Need RF Demodulator for designing VHF Receiver

[erfan_fossile]

Hai All,

I wanted to design a VHF receiver with a band of 136.5MHz to 173.5MHz with 99 selectable channels and an audio output to play the baseband audio. Kindly help in finding the demodulator part and and an audio codec for the output..

Thanks,
Erfan

 

[chuckey]

You don't say what modulation you are using. A good start would be to look a what radio amateurs are doing, as they have a band at 144-146 MHz. Try googling "ARRL" (american hams) or "RSGB" (UK hams).
Frank

 

[erfan_fossile]

Hai,

I am using the below specifications and I need to design the Radio receiver for the same. Let me know if you know any modules which can do this.


Frequency band : 136 MHz to 173.5 MHz
Number of RF frequency Channels : 99
Channel separation : 375 KHz
Modulation : Wideband FM (± 105 KHz deviation)
Modulating frequency band : 10 Hz to 10 KHz (3 dB points)
Input RF sensitivity : -92dBm (minimum)
Out put S+N/N : 26 dB
Spurious rejection : 80 dB (minimum)
IF rejection : 80 dB (minimum)
Intermodulation rejection : 60 dB (minimum)
Adjacent channel rejection : 70 dB (minimum)

 

[FvM]

One would preferably expect classical analog FM according to the specification. Similar to FM broadcast, except for the frequency. But in this case, what's the purpose of a codec?

 

[chuckey]

88-108 is band 2 Broadcast Fm in the UK & Europe, this looks like band 2 1/2 (?) with non hi-fi frequency range and mono with excessive channel spacing and no pre/de-emphasis. Looks like a lost cause to me. But to get back to your question, get hold of a FM broadcast receiver and modify the front end to change the oscillator and RF frequency tuning. If you are stuck with your channel spacing it looks as though you will have to design your own PLL set up if you want to switch from channel to channel.
Frank