Hi
I was fortunate to have access to a good deviation
meter so this helped me initially setup things
correctly however I appreciate few operators are in
this position.My suggestion is that they play a track
of hevily recorded programme ,wind up the input level
control on the TX until distortion is noticed then
back off the input control to the point where the
distortion just disappears.My suggestion is that any
limiter/compressor can be set up playing the same
heavy track and setting the input to the compressor
until it is compressing the required amount on
programme peaks (I set to 2db)and then adjust the
output of the compressor to modulate the transmitter
to a little below the previously set point and then
enjoy!
Not entirely scientific but a practical way of doing
it in lieu of test gear such as an audio osc and
deviation meter.
--- "Groove 107.7FM" <dean.c@...> wrote:


---------------------------------
Yep, it comes back to the tx being set up correctly.

Dean

Quoting Ross Levis <ross@...>:

> You'll probably find they are over deviating with
the modulation, as
> well as using more than 5 watts already. The higher
the modulation the
> wider the bandwidth, Generally most LPFM operators
have no clues how
> much audio to feed into the transmitter and guess
based on the volume of
> the commercial stations. But the commercial stations
have highly
> compressed audio just sitting under on the standard
deviation of 75khz,
> and to get this volume from non-compressed audio
requires massive over
> deviation.
>
> The extra power does not increase the bandwidth as
such. The strength of
> the signal being received in the radio will make it
appear wider, but 2
> stations at 0.2Mhz separation will work just as well
at 0.5 or 5 watts
> in the same area, both not very well. 0.3Mhz is the
minimum really.
>
> Ross.
> ----- Original Message -----
> From: alnairgrus
> To: LPFM_Radio@...
> Sent: Monday, December 12, 2005 11:20 AM
> Subject: [LPFM] 5 watts in the city
>
>
> Just one question.Why go 5W in the city...fair
enough in rural areas
> but isnt LPFM supposed to be local?
> It will wipe out anything whatever that has a lot
smaller coverage
> areas.
>
> At present theres stations on the upper band in
Auckland that cover
> almost the whole of Auckland and one of them that
splatters about
> 300khz eitherside on a standard radio at 500mW and
over a large
> coverage area.Imagine at 5 watts it will wipe the
band.
> Just my thoughts.
>
> Michael
>



Groove 107.7FM
PO Box 10-989
The Terrace
Wellington
Ph 04-381 GROOVE


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