Hi Jim,
Can't remember that clearly, but the idea is to get the 2nd sound IF of the
TV/FM tuner capacitively to one of the ADC inputs. The IF pin is one of the
TV/FM tuner output pin. (It might not be available in all tuner module). I
removed the existing circuit that was attached to this IF pin, in my case, I
just need to removed a 0 ohm resistor. I also resisitively divide the IF pin
output voltage just enough so that it does not exceed CX23881 voltage level.
This step might be redundant since I do not have a oscilloscope to measure the
IF pin voltage swing.
The sine came from a program written for Palm Pilot. Looking back at the
code, I guess its about 2k. You can inject the tone direct to the composite
video in and use the CX built in multiplexer to select this input.
Regards,
Hew
Jim Perkins <[EMAIL PROTECTED]> wrote:
Hew,
Do you recall what the hardware mods were? I'm wondering if I can clean up
card with caps here and there. I looked at your sine wave data. I low pass
filtered it and got rid of most of that garbage. The tone is at 1890 Hz as far
as I can tell. How did you generate that tone and what was the center
frequency? Where did you inject the tone?
-Jim
Hew How Chee wrote: Hi Jim,
The card I use last time is PV-TV304P+ (REV .2B) with FMRC (FM and Remote
Control) . The chipset used is CX23881. The card from newegg.com is using
CX23883. Can't tell it is compatible or not. The data I got is 8 bit unsigned.
Didn't try out 10 bit since I was quite dissapointed by the noise in the 8 bit
digitized signal. Nevertheless, it is still possbile to digitize the 10.7 MHz
FM IF with hardware mods.
Note that the source code at http://www.geocities.com/how_chee/cx23881.htm
can't compile and run in Linux kernel 2.6 and is not hooked up to GNURadio. It
was developed using Knoppix Live CD 3.4 running kernel 2.4.x.
Best regards,
Hew
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