Jungle Sunrise wrote
"
What I meant to write was that all FM transmissions are NOT digital. I
could not send a rejoinder to rectify what I wrote because I had used up all
my allowable postings.

"

The contents of your posting conveys otherwise which leads me to suspect you
have a misconception of what digital Radio is.  Being one of the best ( or
rather the best) Engineer in the Gambia makes one wonder what your
credentials are if you cannot even answer a simple question within your
career domain.  Woe betide the gambian if all her Engineers are your like.



Mr Njie,

Yus was right when he said

"
>one has to have a digital radio to receive >transmissions
>from a digital radio station.  "

I think your impression of digital transmission is the opposite to what it
is.  It is more expensive and limited in distance ( but this can be overcome
by strategically placed transmitters or by satellite.  Digital signals are
also susceptible to distortion and noise
which, is usually minimized by building into receivers a centre-sampler
circuitry for determining the threshold value for received signals ( i.e
anything above the threshold value is decoded as 1 and otherwise 0) since
noise may degrade the signal to a great extend.

Digital broadcasting requires the use of a large amount of bandwidth due to
the encoding procedure involved ( i.e the modulation method, quantizing and
coding of the signal etc).  It would require a long posting to delve into
the modalities of how this is achieved, which is best left for later.

To obtain clarity of sound  with digital systems, distance is a limiting
factor and more complex circuitry is needed at the receiver to decode the
signals. The current radio sets do not have the required circuitry for
suitable reception.

In Europe, digital radio receivers are selling at around £200 - £300
per unit, which in my opinion would dent the pocket of any ordinary Gambian
whether abroad or in the Gambia.

May be in time, the cost of these units may be affordable to the masses and
only then would the justification for setting up such stations be realised.
Don't misunderstanding me on this point.  What I am trying to say is that,
if this stations are to be commercially viable, they need to reach a wide
audience, and  the only way to achieve this is if these audience can tune
in.

I think Yus would enlightened further on your questions.  However, the
basics of AM and FM (for Analog transmission) follows:

AM modulation produces two sidebands (Upper & Lower) after modulation and
both sidebands carry the same information.  sometimes one of the sideband is
suppressed to save on transmitting bandwith.  This technique is known as
Suppressed-Single-Sideband (SSB).


FM Modulation on the other hand produces a series of sidebands on both sides
of the carrier( the frequencies of these sidebands are scaled according to
their distance from the carrier ),  and since all these sidebands carry the
same information, one tends to tune get a clear reception.

I think this enlightened you on these aspect.

Thanks
Mohin















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