Hanninton Multiplex; Reception of Digital Radio Channels (DAB)`

In article ,
Grappler wrote:
On Fri, 11 Aug 2006 21:06:28 GMT, Marky P
wrote:

I wanted to set up a pirate station once. I was all ready to jump in
& buy a transmitter 'till someone told me that I lived on the doorstep
of the blokes who monitor dodgy radio stuff (Baldock, Herts) & I would
be switched off & locked up in seconds :-(.

Marky P.

I used to work for the G.P.O. (telephones) back in the sixties and I
had great fun running 10 watts on medium wave.

It stopped all of a sudden when I heard someone in the same building
saying that he was on overtime that night to catch a local pirate....

so it wasn't you whose home made transmitter was wired up with GPO jumper
wire?

--
From KT24 - in drought-ridden Surrey

Using a RISC OS5 computer

In article , Grappler
writes
On Fri, 11 Aug 2006 21:06:28 GMT, Marky P
wrote:

I wanted to set up a pirate station once. I was all ready to jump in
& buy a transmitter 'till someone told me that I lived on the doorstep
of the blokes who monitor dodgy radio stuff (Baldock, Herts) & I would
be switched off & locked up in seconds :-(.

Marky P.

I used to work for the G.P.O. (telephones) back in the sixties and I
had great fun running 10 watts on medium wave.

It stopped all of a sudden when I heard someone in the same building
saying that he was on overtime that night to catch a local pirate....

Oh those men in green vans...






Many years ago now there used to be a medium wave pirate in the badlands of
the fens on 207 meters on the medium raveband etc.

Well one day said pirate used to Broadcast from a council estate in the
village of Fordham near Newmarket Suffolke. Seems that one afternoon the
local GPO bloke turned up called Mr John Nolan Thomas, yep that was his real
name!

Seemed that he came down the road not in a green van but a MK2 ford Cortina
waving a transistor wireless out of the window. Car duly stopped pirate in
charge of transmitter, 4 x 807's nailed to a plank of wood, removed crystal at
the same time as Mr Thomas went down the footpath round to the back of the
houses and disappeared from view. Said pirate artfully nipped into his car
which was left unlocked and wipped the bonnet up and reversed Two of the
ignition leads, replaced the bonnet and legged it off down the pub for Sunday
lunchtime drinkies.

Came back after a few, to see the spectacle of Mr Thomas with an AA man,
bonnet up of Cortina and a lot of head scratching going on. Very dirty looks
from Mr Thomas to said pirate operative, who commented that the firing order
was noted as going askew on said Cortina's, and the leads did "very odd
things" with a knowing wink to Mr AA. Around 10 mins later cortina drove off
with more grim looks from Mr Thomas..

Happy innocent pirate days, unlike youth of today etc!.....
--
Tony Sayer

In article , Marky P
writes
On Fri, 11 Aug 2006 19:14:45 +0100, "Bill Wright"
wrote:


"charles" wrote in message
.. .
In article ,
Bill Wright wrote:

"Mark Carver" wrote in message


[Snip]

So I just got fed up of using two aerials, two attenuators, two bandpass
filters and a combiner, when one aerial one bandpass filter and one
attenuator worked just as well.

What about unwanted 'out of band' signals when you do it that way? From
un-attended police stations, for instance.

It's certainly necessary to have a good look at the territory around 150MHz.
In a city I would try to leave the analyser on 'store' for an hour, although
that is no protection against the ham with a 200W 2m rig in his car.

In practice I would only use the 'one aerial' technique in areas of very
high FM and DAB field strength, so there will be a 12dB or 18dB attenuator
in the aerial feeder, which gives a lot of protection against transmissions
from the nearby streets. After all, the system should be able to stand a
narrowband signal 15dB above the broadcast signals without any problem.

On systems where there are very long cable runs it's essential to attenuate
the lower frequencies at each repeater (equalisation or 'slope') --
otherwise the repeaters can get very bad indigestion if the local ham cranks
up his burner!

Did you see that thing I wrote for 'Television' a few years ago about the
problems caused by local FM transmitters (pirates and RSLs)?

Bill

I wanted to set up a pirate station once. I was all ready to jump in
& buy a transmitter 'till someone told me that I lived on the doorstep
of the blokes who monitor dodgy radio stuff (Baldock, Herts) & I would
be switched off & locked up in seconds :-(.

Marky P.


Used to take 'em a bit longer then that, so I'm told
--
Tony Sayer

Gel wrote:

Thanks all for your useful posts.

Glad I checked before I started adjusting my coax cable set up.

(Just North West of Newbury).



I'm in Wash Common, in a slightly unfortunate position for Hannington,
as the hill I live on is between Hannington and me.

But having said that, my FM aerial picks up a solid signal and although
I originally intended to fit a DAB aerial, I can't see why I need to
bother, so I haven't and probably never will.

But having said that, my FM aerial picks up a solid signal and although
I originally intended to fit a DAB aerial, I can't see why I need to
bother, so I haven't and probably never will.

Jim Lesurf wrote:
In article .com,

The above indicates that - even at the relatively low ERPs used for
DAB, you may find that almost anything will work as an antenna for
reliable DAB reception. Very different behaviour to FM.


It's unlucky that you have poor FM reception, because I've lived in several
locations around the UK in the past decade and I've had very good FM
reception in each of these locations. Perhaps the problem is that you live
out in the sticks?

What FM tuner are you using? If it's an old one, have you considered buying
a new one? And what FM aerial are you using?

BTW, it speaks volumes that you write a long post saying how good DAB is
without even the slightest mention of the audio quality being crap.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/fr..._receivers.php
http://www.digitalradiotech.co.uk/dab/dab_radios.php

Jim Lesurf wrote:

I have been impressed by just how reliable DAB reception can be even
for signal levels far below those needed for decent FM reception.


There's a difference in required C/N of about 30 dB. Have you not taken that
into consideration?


It
also seems to me to be significantly more resistant to impulse
interference. It confirms the ideas behind the orginal development of
DAB to provide very reliable and robust data linkage and overcome the
practical problems of FM.


Although I'm not disputing that one of the main aims of designing DAB was to
provide reliable reception quality, this is the first paragraph of the DAB
spec proper:

"1 Scope

This European Telecommunication Standard (ETS) establishes a broadcasting
standard for the Digital Audio Broadcasting (DAB) system designed for
delivery of ****high-quality digital audio programme**** and data services
for mobile, portable and fixed reception from terrestrial or satellite
transmitters in the Very High Frequency (VHF)/Ultra High Frequency (UHF)
frequency bands as well as for distribution through cable networks. The DAB
system is designed to provide spectrum and power efficient techniques in
terrestrial transmitter network planning, known as the Single Frequency
Network (SFN) and the gap-filling technique. The DAB system is suitable for
satellite as well as hybrid/mixed terrestrial/satellite broadcasting, using
a simple, nearly omni-directional receiving antenna. The DAB system meets
the required sharing criteria with other radiocommunication services."

So don't try and suggest that DAB was designed to provide reliable reception
and it wasn't designed to provide high audio quality, which is really what
you're implying.


Quite a nice demo of the effectiveness of
the comms techniques employed.


Jim, if you think the digital comms techniques employed on DAB are good then
you really haven't got the first clue about digital comms. Sorry.

DAB's FEC coding is almost as weak as you can possibly get. Just like with
the audio codec, they went for minimum computational complexity and accepted
the resulting very poor spectral efficiency. But their decision to use a
highly inefficient audio codec and weak FEC coding is the reason Radio 3 is
now transmitting at the audio quality it is transmitting at.

So, is it really that effective when the audio quality across the board is
so ****? I think not.

Here's a figure of the unequal protection code rates applied to the MP2
audio frame on DAB:

http://www.digitalradiotech.co.uk/im...fec_coding.gif

DAB's FEC coding has a single layer, so there's bugger all else to catch any
bit errors, unlike almost all of the modern digital broadcasting systems,
which use at least 2 layers of FEC coding (you don't need to use 2 layers,
but if you don't you have to make sure that the single layer is strong as
fk, which DAB's is not).

The big problem seems to be with the protection of the scale factors.
Something as crucial to correct audio playback as the scale factors are need
stronger protection than a 1/2 code rate convolutional code rate.

Then again, radio reception is all relative: if your signal strength is
above the required threshold and you don't have any reception problems then
you could easily come to incorrect conclusions such as the one you came to.

Basically, radio reception is all relative, and if you don't suffer from
reception problems then all that really means is that your signal strength
is above the threshold required -- your comment is basically a gross
generalisation, and it is effectively saying "digital communication systems
can work correctly". Well, hold the bleeding back page...


This makes it all the more frustrating that I am now in the process of
perparing to install UHF distribution around the house - mainly to get
sound radio via 'Freeview' and (I hope!) bypass both our local FM
reception condition problems and the 'quart in a pint pot' of BBC
DAB.


Ooooh, he's deigned to say it.


The DAB RF signal and tuner are fine...


The DAB system is not fine, though, and it is the design of the DAB system
that CAUSES the audio quality to be as bad as it is.

Are you aware that the DAB system is about to be updated to replace the MP2
audio codec and hugely strengthen the FEC coding? Well it is. If it was as
good as you seem to be suggesting then there would be no need to update it.


shame about the BBC's
attitude to the content. :-/


Their attitude towards audio quality has been this way since 18th December
2001. How come you've just recognised this problem? Was it perhaps that your
beloved Radio 3 wasn't so badly affected but now it is?



--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/fr..._receivers.php
http://www.digitalradiotech.co.uk/dab/dab_radios.php

charles wrote:
In article ,
DAB sounds worse than FM wrote:
Jim Lesurf wrote:
In article .com,

The above indicates that - even at the relatively low ERPs used for
DAB, you may find that almost anything will work as an antenna for
reliable DAB reception. Very different behaviour to FM.


It's unlucky that you have poor FM reception, because I've lived in
several locations around the UK in the past decade and I've had very
good FM reception in each of these locations. Perhaps the problem is
that you live out in the sticks?

I could take you to plenty of places within a 30 mile radius of
Trafalgar Square where FM reception isn't easy. I certainly rejected
bying a house only 2 miles from here becasue of impossible FM
reception.


I get crap DAB reception on one of the 4 multiplexes I can receive despite
the transmitter for it being only 5 miles away. Does that mean that DAB
reception should be described as being "difficult"?




--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/fr..._receivers.php
http://www.digitalradiotech.co.uk/dab/dab_radios.php

In article , charles
wrote:


Yes, new tuners seem to be better at AM rejection (multipath) and often
have a narrower IF bandwidth (avoiding birdies) , but tend to be less
sensitive.

FWIW I use three different FM tuners, fed from different antennas.
Nominally, the 'best' tuner is a Yamaha CT7000. When it was first produced
and sold this was an outstandingly good FM tuner, compared with its
contemporaries. Even nowdays it has a good reputation. However it is now
quite old, and it is over a decade since I last checked the alignment, etc.
It is also prone to poor internal connections, and has a poorer effective
NF than some other tuners. I've more than once had to open it up and clean
or remake some of the internal connections. However I suspect that part of
the problem now may be poor internal connections that are not entirely
ohmic.

Hence I may well decide to try using a newer FM tuner at some point. Alas,
as I indicated, I get various types of interference here, and this shows on
all the FM tuners I use.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"DAB sounds worse than FM" wrote in message
...
Jim Lesurf wrote:
In article .com,

The above indicates that - even at the relatively low ERPs used for
DAB, you may find that almost anything will work as an antenna for
reliable DAB reception. Very different behaviour to FM.


It's unlucky that you have poor FM reception, because I've lived in
several
locations around the UK in the past decade and I've had very good FM
reception in each of these locations. Perhaps the problem is that you live
out in the sticks?
It's very unusual to find somewhere where the BBC DAB mux outperforms BBC FM
in terms of signal strength. However, in rural valleys and urban canyons,
where multipath is severe, DAB can emerge the clear winner.

As I write this the fool on Classic FM just gabbled "DAB digital radio on
100 to 102 FM!"

Bill