4 ms·

Tangent 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 imme

by ge96 1y ago

Tangent 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 1y 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 1y 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 1y 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 1y 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/ https://www.sigidwiki.com/ -- which has been helpful to ID all the fun stuff you can see with RTLSDR
      - iancmceachern 1y ago
        Delicious, 2.5 mile long antennas behind airplanes Corona, stuff like this, the sheer gall, it's impressive.
        janzer 1y ago
        Sadly the 6000 mile antenna never got built, but they did get a few tens of mile long ones built. https://en.wikipedia.org/wiki/Project_Sanguine https://en.wikipedia.org/wiki/Project_Sanguine
      - mschuster91 1y ago
        The cost of that must be insane - the price tag of being about the only military force on this rock capable of projecting force and delivering utter devastation 24/7/365 any place any time even if the entirety of the US got glassed.
deleted 1y ago
[deleted]
mmmlinux 1y ago
was the submarine remote RF or IR?
- ge96 1y ago
  it's RF this one https://www.dhgate.com/goods/822484606.html https://www.dhgate.com/goods/822484606.html seawolf Omnibearing RC Submarine - 6CH 35cm Walmart used to sell it like 17 years ago
davemp 1y ago
Water attenuates (reduces the power of) signals significantly and more-so at higher frequencies. The HF (3-30MHz) band is definitely not what you’d want to pick (sonar is in the KHz range). The sub was probably still 27MHz but just higher power with a better antenna because of the FCC regulations though.

by ge96 1y ago

doug_life 1y 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 1y 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 1y 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 1y 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/ https://www.sigidwiki.com/ -- which has been helpful to ID all the fun stuff you can see with RTLSDR
    - iancmceachern 1y ago
      Delicious, 2.5 mile long antennas behind airplanes Corona, stuff like this, the sheer gall, it's impressive.
      - janzer 1y ago
        Sadly the 6000 mile antenna never got built, but they did get a few tens of mile long ones built. https://en.wikipedia.org/wiki/Project_Sanguine https://en.wikipedia.org/wiki/Project_Sanguine
    - mschuster91 1y ago
      The cost of that must be insane - the price tag of being about the only military force on this rock capable of projecting force and delivering utter devastation 24/7/365 any place any time even if the entirety of the US got glassed.

deleted 1y ago

[deleted]

mmmlinux 1y ago

was the submarine remote RF or IR?

ge96 1y ago
it's RF this one https://www.dhgate.com/goods/822484606.html https://www.dhgate.com/goods/822484606.html seawolf Omnibearing RC Submarine - 6CH 35cm Walmart used to sell it like 17 years ago

davemp 1y ago

Water attenuates (reduces the power of) signals significantly and more-so at higher frequencies. The HF (3-30MHz) band is definitely not what you’d want to pick (sonar is in the KHz range). The sub was probably still 27MHz but just higher power with a better antenna because of the FCC regulations though.