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Transmitting FM, AM, SSB, SSTV and FSQ with Just a Raspberry Pi

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Re: Transmitting FM, AM, SSB, SSTV and FSQ with Just a Raspberry Pi

#12

Post by therealidiot »

themodelplumber wrote: post #11
callesgg wrote: post #10

I am slightly confused by the screen-shot of an ubuntu OS with a windows XP desktop. :)

Yeah, how...what is that?

I think it's called 'fusion' or something in VMWare, and in VirtualBox it's called seamless mode

Re: Transmitting FM, AM, SSB, SSTV and FSQ with Just a Raspberry Pi

#13

Post by GFK_of_xmaspast »

Kliment wrote: post #6
makomk wrote: post #5

Earlier quoted context omitted.

Harmonics are trivial to filter - they're at multiples of the fundamental frequency, so 100MHz, 150MHz, and so on. You can just stick a lowpass filter on the output and it'll block all the harmonics because they're so far away from the fundamental. Unfortunately, the waterfall appears to show strong spurs every 30 Hz, and those would be ridiculously difficult to filter out. I think the normal solution is to design yo…

Given how regularly spaced they are they might be other channels (regular TV maybe?)

It looks like they're spaced at 30KHz, which seems to me to be a very tight grouping for any kind of transmission like that (and presumably if that band was that crowded to begin with, the author would have picked a different one).

Re: Transmitting FM, AM, SSB, SSTV and FSQ with Just a Raspberry Pi

#16

Post by AstroJetson »

pi-rat wrote: post #7

Very cool, but please don't do this without a proper filter, you're spewing garbage all over the spectrum.

Right, but narrow passband filters are not that hard to make.

I see this as a way to get more experimenters to be hams. It also makes it much easier to demo explain / teach / get people excited about SDR and what you can do with them.

Re: Transmitting FM, AM, SSB, SSTV and FSQ with Just a Raspberry Pi

#18

Post by jjoonathan »

bajsejohannes wrote: post #17

> all you need to do is plug in a wire antenna Just to make sure I get this right, a "wire antenna" is just a wire, right?

If it doesn't have the right length, impedance, and possibly orientation it's going to be significantly less effective. Even at this scale it probably makes sense to distinguish a wire antenna from a wire on that basis.

For more powerful equipment getting the wrong wire geometry could melt your expensive setup and get you in trouble with the FCC, so it makes even more sense to tack on the word "antenna" to mean "I've thought about this chunk of metal outside the DC approximation."

Re: Transmitting FM, AM, SSB, SSTV and FSQ with Just a Raspberry Pi

#19

Post by Animats »

In working with RF, the test gear you need to see what's going on costs far more than the radio gear itself. The prices go way up as you get into the GHz range.

There's a lot of filter adjustment, antenna tuning, and shielding placement as you look at a spectrum analyzer and see spikes that shouldn't be there. This is why there are little RF modules in cans for many applications. Someone already did that work for you. Some vendors: [1][2]

[1] http://www.rfdigital.com/ [2] https://www.linxtechnologies.com/en/products/modules

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