Electronics > RF, Microwave, Ham Radio

Simple SDR transmitter?

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rwgast_lowlevellogicdesin:
Iv'e been searching the internet for an SDR transmitter project but surprisingly I haven't found one. I was thinking that all you really need to do is use GNU radio to build the modulated signal and then play it out you sound card in to a mixer controlled by a DDS or VCO straight in to an amplifier/antenna. Could it really be this simple. I would assume if it was people would be making and selling little circuits like these everywhere, to pair with an RTL dongle.

Kind off topic but how does the pi tx software do its thing without hardware to generate the carrier wave? It says it can transmit up to 700mhz but I know the pi cant flip pins that quick?

Earendil:
Yes, theoretically that's it. However I'm not convinced that it's practical to create an add-on for SDRs that's not designed to be used as a transmitter. Usually these are single (or 2) chip solutions. I don't expect that you can reuse many things from the circuit. Probably you'll be developing a complete transmitter.

HackRF can transmit btw. I'm pretty sure that some high-end SDRs can transmit too, but I haven't used any of them.

Gecko:
Have you seen the red pitaya SDR apps?
The frequency region (0..30MHz or so) you can use it on is very interesting for Ham radio I think. (At least in my opinion).

rwgast_lowlevellogicdesin:
ya but that stuff is way to much!!! I mean buy a 10 dollar dongle, buy or make an upconverter/downconverter and you get DC-4ghz range. Then use GNU radio to modulate signal send that out your sound card in to a two dollar mini cirucits ade-1 mixer and mix it with a mini circuits POS 150 VCO and you are able to broadcast in to the whole 2m band along with the airline and commercial FM bands. You could use a DDS with a PLL to get a whole 1-4ghz transmit.

Basically it would be like the hack-rf for a ton less money. Adding LNA's and preselecting would probably give you a signal as clean as an airspy. you could build this for under 70 dollars.

1design:
Do it! ;)

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