Pos-150

savnik · May 18, 2007

I use POS-150 as oscillator for FM band (87.5-108 MHZ).
When modulate the oscillator with a MPX sound it plays well but does not make segregation in the channels , if I receive the oscillator with a stereo radio for Fm band. Only turn on the LED which is for to show when the station is stereo.
Why happen it ;

savnik · May 19, 2007

Anyone to have used the POS-150

Nigel Goodwin · May 19, 2007

As you don't even mention what it is?, and google doesn't find anything on the first page either, it seems a pretty vague question!.

JimB · May 19, 2007

savnik said:
I use POS-150 as oscillator for FM band (87.5-108 MHZ).

The POS-150 is a voltage controlled oscillator from Mini-Circuits.

savnik said:
When modulate the oscillator with a MPX sound it plays well but does not make segregation in the channels , if I receive the oscillator with a stereo radio for Fm band. Only turn on the LED which is for to show when the station is stereo.
Why happen it ;

It all depends what you mean by "MPX sound"?
I assume you mean a multiplex stereo signal.
How are you generating that multipexed signal?
Does it have the 38kHz (or is it 19khz?) pilot tone? If not the LED in the receiver won't illuminate.

JimB

savnik · May 19, 2007

JimB said:
The POS-150 is a voltage controlled oscillator from Mini-Circuits.

Yes

JimB said:
I assume you mean a multiplex stereo signal.
How are you generating that multipexed signal?
Does it have the 38kHz (or is it 19khz?) pilot tone? If not the LED in the receiver won't illuminate.

Yes , I mean a multiplex stereo signal and generate with stereo encoder( pilot tone is 19khz)

audioguru · May 19, 2007

Its modulation bandwidth is too narrow for FM stereo because it has an output down 3dB at 100kHz bandwidth. It must be absolutely flat to 38kHz for low audio frequencies stereo and it must be absolutely flat to 53kHz for audio frequencies up to 15kHz stereo.

It might work well for mono FM.

Here is a site "Stereo Multiplexing for Dummies" that explains it all:
https://members.tripod.com/~transmitters/stereo.htm

savnik · May 19, 2007

audioguru said:
Its modulation bandwidth is too narrow for FM stereo because it has an output down 3dB at 100kHz bandwidth.

3 dB MOD.
BANDWIDTH
(kHz)
100

Is from datasheet.Can you explain more to understand what mean;

Nigel Goodwin · May 19, 2007

FM stereo requires 300KHz bandwidth (if I recall correctly?), that's only got a third of what's required.

audioguru · May 19, 2007

In the "good old days" when an FM receiver's IF amplifier had a bandwidth that was too narrow for good separation of multiplexed stereo channels, an RC circuit was used in the audio path to boost the high frequencies up to 53kHz so that the response was flat. Then the stereo separation was very much improved.
I wonder how much it would help this RF transmitter.

savnik · May 20, 2007

Nigel Goodwin said:
FM stereo requires 300KHz bandwidth (if I recall correctly?), that's only got a third of what's required.

The FM bandwidth is 150 KHz

Nigel Goodwin said:
In the "good old days" when an FM receiver's IF amplifier had a bandwidth that was too narrow for good separation of multiplexed stereo channels, an RC circuit was used in the audio path to boost the high frequencies up to 53kHz so that the response was flat. Then the stereo separation was very much improved.
I wonder how much it would help this RF transmitter.

I don't believe to work , so i will try.

Lou Dorren · Sep 17, 2007

The mini circuits pos series of VCO can not be modulated by frequencies much over 10 KHz. This is because the is internally a large bypass capacitor (.1 uF) directly on the control voltage pin to ground. This is the reason you are having problems.

Lou Dorren

Hero999 · Sep 18, 2007

Thanks for posting but it's a bit late now as this thread is five months old.

chemelec · Aug 18, 2009

This is an Old Article, But I just purchased one of these "Mini-Circuits", POS-150 Modules.
(I Bought it On Sale for $4.00)

Talk about a Nice Chip for a Simple and Small FM Transmitter.
I'm Quite Impressed on its Frequency range (75 to 150 Mhz) and good Stability.

Haven't checked out What range I can get yet, But I will.

Pos-150

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