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Serial Port SDR

hackaday.com

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Re: Serial Port SDR

#11

Post by krallja »

apo wrote: post #7

It sounds interesting. Beyond controlling RC vehicles, what would be some applications of software defined radios (SDRs)? By the way, it looks like a USB-VGA dongle can be manipulated in a similar way: https://news.ycombinator.com/item?id=16907260

AM & FM audio transmission

Amateur TV

Ham radio

Point-to-point communication

Radio telescopy

Receiving satellite signals

Lots of opportunities to reverse engineer existing signals

Re: Serial Port SDR

#12

Post by IIAOPSW »

Well now we know what radio waves are produced by 0x55. How about other characters? I'm willing to bet that everyone's wired keyboard is an SDR so to speak and a well placed receiver can keylog you.

Re: Serial Port SDR

#14

Post by sokoloff »

Fordec wrote: post #9
rsp1984 wrote: post #3

Can someone with understanding of the matter ELI5 why this matters?

Without having to hack and/or expose I/O pins, anything with a USB port that can run the open source code can be given wireless communication capabilities with a very common and cheap chip

With the tradeoff of being incredibly disruptive to the RF spectrum (and therefore strongly ill-advised for use in a product)

Re: Serial Port SDR

#15

Post by vtesucks »

I have a converter that I plug into my USB socket and then I can plug my old style keyboard into this converter. Is that what is being talked about here? The picture looks different.

Re: Serial Port SDR

#16

Post by jimmytucson »

lima wrote: post #10

> This alone is impressive, but [Ted] isn’t done yet. He realized that this method of transmission was generating some strong frequency harmonics which extended far beyond the theoretical maximum 1 MHz frequency of his UART SDR. i.e., blast noise all over the spectrum. There's a reason why real transmitters are more expensive than a serial port adapter. This kind of RF pollution is illegal for obvious reasons and if…

I don't think transmitters are made artificially expensive to keep out the newbs. As you said, it's illegal.

And if you're a newb (like me) interested enough to try this at home, you might have read to the end of the article where it states:

> DISCLAIMER: It should go without saying that you should never transmit on any frequencies or at any power levels for which you are not authorized by the local governing body, but I guess I just said it anyway.

Re: Serial Port SDR

#17

Post by poizan42 »

lima wrote: post #10

> This alone is impressive, but [Ted] isn’t done yet. He realized that this method of transmission was generating some strong frequency harmonics which extended far beyond the theoretical maximum 1 MHz frequency of his UART SDR. i.e., blast noise all over the spectrum. There's a reason why real transmitters are more expensive than a serial port adapter. This kind of RF pollution is illegal for obvious reasons and if…

But he doesn't have any amplification. Nothing is happening here that doesn't happen already with normal use of the UART. If what he is doing here is illegal then the RF pollution from using the UART normally would be too.

Re: Serial Port SDR

#18

Post by rkachowski »

lima wrote: post #10

> This alone is impressive, but [Ted] isn’t done yet. He realized that this method of transmission was generating some strong frequency harmonics which extended far beyond the theoretical maximum 1 MHz frequency of his UART SDR. i.e., blast noise all over the spectrum. There's a reason why real transmitters are more expensive than a serial port adapter. This kind of RF pollution is illegal for obvious reasons and if…

From the article, the effective range seems to be around 10 feet.

IIRC you are generally permitted to use whatever frequency you wish within a very limited radius as long as it is for "research purposes"

Edit: this last point is wrong, as mentioned below exemptions seem to apply for certain frequencies with a low powered device https://www.fcc.gov/media/radio/low-power-radio-general-info...

Re: Serial Port SDR

#19

Post by bluGill »

IIAOPSW wrote: post #12

Well now we know what radio waves are produced by 0x55. How about other characters? I'm willing to bet that everyone's wired keyboard is an SDR so to speak and a well placed receiver can keylog you.

Most keyboards don't have an antenna attached. While you can keylog a keyboard via emissions like this, you have to have physical access to the office to do so - at that point putting a usb keylogger inline with the keyboard is easier and more reliable. (or substitution your own keyboard with a real radio)
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