I had an rc submarine that could go underwater a couple feet, but I'd take an rc car's 27MHz radio and put it underwater, it'd stop working almost immediately soon as it went underwater (waterproofed). Wonder what the difference was.
doug_life•4h ago
It is likely that that the sub had it's antenna tuned to work well in water while the RC car antenna was tuned for open air. The two different mediums will change the antenna impedance.
ge96•4h ago
Interesting does say shorter antenna, I could see that, I think the RC sub's antenna was like 4in long vs. an rc car's antenna that's usually like a foot
iancmceachern•2h ago
Yeah, my basic understanding of submarine communications is that lower frequencies penetrate the water better. Lower wavelength needs a longer antenna. The system US subs use is a very low frequency from what I understand.
jasonjayr•2h ago
> TACAMO (take charge and move out) is the back up communications system to the US nuclear submarine fleet in case an attack on land based transmitters disables them. A rotating fleet of Navy E6 jets equipped with 200 KW transmitters and two 2½-mile-long trailing wire antennas (TWA) at 35,000 ft altitude to provide 24/7 coverage. Short pings are transmitted every few seconds.
Regarding "longer antenna" for submarines... -- I recently learned about this signal from https://www.sigidwiki.com/ -- which has been helpful to ID all the fun stuff you can see with RTLSDR
iancmceachern•1h ago
Delicious, 2.5 mile long antennas behind airplanes
Corona, stuff like this, the sheer gall, it's impressive.
Peteragain•3h ago
Software defined radio but what is LTR?
papercrane•3h ago
I believe the RTL in RTL-SDR is "Realtek Limited", the manufacturer of the chips used in the early days of SDR. I don't think the chips these days are exclusively Realtek, but the name has persisted.
jandrese•3h ago
The original low cost SDR was a European TV tuner USB stick. A driver developer noticed that it was possible to turn off the built-in vertical and horizontal blank suppression to get a raw I/Q dump from a device that was available for $20 retail. This revolutionized the hobbyist SDR community as the purpose built devices cost hundreds or thousands of dollars.
The "RTL" came from the company that built the hackable chip: Realtek.
RicoElectrico•1h ago
> A driver developer noticed that it was possible to turn off the built-in vertical and horizontal blank suppression
Aren't you confusing that with Fresco Logic USB to VGA?
ge96•4h ago
I had an rc submarine that could go underwater a couple feet, but I'd take an rc car's 27MHz radio and put it underwater, it'd stop working almost immediately soon as it went underwater (waterproofed). Wonder what the difference was.
doug_life•4h ago
ge96•4h ago
iancmceachern•2h ago
jasonjayr•2h ago
Regarding "longer antenna" for submarines... -- I recently learned about this signal from https://www.sigidwiki.com/ -- which has been helpful to ID all the fun stuff you can see with RTLSDR
iancmceachern•1h ago
Corona, stuff like this, the sheer gall, it's impressive.