Thank you Carlos, a useful answer. I am rather new to this SDR thing and have a really newby question. Where in the chain between antenna and speaker should the signal be sampled by an SDR? The Nyquist limit imposes a sample rate of at least twice the highest frequency component so if you want to sample at the input RF and that RF is 29 MHz then you need a sample rate of 58 MHz which is not only pretty fast but will also produce a LOT of data very quickly. On the other hand if you mix it down to a first IF you lose the possibility of digitally filtering out unwanted signals earlier in the signal path before they have a chance to overload something.
As with nearly everything in engineering it is a trade-off. But where do most SDR's do the sampling? On Wed, May 14, 2008 at 7:33 AM, i2phd <[EMAIL PROTECTED]> wrote: > --- In [email protected] <soft_radio%40yahoogroups.com>, > "Carlos Vargas Vidal" > <[EMAIL PROTECTED]> wrote: > > > > My question is the following. Can I use the "digitalized" signal, if > > possible, with a simple SDR program or software? That is, by > > connecting the DSP to a computer as an analog digital converter (ADC). > > Carlos, > > in principle, yes. Practically it is not so simple. You have the > data digitized by the ADC chip present in that box. Now you have to > input those digital data into the PC. How ? If the sampling frequency > is not too high you could use the (now obsolete) parallel port. Or the > USB port. Or a FireWire port. Or an Ethernet port. In any case you > have to write the code to handle that flow of data, and to pass them > to the SDR program of your choice. Don't expect to find a ready-made > SDR program that does that for you, AFAIK there are none. If you want > to use Winrad, as an example, you should write an interfacing DLL that > contains all the technicalities needed to "talk" with one of those > communication ports, and which then will pass the received data to > Winrad itself. > > 73 Alberto I2PHD > > > -- Patricia Wilson Apache Junction, AZ Member NRA, BMWMOA, AMA, ARRL WB8DXX BMW '06 R1200RT "Graues Gespenst"
