71–80 of 91 posts
Earlier quoted context omitted.
Multiples of 1/4 wavelengths, and if built properly 5/8 wave.
... but 5/8 isn't a multiple of 1/4, Or is that not what you meant?
Now, you can actually make almost any length work with proper tuning circuitry, but the ones mentioned are the most effective.
As mentioned in the first sentence, the RTL-SDR project is out there. You can easily buy a $20 USB Software Defined Radio with software that will handle everything for you and lets you play around with an SDR: https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/
For roughly the same price there are some DVR boards that could be converted to SDR operation once they're hacked. They already use embedded Linux although no source is provided. https://www.aliexpress.com/item/OUERTECH-5-in-1-AHD-CVI-TVI-...
https://www.aliexpress.com/item/HackRF-One-1MHz-to-6GHz-SDR-...
> 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…
It's not.
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.
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.
An interesting thing from reading about practical experiments in EM eavesdropping is that it's not just the obvious emanations that you have to worry about. Your sidechannels have sidechannels. In that paper, for example, the actual communication radiates and can be received in the shortwave band, but also a frequency-modulated version of it appears in the FM radio band. Presumably a bit of power-supply droop is modulating a local oscillator causing it to transmit a clear signal.
Not very impressed then as we are sitting there nights and days.
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Wires connected to a closed circuit will radiate too, if you drive them at high frequency. Maybe not efficiently , but it'll still radiate. There's nothing special about an open circuit that makes an antenna work. Shielding (e.g. coax, or a properly grounded enclosure) is what prevents ordinary wires from becoming antennas.
Normal rs232 is run through shielded cables as well. It was standard practice to wire the d-sub connectors to the cable shields. The wires themselves may not have been shielded, but the cable was shielded against being an antenna.
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)
What about meter long wire that runs from the keyboard to the back of the tower.
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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, b…
Transmitters are not even expensive. A Baofeng is around $20. Some CW kits are $5.