Re: W-FM


Russ Hines <russ@...>
 

Thanks for the reply, Jose.� I choose "not." ;-)

You're right, opinions are like arses, everyone has one.� I just disagreed with yours as yours aren't based on fact.� You tell us what "everyone knows," yet display a lack of understanding of a multiplexed FM signal.

IMHO, that proves a lot, I am sorry.� Try Wikipedia, they have a pretty good explanation of broadcast FM.

73,
Russ
WB8ZCC


On 1/4/2011 7:39 PM, jose maria trueba wrote:

�

Yes, everybody knows that our FM is +/5KHz deviation and 2.5 being the narrow mode.
No secret either that AM station channels are every 10KHz in the U.S. and 9KHz in Europe. Right!

Nice to find a colleague here. I am working for a broadcast radio, FM and AM and TV, since 1983. Not 30 years yet! You worked longer, but that not proves much, I am sorry.

My numbers are right, believe or not. Just check a good FM receiver, if you don't believe it. Take just one of your RF generators and check bandwidths. You can even open the lid of the receiver and read filter numbers. And think about it twice, this time.

2011/1/4 Russ Hines <russ@...>
�

Well, having worked as a broadcast engineer in the U.S. for nearly the last 30 years, all I can say is... HUH?!?!?� I have no idea what Jose's been smokin', but it must be REALLY good. ;-)

I'm into versatility, but there is such a thing called "mission creep," and I'm guessing that's where this is going.�

For communications purposes, deviation for FM is +/-5kHz is wide, +/- 2.5kHz is narrow.� IMHO, 6kHz should work just dandy for both full-carrier AM and wide FM.

But if you really want to include it, then for U.S. broadcast, the channels for FM are 200kHz wide, max modulating frequency is 15kHz, 100% modulation is +/- 75kHz deviation, and all subcarriers are AM modulated.� For the AM broadcast band, the channels are 10kHz wide, max modulating frequency is about 5kHz.� Now that's assuming you don't incorporate IBOC "HD" radio that you wouldn't be able to include anyway unless you paid a horrendous licensing fee to Ibiquity.

But if you're willing to go that far, how about a incorporating an ATSC/DVB/COFDM/16QAM/64QAM/FLO digital television demod?�

See where mission creep can lead you. ;-)

Simon, your SDR Console is a really nice, useful communications tool for SDR enthusiasts, not a table top radio/stereo/MP3/8-track player/alarm-clock/coffee-maker.� I wouldn't worry trying to make it all things to all people because no one will ever be satisfied, and a once-useful tool with promise will become bloated and impossible to use.

Again, just IMHO.

73,
Russ
WB8ZCC

On 1/4/2011 3:03 PM, jose maria trueba wrote:
�

Hi,

75KHz is the nominal frequency deviation of a FM mono broadcast transmission, but now all of them are using stereo mode, adding two 38KHz sub-carriers. Mode is called 256-f3 because (75dev+38stereo+15max_audio_freq)x2 equals 256, nominal bandwidth.

Later they came with RDS, sub-carrier is at 57KHz, resulting a max bandwidth of� (57+75)x2 equal to 264, and filters should be as wide 280KHz. There are some 330KHz filters to be used in cascade with another one. I imagine that some are that wide to give a margin for some over-deviating transmissions.

Let us say that 280KHz@-6dB is a reasonable bandwidth.

73's
Jose

2011/1/4 Simon HB9DRV <simon@...>
�

Hi,

�

No �I�ll maybe add it very soon but need help!

�

What bandwidths are needed? For broadcast I think it�s 100kHz, anyway let me know what typical bandwidths are needed please.

�

You never know � I may even add stereo J

�

Simon HB9DRV

http://sdr-radio.com

�

From: sdr-radio-com@... [mailto:sdr-radio-com@...] On Behalf Of Rob M0TFO
Sent: 04 January 2011 20:10
To: sdr-radio-com@...
Subject: [sdr-radio-com] W-FM

�

�

I may of just missed it,but does sdr-radio support Wide FM?
Rob



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