Making the own radio transmitter

ham-radiomixerradioRFsoftware defined radio

So I have recently been interested in Radio electronics, and I have been looking around to buy a HAM radio transmitter,but they tend to be very expensive (and you learn nothing by just buying it). So I came up with an idea, I do not know if it will work with what I have planned but that is why I am asking. my circuit diagram will tell you what you need to know.

The computer does all of the modulating with PureData (AM, FM etc.) at 10 KHz and it pipes the signal out into the mixer, where a signal from a signal generator will up convert the signal to the desired frequency. I know i didn't use the correct symbol for the filters but I didn't want to draw out the whole thing.

Would this work? If not what would it take to make it work?


simulate this circuit – Schematic created using CircuitLab

Best Answer

That would work, as the comments correctly noticed: This is a software defined radio. However, unless you plan to generate IF with your sound card (which you most likely aren't doing, since sound cards, even ones that support 192kHz sampling rate, aren't frequency flat for a large range), you will only be able to generate carrier-symmetrical spectra with a real-valued baseband signal (for the ham in you: no SSB!); what you want is to be able to mix up one signal with a cosine @ f_carrier, and one with a sine @ f_carrier (notice the phase shift); that would be called IQ mixing. You can actually do that, and there are commercial, non-commercial and half-commercial solutions out there that implement that for you.

Now, a sound card's bandwidth is not really large, so as soon as you start investing yourself much in this, you might find it unsatisfactory, but for a start, what you're planning is definitely possible.