>
from "Graham"  contains these words:

> BTW, countless reasons including overloading base stations for great 
> distances due to fantastic line of sight from the plane. Like to add a few 
> yourself rather than just post an unhelpful missive.


You only have to look how the police helicopters and Helimeds operate. 
I am sure they quite easily set up a system on their main networks that
did not interfere with the avionics on board the aircraft.  But they
actually operate on channels exclusively used for airborne use which are
then linked to the main network.  

MB

"MB" <MB@invalid.invalid> wrote in message 
news:3130303030373135486CD59463@invalid.invalid...
> The message <BNednV0FIL9NXvHVnZ2dnUVZ8vCdnZ2d@posted.metronet>
> from "Graham"  contains these words:
>
>> BTW, countless reasons including overloading base stations for great
>> distances due to fantastic line of sight from the plane. Like to add a 
>> few
>> yourself rather than just post an unhelpful missive.
>
>
> You only have to look how the police helicopters and Helimeds operate.
> I am sure they quite easily set up a system on their main networks that
> did not interfere with the avionics on board the aircraft.  But they
> actually operate on channels exclusively used for airborne use which are
> then linked to the main network.

But, if there were two, three or many of those transmitters on board the 
aircraft, other sprurious frequencies would be produced locally that one 
transmitter alone would not create. When more than one transmitter is used 
close together they produce local mixing in any sensitive equipment that 
could well be outside the frequency coverage of a single transmitter. This 
is one very good reason to stop many mobiles being used at the same time in 
the back of aircraft.

Graham

"Graham"  wrote in message 
news:SJCdnctwrofLV_HVnZ2dnUVZ8u6dnZ2d@posted.metronet...
> But, if there were two, three or many of those transmitters on board the 
> aircraft, other sprurious frequencies would be produced locally that one 
> transmitter alone would not create. When more than one transmitter is used 
> close together they produce local mixing in any sensitive equipment that 
> could well be outside the frequency coverage of a single transmitter. This 
> is one very good reason to stop many mobiles being used at the same time 
> in the back of aircraft.

I think it's a bit worrying that aircraft are vulnerable to such things. 
After all, they move around a lot and must enounter many strong RF signals 
in all sorts of combinations. Until they sort these teething troubles out I 
think I'll stay on the ground.

Bill

"Bill Wright"  wrote in message 
news:jPKdnbiTDMf0TvHVnZ2dneKdnZydnZ2d@pipex.net...
>
> "Graham"  wrote in message 
> news:SJCdnctwrofLV_HVnZ2dnUVZ8u6dnZ2d@posted.metronet...
>> But, if there were two, three or many of those transmitters on board the 
>> aircraft, other sprurious frequencies would be produced locally that one 
>> transmitter alone would not create. When more than one transmitter is 
>> used close together they produce local mixing in any sensitive equipment 
>> that could well be outside the frequency coverage of a single 
>> transmitter. This is one very good reason to stop many mobiles being used 
>> at the same time in the back of aircraft.
>
> I think it's a bit worrying that aircraft are vulnerable to such things. 
> After all, they move around a lot and must enounter many strong RF signals 
> in all sorts of combinations. Until they sort these teething troubles out 
> I think I'll stay on the ground.
>

Remember, most of the equipment in a plane is fortunately inside a fairly 
good Faraday cage by the nature of its design (although leaky enough to 
perhaps allow phone comms with the ground). Its all a matter of degree. 
There may be enough signal in and out to contact a mobile base station, but 
not the vast amounts allowed through to actually risk RF interference. 
Banking around Crystal Palace is not going to have any effect on the 
internal equipment. Possible small chance of interference to comms, but this 
would be temporary as they passed overhead. However, mobile phones inside 
the plane, are free to get into anything on board and also much, much higher 
field strength than you could get from even passing the CP mast at 100ft, 
and that is assuming the plane was transparent to RF, but as I said, the 
opposite is true.
Graham

"Graham"  wrote in message 
news:a82dncrZQ_V3RvHVnZ2dnUVZ8tHinZ2d@posted.metronet...
>
> "Bill Wright"  wrote in message 
> news:jPKdnbiTDMf0TvHVnZ2dneKdnZydnZ2d@pipex.net...
>>
>> "Graham"  wrote in message 
>> news:SJCdnctwrofLV_HVnZ2dnUVZ8u6dnZ2d@posted.metronet...
>>> But, if there were two, three or many of those transmitters on board the 
>>> aircraft, other sprurious frequencies would be produced locally that one 
>>> transmitter alone would not create. When more than one transmitter is 
>>> used close together they produce local mixing in any sensitive equipment 
>>> that could well be outside the frequency coverage of a single 
>>> transmitter. This is one very good reason to stop many mobiles being 
>>> used at the same time in the back of aircraft.
>>
>> I think it's a bit worrying that aircraft are vulnerable to such things. 
>> After all, they move around a lot and must enounter many strong RF 
>> signals in all sorts of combinations. Until they sort these teething 
>> troubles out I think I'll stay on the ground.
>>
>
> Remember, most of the equipment in a plane is fortunately inside a fairly 
> good Faraday cage by the nature of its design (although leaky enough to 
> perhaps allow phone comms with the ground). Its all a matter of degree. 
> There may be enough signal in and out to contact a mobile base station, 
> but not the vast amounts allowed through to actually risk RF interference. 
> Banking around Crystal Palace is not going to have any effect on the 
> internal equipment. Possible small chance of interference to comms, but 
> this would be temporary as they passed overhead. However, mobile phones 
> inside the plane, are free to get into anything on board and also much, 
> much higher field strength than you could get from even passing the CP 
> mast at 100ft, and that is assuming the plane was transparent to RF, but 
> as I said, the opposite is true.
> Graham

Hmm, all this is mere theory in my opinion. I remember how they boasted 
about the Titanic!

Bill

Graham wrote:
> Banking around Crystal Palace is not going to have any effect on the 
> internal equipment. Possible small chance of interference to comms, but this 
> would be temporary as they passed overhead. However, mobile phones inside 
> the plane, are free to get into anything on board and also much, much higher 
> field strength than you could get from even passing the CP mast at 100ft, 
> and that is assuming the plane was transparent to RF, but as I said, the 
> opposite is true.

FM broadcast sites are designed to avoid overloading aircraft VHF
receivers. It's part of the service planning. Frequencies are chosen to
keep intermodulation products (generated in the VHF aircraft receiver's
front end) away from locally-used aviation frequencies, and the
broadcast antenna will have sufficient tiers to control the vertical
radiation pattern at high angles in order to protect aircraft. Ofcom's
rules specify the minimum number of antenna tiers as a function of ERP
for this reason.


-- 
Richard Lamont                        http://www.lamont.me.uk/

OpenPGP Key ID: 0xBD89BE41
Fingerprint: CE78 C285 1F97 0BDA 886D BA78 26D8 6C34 BD89 BE41

Graham wrote:

> There is good reason for using AM for aircraft communication, or rather good 
> reason not to use FM. If two aircraft transmit at the same time its very 
> obvious due to the hetrodyne and the controller knows instantly two aircraft 
> were trying to talk to him.
> 

Didn't stop Tenerife from happening in the 70s though did it!

Richard Lamont wrote:

> 
> FM broadcast sites are designed to avoid overloading aircraft VHF
> receivers. It's part of the service planning. Frequencies are chosen to
> keep intermodulation products (generated in the VHF aircraft receiver's
> front end) away from locally-used aviation frequencies, and the
> broadcast antenna will have sufficient tiers to control the vertical
> radiation pattern at high angles in order to protect aircraft. Ofcom's
> rules specify the minimum number of antenna tiers as a function of ERP
> for this reason.

I don't think any UK Band II broadcast station between 107.0 and 107.9 is 
allowed to be more than 1kW ERP, in fact most are about 100 watts ?

-- 
Mark
Please replace invalid and invalid with gmx and net to reply.

"funkmish" <funkmish@address.invalid> wrote in message 
news:g4iu31$a7u$1@south.jnrs.ja.net...
> Graham wrote:
>
>> There is good reason for using AM for aircraft communication, or 
>> rather good reason not to use FM. If two aircraft transmit at the 
>> same time its very obvious due to the hetrodyne and the controller 
>> knows instantly two aircraft were trying to talk to him.
>>
>
> Didn't stop Tenerife from happening in the 70s though did it!

But that wasn't a problem of radio communication as such [1], just a 
bloody minded senior pilot who decided that he had waited long enough 
and wanted to 'get home', IIRC it was even proved that he ignored his 
co-pilot protests as he brought the thrusts up on the engines.

[1] the main technical falling was the lack of ground radar.

"tony sayer"  wrote in message 
news:VmqWnlE9jJbIFwzp@bancom.co.uk...
> In article <GtWdnb3BqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet>, Graham
>  scribeth thus
>>
>>"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
>>news:6d2iomFfk6kU1@mid.individual.net...
>>> In news:g4h3cr$a3c$1@registered.motzarella.org,
>>> Graham.  typed, for some strange, unexplained reason:
>>>
>>> [snip]
>>>
>>> : Never mind digital, Civil Aviation has yet to be convinced that FM
>>> : has any merit over good old fashioned AM
>>>
>>> I suspect it's more a matter of cost. Imagine replacing every single
>>> transceiver in every single aircraft worldwide, plus all the base 
>>> station
>>> equipment.
>>>
>>> All at once.
>>>
>>> I do rather like AM for communications though, however getting equipment
>>> for it on the amateur bands is becoming more difficult these days, not
>>> many Pye Westminsters left ;-)
>>
>>There is good reason for using AM for aircraft communication, or rather 
>>good
>>reason not to use FM. If two aircraft transmit at the same time its very
>>obvious due to the hetrodyne and the controller knows instantly two 
>>aircraft
>>were trying to talk to him.
>>
>>Graham
>>
>>
>
> You do get that effect on FM but not quite the same way.
>
> As others might have said theres a lorra radios out there and they ain't
> cheap;!..

Yes, but only if the two carriers are of similar strengths.
Once one is a little stronger than the other only the stronger
one makes an impact. Capture effect.

-- 
Graham

%Profound_observation%

>
> Graham (nospamGraham, not privacy Graham :-)


Note the subtle change I have made to my sig :-)
-- 
Graham.

%Profound_observation%

"Paul Martin"  wrote in message 
news:slrng6o83l.6sq.pm@thinkpad.nowster.org.uk...
> In article <g4h3cr$a3c$1@registered.motzarella.org>,
> Graham. wrote:
>
>> Never mind digital, Civil Aviation has yet to be convinced that FM
>> has any merit over good old fashioned AM
>
> They use SSB on HF. It has the advantage that two stations can be
> calling at the same time on the same frequency, and they'll both be
> heard. They might not be understood, but they'll be heard as two calls.

This is not due to the fact that only one sideband is radiated, it is due
to the carrier being suppressed. The two things tend to go together
(but not always), so I may be accused of pedantry, but this is Usenet :-)

-- 
Graham.

%Profound_observation%

In article <g4j3se$a3b$1@registered.motzarella.org>, Graham.
 scribeth thus
>
>
>"tony sayer"  wrote in message 
>news:VmqWnlE9jJbIFwzp@bancom.co.uk...
>> In article <GtWdnb3BqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet>, Graham
>>  scribeth thus
>>>
>>>"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
>>>news:6d2iomFfk6kU1@mid.individual.net...
>>>> In news:g4h3cr$a3c$1@registered.motzarella.org,
>>>> Graham.  typed, for some strange, unexplained reason:
>>>>
>>>> [snip]
>>>>
>>>> : Never mind digital, Civil Aviation has yet to be convinced that FM
>>>> : has any merit over good old fashioned AM
>>>>
>>>> I suspect it's more a matter of cost. Imagine replacing every single
>>>> transceiver in every single aircraft worldwide, plus all the base 
>>>> station
>>>> equipment.
>>>>
>>>> All at once.
>>>>
>>>> I do rather like AM for communications though, however getting equipment
>>>> for it on the amateur bands is becoming more difficult these days, not
>>>> many Pye Westminsters left ;-)
>>>
>>>There is good reason for using AM for aircraft communication, or rather 
>>>good
>>>reason not to use FM. If two aircraft transmit at the same time its very
>>>obvious due to the hetrodyne and the controller knows instantly two 
>>>aircraft
>>>were trying to talk to him.
>>>
>>>Graham
>>>
>>>
>>
>> You do get that effect on FM but not quite the same way.
>>
>> As others might have said theres a lorra radios out there and they ain't
>> cheap;!..
>
>Yes, but only if the two carriers are of similar strengths.
>Once one is a little stronger than the other only the stronger
>one makes an impact. Capture effect.
>
Not as simple as that .. there is a heterodyne set up which gives the
indication that two carriers are present.....
-- 
Tony Sayer

In article <SJCdnctwrofLV_HVnZ2dnUVZ8u6dnZ2d@posted.metronet>, Graham
 scribeth thus
>
>"MB" <MB@invalid.invalid> wrote in message 
>news:3130303030373135486CD59463@invalid.invalid...
>> The message <BNednV0FIL9NXvHVnZ2dnUVZ8vCdnZ2d@posted.metronet>
>> from "Graham"  contains these words:
>>
>>> BTW, countless reasons including overloading base stations for great
>>> distances due to fantastic line of sight from the plane. Like to add a 
>>> few
>>> yourself rather than just post an unhelpful missive.
>>
>>
>> You only have to look how the police helicopters and Helimeds operate.
>> I am sure they quite easily set up a system on their main networks that
>> did not interfere with the avionics on board the aircraft.  But they
>> actually operate on channels exclusively used for airborne use which are
>> then linked to the main network.
>
>But, if there were two, three or many of those transmitters on board the 
>aircraft, other sprurious frequencies would be produced locally that one 
>transmitter alone would not create. When more than one transmitter is used 
>close together they produce local mixing in any sensitive equipment that 
>could well be outside the frequency coverage of a single transmitter. This 
>is one very good reason to stop many mobiles being used at the same time in 
>the back of aircraft.
>
>Graham
>
>

Have you ever given this any series thought as to how "in flight
telephony" will be effected?..
-- 
Tony Sayer

In article <LoydnaEAHLmIJ_HVnZ2dnUVZ8vydnZ2d@posted.metronet>, Graham
 scribeth thus
>
>"tony sayer"  wrote in message 
>news:zEA$PrFXWLbIFw0z@bancom.co.uk...
>> In article <dKidnXEgw8iFNPHVRVnytQA@posted.metronet>, Graham
>>  scribeth thus
>>>
>>>"tony sayer"  wrote in message
>>>news:WGdWfwEjlJbIFwwA@bancom.co.uk...
>>>> In article <3130303030373135486C23B048@invalid.invalid>, MB
>>>> <MB@invalid.invalid> scribeth thus
>>>>>The message <g4h3cr$a3c$1@registered.motzarella.org>
>>>>>from "Graham."  contains these words:
>>>>>
>>>>>> >
>>>>>> > Yep, that is precisely what I would expect with the conditions I 
>>>>>> > heard
>>>>>> > this morning. I'll miss all this when the dreaded day comes and they
>>>>>> > switch off Band II radio. I really think its such a backward step
>>>>>> > going to
>>>>>> > digital when we have such an excellent analogue radio system in 
>>>>>> > place.
>>>>>> > Perhaps a dual system but not do away with our well tried and tested
>>>>>> > VHF
>>>>>> > FM system. This rush to digital is so narrow minded. When I see the
>>>>>> > day
>>>>>> > they change air traffic control communications to digital, then
>>>>>> > perhaps
>>>>>> > I'll concede the technology has matured enough, but I still won't be
>>>>>> > going
>>>>>> > on any planes around that time.
>>>>>
>>>>>> Never mind digital, Civil Aviation has yet to be convinced that FM
>>>>>> has any merit over good old fashioned AM
>>>>>
>>>>>
>>>>>
>>>>>Main ATC channels might still be VHF AM but quite a lot of information
>>>>>is passed between air <> ground <> air using various data systems.  Many
>>>>>airports are going to TETRA for their ground services.  There are
>>>>>arguments about why they prefer to stay on AM (apart from inertia) which
>>>>>I can't remember in detail but it is not a simple case of AM = bad, FM -
>>>>>good.
>>>>>
>>>>>The RAF and RN still use HF for their SAR helicopters but the Coastguard
>>>>>use satellite comms (i.e. digital) with no HF on board.  if they want to
>>>>>speak to Kinloss ARCC they just call them up on the phone.
>>>>>
>>>>>I heard one plane trying to call Prestwick and unable to get them so he
>>>>>had a message relayed through a passing Speedbird, Prestwick passed
>>>>>their phone number so he could just call them on his mobile next time he
>>>>>has problems.  So indirectly digital is creeping into ATC!
>>>>>
>>>>>MB
>>>>
>>>> Umm .... using mobiles in aircraft to contact ground based stations
>>>> isn't a very clever idea!..
>>>
>>>I think there is a big difference to a pilot using a mobile compared to a
>>>bunch of tossers in the back yakking away on them randomly. For a start 
>>>the
>>>pilot would instantly know if something went wrong or indicated 
>>>incorrectly
>>>the moment he used the phone. Using it for getting info from the ground,
>>>compared to not having that info, its obviously a good move. The actual
>>>chances of a mobile interfering is very slight, but of course that does 
>>>not
>>>mean we want yakkers in the back to start using lots of them at the same
>>>time. The mixing of signals and spurious signals created due to them all
>>>going at once would indeed make a risk of interference to radio equipment
>>>and possibly the aircraft avionics itself.
>>>
>>>Graham
>>>
>>>
>> Its nothing to do with tossers yakking and all that, its more about
>> frequency reuse among base stations on the ground. It wasn't planned to
>> have mobile units at umpteen thousand feet ....
>
>Thats one reason, but the fact remains that intermodulation frequencies from 
>many phones transmitting at once and within feet of each other is a big 
>problem to the aircraft operation as the mixing products will also be very 
>strong. 

And where will that happen?..

>Anyone with knowledge of RF knows how nasty that mixing will be in 
>the front end of a receiver, not to mention the general field strength of 
>any one phone, that could get into wiring and avionics.

The harmonics and noise will get in precisely where?..


>
>Graham (nospamGraham, not privacy Graham :-) 
>
>

-- 
Tony Sayer

In article , Bill Wright
 scribeth thus
>
>"Graham"  wrote in message 
>news:SJCdnctwrofLV_HVnZ2dnUVZ8u6dnZ2d@posted.metronet...
>> But, if there were two, three or many of those transmitters on board the 
>> aircraft, other sprurious frequencies would be produced locally that one 
>> transmitter alone would not create. When more than one transmitter is used 
>> close together they produce local mixing in any sensitive equipment that 
>> could well be outside the frequency coverage of a single transmitter. This 
>> is one very good reason to stop many mobiles being used at the same time 
>> in the back of aircraft.
>
>I think it's a bit worrying that aircraft are vulnerable to such things. 
>After all, they move around a lot and must enounter many strong RF signals 
>in all sorts of combinations. Until they sort these teething troubles out I 
>think I'll stay on the ground.
>
>Bill 
>
>

Yes good idea M8!...

One of the safest ways of travelling there is. Just how many aircraft
movements a day do Easyjet and Ryanair make let alone the other
carriers!...
-- 
Tony Sayer

In article <486cf644$0$78073$5a6aecb4@news.aaisp.net.uk>, Richard Lamont
 scribeth thus
>Graham wrote:
>> Banking around Crystal Palace is not going to have any effect on the 
>> internal equipment. Possible small chance of interference to comms, but this 
>> would be temporary as they passed overhead. However, mobile phones inside 
>> the plane, are free to get into anything on board and also much, much higher 
>> field strength than you could get from even passing the CP mast at 100ft, 
>> and that is assuming the plane was transparent to RF, but as I said, the 
>> opposite is true.
>
>FM broadcast sites are designed to avoid overloading aircraft VHF
>receivers. It's part of the service planning. Frequencies are chosen to
>keep intermodulation products (generated in the VHF aircraft receiver's
>front end) away from locally-used aviation frequencies, and the
>broadcast antenna will have sufficient tiers to control the vertical
>radiation pattern at high angles in order to protect aircraft. Ofcom's
>rules specify the minimum number of antenna tiers as a function of ERP
>for this reason.
>
>

And the filtering ... very stringent....
-- 
Tony Sayer

In article , Mark Carver
<mark.carver@invalid.invalid> scribeth thus
>Richard Lamont wrote:
>
>> 
>> FM broadcast sites are designed to avoid overloading aircraft VHF
>> receivers. It's part of the service planning. Frequencies are chosen to
>> keep intermodulation products (generated in the VHF aircraft receiver's
>> front end) away from locally-used aviation frequencies, and the
>> broadcast antenna will have sufficient tiers to control the vertical
>> radiation pattern at high angles in order to protect aircraft. Ofcom's
>> rules specify the minimum number of antenna tiers as a function of ERP
>> for this reason.
>
>I don't think any UK Band II broadcast station between 107.0 and 107.9 is 
>allowed to be more than 1kW ERP, in fact most are about 100 watts ?
>

There are the odd 10 kW plus arrangements permitted in other countries..
-- 
Tony Sayer

"tony sayer"  wrote in message 
news:AvwDFHBUuRbIFwRC@bancom.co.uk...
> In article <486cf644$0$78073$5a6aecb4@news.aaisp.net.uk>, Richard Lamont
> And the filtering ... very stringent....

Like the judging exams then? Or were they 'rigorous'?

Bill

"tony sayer"  wrote in message 
news:cPzE97AatRbIFwwv@bancom.co.uk...
> In article , Bill Wright
> One of the safest ways of travelling there is. Just how many aircraft
> movements a day do Easyjet and Ryanair make let alone the other
> carriers!...

Yes but what if it runs out of petrol? There's no hard shoulder up there is 
there?

Bill

Mark Carver wrote:
> Richard Lamont wrote:
> 
>>
>> FM broadcast sites are designed to avoid overloading aircraft VHF
>> receivers. It's part of the service planning. Frequencies are chosen to
>> keep intermodulation products (generated in the VHF aircraft receiver's
>> front end) away from locally-used aviation frequencies, and the
>> broadcast antenna will have sufficient tiers to control the vertical
>> radiation pattern at high angles in order to protect aircraft. Ofcom's
>> rules specify the minimum number of antenna tiers as a function of ERP
>> for this reason.
> 
> I don't think any UK Band II broadcast station between 107.0 and 107.9
> is allowed to be more than 1kW ERP, in fact most are about 100 watts ?

I think that is because the Radio Authority started to develop the
105-108 MHz sub-band by putting regional stations in 105-106 and
'sallies' in 107-108. Maybe they decided to put the low power stuff at
the top end because of the aviation thing.


-- 
Richard Lamont                        http://www.lamont.me.uk/

OpenPGP Key ID: 0xBD89BE41
Fingerprint: CE78 C285 1F97 0BDA 886D BA78 26D8 6C34 BD89 BE41

On Thu, 3 Jul 2008 17:42:14 +0100, Jerry <INVALID@INVALID.INVALID> wrote:

> But that wasn't a problem of radio communication as such [1], just a 
> bloody minded senior pilot who decided that he had waited long enough 
> and wanted to 'get home', IIRC it was even proved that he ignored his 
> co-pilot protests as he brought the thrusts up on the engines.

The flight engineer I believe, who actually cut the power on the first
attempt the pilot made to leave.

Graham. wrote:
> "Paul Martin"  wrote in message 
> news:slrng6o83l.6sq.pm@thinkpad.nowster.org.uk...
>> In article <g4h3cr$a3c$1@registered.motzarella.org>,
>> Graham. wrote:
>>
>>> Never mind digital, Civil Aviation has yet to be convinced that FM
>>> has any merit over good old fashioned AM
>> They use SSB on HF. It has the advantage that two stations can be
>> calling at the same time on the same frequency, and they'll both be
>> heard. They might not be understood, but they'll be heard as two calls.
> 
> This is not due to the fact that only one sideband is radiated, it is due
> to the carrier being suppressed. The two things tend to go together
> (but not always), so I may be accused of pedantry, but this is Usenet :-)
> 
*AM* has the advantage...

I vaguely remember an incident where the recordings showed two pilots 
responding simultaneously to ATC.  One wasn't heard, but was there in 
the background.  With FM the weaker signal will be lost completely; 
with AM there's a chance the weaker one will be heard in the background.

But they even use AM for datalink (ACARS) although I think the new stuff 
is going to D8PSK which *is* a modern modulation.

Andy

"tony sayer"  wrote in message 
news:VPrG9JA6oRbIFwRl@bancom.co.uk...
> In article <g4j3se$a3b$1@registered.motzarella.org>, Graham.
>  scribeth thus
>>
>>
>>"tony sayer"  wrote in message
>>news:VmqWnlE9jJbIFwzp@bancom.co.uk...
>>> In article <GtWdnb3BqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet>, Graham
>>>  scribeth thus
>>>>
>>>>"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
>>>>news:6d2iomFfk6kU1@mid.individual.net...
>>>>> In news:g4h3cr$a3c$1@registered.motzarella.org,
>>>>> Graham.  typed, for some strange, unexplained reason:
>>>>>
>>>>> [snip]
>>>>>
>>>>> : Never mind digital, Civil Aviation has yet to be convinced that FM
>>>>> : has any merit over good old fashioned AM
>>>>>
>>>>> I suspect it's more a matter of cost. Imagine replacing every single
>>>>> transceiver in every single aircraft worldwide, plus all the base
>>>>> station
>>>>> equipment.
>>>>>
>>>>> All at once.
>>>>>
>>>>> I do rather like AM for communications though, however getting 
>>>>> equipment
>>>>> for it on the amateur bands is becoming more difficult these days, not
>>>>> many Pye Westminsters left ;-)
>>>>
>>>>There is good reason for using AM for aircraft communication, or rather
>>>>good
>>>>reason not to use FM. If two aircraft transmit at the same time its very
>>>>obvious due to the hetrodyne and the controller knows instantly two
>>>>aircraft
>>>>were trying to talk to him.
>>>>
>>>>Graham
>>>>
>>>>
>>>
>>> You do get that effect on FM but not quite the same way.
>>>
>>> As others might have said theres a lorra radios out there and they ain't
>>> cheap;!..
>>
>>Yes, but only if the two carriers are of similar strengths.
>>Once one is a little stronger than the other only the stronger
>>one makes an impact. Capture effect.
>>
> Not as simple as that .. there is a heterodyne set up which gives the
> indication that two carriers are present.....


If the two carriers differ in frequency. But isn't the whole point
of a well designed FM discriminator to eliminate the amplitude
components such as heterodyning and signal fading?
-- 
Graham.

%Profound_observation%

"tony sayer"  wrote in message 
news:ffNEZsAjrRbIFwwp@bancom.co.uk...
> In article <SJCdnctwrofLV_HVnZ2dnUVZ8u6dnZ2d@posted.metronet>, Graham
>  scribeth thus
>>
>>"MB" <MB@invalid.invalid> wrote in message
>>news:3130303030373135486CD59463@invalid.invalid...
>>> The message <BNednV0FIL9NXvHVnZ2dnUVZ8vCdnZ2d@posted.metronet>
>>> from "Graham"  contains these words:
>>>
>>>> BTW, countless reasons including overloading base stations for great
>>>> distances due to fantastic line of sight from the plane. Like to add a
>>>> few
>>>> yourself rather than just post an unhelpful missive.
>>>
>>>
>>> You only have to look how the police helicopters and Helimeds operate.
>>> I am sure they quite easily set up a system on their main networks that
>>> did not interfere with the avionics on board the aircraft.  But they
>>> actually operate on channels exclusively used for airborne use which are
>>> then linked to the main network.
>>
>>But, if there were two, three or many of those transmitters on board the
>>aircraft, other sprurious frequencies would be produced locally that one
>>transmitter alone would not create. When more than one transmitter is used
>>close together they produce local mixing in any sensitive equipment that
>>could well be outside the frequency coverage of a single transmitter. This
>>is one very good reason to stop many mobiles being used at the same time 
>>in
>>the back of aircraft.
>>
>>Graham
>>
>>
>
> Have you ever given this any series thought as to how "in flight
> telephony" will be effected?..


You meant serious, not sure if you meant effected or affected.
If the former, and you are talking about the passengers being able
to use their GSM handsets, then the on board cell will ensure
the handsets use very little TX power
-- 
Graham.

%Profound_observation%

In news:g4jk7p$3va$1@registered.motzarella.org,
Graham.  typed, for some strange, unexplained reason:

[snip]

: If the two carriers differ in frequency. But isn't the whole point
: of a well designed FM discriminator to eliminate the amplitude
: components such as heterodyning and signal fading?

Exactly why AM is preferred on ATC..!


Ivor

In article <g4jk7p$3va$1@registered.motzarella.org>, Graham.
 scribeth thus
>
>
>"tony sayer"  wrote in message 
>news:VPrG9JA6oRbIFwRl@bancom.co.uk...
>> In article <g4j3se$a3b$1@registered.motzarella.org>, Graham.
>>  scribeth thus
>>>
>>>
>>>"tony sayer"  wrote in message
>>>news:VmqWnlE9jJbIFwzp@bancom.co.uk...
>>>> In article <GtWdnb3BqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet>, Graham
>>>>  scribeth thus
>>>>>
>>>>>"Ivor Jones" <ivor@thisaddressis.invalid> wrote in message
>>>>>news:6d2iomFfk6kU1@mid.individual.net...
>>>>>> In news:g4h3cr$a3c$1@registered.motzarella.org,
>>>>>> Graham.  typed, for some strange, unexplained reason:
>>>>>>
>>>>>> [snip]
>>>>>>
>>>>>> : Never mind digital, Civil Aviation has yet to be convinced that FM
>>>>>> : has any merit over good old fashioned AM
>>>>>>
>>>>>> I suspect it's more a matter of cost. Imagine replacing every single
>>>>>> transceiver in every single aircraft worldwide, plus all the base
>>>>>> station
>>>>>> equipment.
>>>>>>
>>>>>> All at once.
>>>>>>
>>>>>> I do rather like AM for communications though, however getting 
>>>>>> equipment
>>>>>> for it on the amateur bands is becoming more difficult these days, not
>>>>>> many Pye Westminsters left ;-)
>>>>>
>>>>>There is good reason for using AM for aircraft communication, or rather
>>>>>good
>>>>>reason not to use FM. If two aircraft transmit at the same time its very
>>>>>obvious due to the hetrodyne and the controller knows instantly two
>>>>>aircraft
>>>>>were trying to talk to him.
>>>>>
>>>>>Graham
>>>>>
>>>>>
>>>>
>>>> You do get that effect on FM but not quite the same way.
>>>>
>>>> As others might have said theres a lorra radios out there and they ain't
>>>> cheap;!..
>>>
>>>Yes, but only if the two carriers are of similar strengths.
>>>Once one is a little stronger than the other only the stronger
>>>one makes an impact. Capture effect.
>>>
>> Not as simple as that .. there is a heterodyne set up which gives the
>> indication that two carriers are present.....
>
>
>If the two carriers differ in frequency. But isn't the whole point
>of a well designed FM discriminator to eliminate the amplitude
>components such as heterodyning and signal fading?


As may be but after some 30 odd years listening to FM comms systems you
can always tell when more then the one carrier is up. However this is a
rather strawman argument the real argument is the cost of converting ALL
aircraft to a different system!. After all the existing one works rather
well don't you think?..
-- 
Tony Sayer

In article , Ivor Jones
<ivor@thisaddressis.invalid> scribeth thus
>In news:g4jk7p$3va$1@registered.motzarella.org,
>Graham.  typed, for some strange, unexplained reason:
>
>[snip]
>
>: If the two carriers differ in frequency. But isn't the whole point
>: of a well designed FM discriminator to eliminate the amplitude
>: components such as heterodyning and signal fading?
>
>Exactly why AM is preferred on ATC..!
>

AM does do this quite well but it still happens on FM systems. As stated
elsewhere there are a lot of Radios out there to convert to any other
system, and in the main AM does do its job very well for what's
required..
>
>Ivor
>

-- 
Tony Sayer

In article , Bill Wright
 scribeth thus
>
>"tony sayer"  wrote in message 
>news:cPzE97AatRbIFwwv@bancom.co.uk...
>> In article , Bill Wright
>> One of the safest ways of travelling there is. Just how many aircraft
>> movements a day do Easyjet and Ryanair make let alone the other
>> carriers!...
>
>Yes but what if it runs out of petrol? There's no hard shoulder up there is 
>there?
>
>Bill 
>
>

Wouldn't be a wanting anything too hard;)..
-- 
Tony Sayer

In article <g4jk7p$3va$2@registered.motzarella.org>, Graham.
 scribeth thus
>
>
>"tony sayer"  wrote in message 
>news:ffNEZsAjrRbIFwwp@bancom.co.uk...
>> In article <SJCdnctwrofLV_HVnZ2dnUVZ8u6dnZ2d@posted.metronet>, Graham
>>  scribeth thus
>>>
>>>"MB" <MB@invalid.invalid> wrote in message
>>>news:3130303030373135486CD59463@invalid.invalid...
>>>> The message <BNednV0FIL9NXvHVnZ2dnUVZ8vCdnZ2d@posted.metronet>
>>>> from "Graham"  contains these words:
>>>>
>>>>> BTW, countless reasons including overloading base stations for great
>>>>> distances due to fantastic line of sight from the plane. Like to add a
>>>>> few
>>>>> yourself rather than just post an unhelpful missive.
>>>>
>>>>
>>>> You only have to look how the police helicopters and Helimeds operate.
>>>> I am sure they quite easily set up a system on their main networks that
>>>> did not interfere with the avionics on board the aircraft.  But they
>>>> actually operate on channels exclusively used for airborne use which are
>>>> then linked to the main network.
>>>
>>>But, if there were two, three or many of those transmitters on board the
>>>aircraft, other sprurious frequencies would be produced locally that one
>>>transmitter alone would not create. When more than one transmitter is used
>>>close together they produce local mixing in any sensitive equipment that
>>>could well be outside the frequency coverage of a single transmitter. This
>>>is one very good reason to stop many mobiles being used at the same time 
>>>in
>>>the back of aircraft.
>>>
>>>Graham
>>>
>>>
>>
>> Have you ever given this any series thought as to how "in flight
>> telephony" will be effected?..
>
>
>You meant serious, not sure if you meant effected or affected.

Effected i.e. -how- they will do it;)..

>If the former, and you are talking about the passengers being able
>to use their GSM handsets, then the on board cell will ensure
>the handsets use very little TX power

Thats the point .. very little power their not going to be able to
contact ground stations directly so no danger of full GSM spec power
being used. 

I rather reckon there will be a modification to the existing spec for a
Aircraft capable mobile rather like there are dual and Quad band system
units  etc..

Perish the bloody thought to. All that Yakking in a confined spec. I
hate airliner flying simply because of the confining situation for more
than a couple of hours. Train travel .. well at least you can wander
around;)..
-- 
Tony Sayer

On 3 Jul,  
     Richard Lamont  wrote:

> FM broadcast sites are designed to avoid overloading aircraft VHF
> receivers. It's part of the service planning. Frequencies are chosen to
> keep intermodulation products (generated in the VHF aircraft receiver's
> front end) away from locally-used aviation frequencies, and the
> broadcast antenna will have sufficient tiers to control the vertical
> radiation pattern at high angles in order to protect aircraft. Ofcom's
> rules specify the minimum number of antenna tiers as a function of ERP
> for this reason.

There were problems with a police helicopter conducting a search in the
vicinity of an HP VHF site several years ago. Transmitted ERP had to be
reduced considerably so that the full functionality of the search equipment
could be used. Safety of the aircraft was not affected.
 
-- 
  BD
  Change lycos to yahoo to reply

> There were problems with a police helicopter conducting a search in the
> vicinity of an HP VHF site several years ago. Transmitted ERP had to be
> reduced considerably so that the full functionality of the search 
> equipment
> could be used.

Is that the way it was reported? Not very enlightening.  I wonder what was
being affected.
-- 
Graham.

%Profound_observation%

tony sayer wrote:

> Perish the bloody thought to. All that Yakking in a confined spec. I
> hate airliner flying simply because of the confining situation for more
> than a couple of hours. Train travel .. well at least you can wander
> around;)..

True, but tricky and often time consuming to get to islands and/or far off 
lands using the train  ;-)

I agree with you about the use of mobiles on board a plane. Bad idea IMHO.

Perhaps they should just transmit a sterile GSM carrier. Then the phones would 
be forced into low power mode, but with no ability to make or receive calls.

-- 
Mark
Please replace invalid and invalid with gmx and net to reply.

The message <g4i1l4$bck$1@registered.motzarella.org>
from "Jerry" <INVALID@INVALID.INVALID> contains these words:


> "Graham"  wrote in message 
> news:GtWdnYLBqdAO6PHVnZ2dnUVZ8svinZ2d@posted.metronet...
> >
> > "Graham."  wrote in message 
> > news:g4h3cr$a3c$1@registered.motzarella.org...
> >>
> >> "Graham"  wrote in message 
> >> news:nMGdnTZy4JV8V_bVnZ2dnUVZ8hidnZ2d@posted.metronet...
> >>>

> God, following who said what in this thread is becoming confusing..... 

...as is trying to find any reference to the original topic after
posting No. 7 (out of 58 currently)

Mike