Re: [Discuss-gnuradio] Hardware->Mixer->Oscillator

[Ian Wraith]

Hello Saeed

>I got a TV tuner module, but as it's not a cable moden tuner; the voice
data is a FM modulated signal with a center frequency of "33.8 Mhz"  .
>
>i accordance with using a sound card (with low sampling rate),as the data
aquisition card, i have to downconvert it to a center frequency of 10 Khz,
but the specific crystal needed (33.7 Mhz) to use with NE602 mixer,  is not
available on the market.
>
>Can any one help me, or does any one have an idea of the solution?
>
>It might be a PLL, VCO, Digital VCO, ....

 You can have crystals custom made by companies for your own frequencies.
I use one here in the UK called Quartzlab (I can find you the address
if you need it) who make a crystal for just over 10 UK pounds although
that may have gone up a little. However don't forget that most TV tuners
have a wide IF stretching from around 33 MHz up to 40 MHz so just about
any frequency crystal in that range will do you.

 I don't know what kind of TV tuner you are using but be careful as many 
of them have what I consider quite a coarse tuning step of 62.5 KHz
or sometimes 100 KHz. So if you only have a 10 KHz bandwidth it may
be impossible to tune into some frequencies if the signal on them is
quite narrow.

 You have discovered that NE602's are hard to get hold of ! You could use
a SBL-1 which is a diode mixer module instead. Also depending on your
electronics skill you may want to look at the AD607 IC. Which contains
a mixer plus an I & Q output. For more details have a look at ..

http://www.analog.com/Analog_Root/productPage/productHome/0,,AD607,00.html

 I hope I have been of some help.

Regards

Ian