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FCC rules won't allow encryption. I'm not sure why the rules were made originally.

tjohns 5y ago
Ham radio relies on self-policing within the community to ensure compliance with the rules - the biggest one being "no commercial use". The "no commercial use" rule ensures companies aren't using the limited ham radio spectrum as a workaround to getting their own dedicated license and frequency allocation. If encryption were allowed, there'd be no way for other users to verify whether traffic is commercial or not.
- alibarber 5y ago
  I always thought that encryption not being allowed was a way to discourage illegal commercial use of it. No business wants their comms in the clear with no means of verifying the sender of the message - so ham radio would be useless to them.
  - fragmede 5y ago
    But even not-for-business, I don't want someone else to be able to impersonate others, so signatures/verification still needs to be supported. Otherwise someone who's good at voice impersonations of others could wreak havok.
    - tjohns 5y ago
      There is no rule against using digital signatures for authentication. Your actual message just has to be in the clear. The exact wording is in 97.113: "No amateur station shall transmit... messages encoded for the purpose of obscuring their meaning".
Enginerrrd 5y ago
Because way back when long range radio was a plausible way for spies to communicate back to the homeland.
giantrobot 5y ago
Encryption is indistinguishable from noise. So the difference between a high power encrypted transmission and high power jammer is semantic. Radio transmissions also propagate. Sometimes they propagate in unexpected ways reaching much farther than expected. If you combine these things you end up with encrypted transmissions raising the noise floor for everyone in a band with no way to know if that noise is a transmission or actual noise. A lot of ham bands are already very noisy from natural sources, a bunch of encrypted transmissions increasing the noise floor just serves to make those bands inaccessible. The propagation makes this problem even worse because encrypted transmissions can raise the noise floor for hams hundreds or even thousands of miles away. Even if an encrypted transmission uses a very narrow bandwidth (no worse than other digital modes) you're still monopolizing part of a very small band with a private conversation preventing others from using the shared resource. To make matters worse encryption necessitates some form of error correction. Whether this is forward error correction, retransmission, or whatever it's necessary for a receiver to receive a correct ciphertext in order to decrypt a message. Error correction necessitates a higher duty cycle in order to send the error correcting overhead. So encrypted transmissions last longer than the equivalent unencrypted digital mode tying up limited bandwidth for a longer duration.
- trcarney 5y ago
  > Encryption is indistinguishable from noise. So the difference between a high power encrypted transmission and high power jammer is semantic The difference, from an RF perspective, of an encrypted signal and a non encrypted signal is non-existent as the encryption takes place before the modulator. Therefore encrypted signals won't impact the noise flow for everyone in the band. This would only occur if the operator were using frequency hopping. >you're still monopolizing part of a very small band with a private conversation preventing others from using the shared resource Depending on the technology used in the receiver, this also isn't true. There are numerous techniques to allow for multiple carriers on the same band. CDMA for example would allow for this. It would take some coordination to make sure each carrier is using a different code but should be feasible for amateur radio operators. It all depends on how sophisticated their receiver is. >Error correction necessitates a higher duty cycle This is true and is why encrypted signals have lower data rates. So instead of having a longer transmission you lower the data rate to get the same effect.

Ham radio relies on self-policing within the community to ensure compliance with the rules - the biggest one being "no commercial use". The "no commercial use" rule ensures companies aren't using the limited ham radio spectrum as a workaround to getting their own dedicated license and frequency allocation. If encryption were allowed, there'd be no way for other users to verify whether traffic is commercial or not.

alibarber 5y ago
I always thought that encryption not being allowed was a way to discourage illegal commercial use of it. No business wants their comms in the clear with no means of verifying the sender of the message - so ham radio would be useless to them.
- fragmede 5y ago
  But even not-for-business, I don't want someone else to be able to impersonate others, so signatures/verification still needs to be supported. Otherwise someone who's good at voice impersonations of others could wreak havok.
  - tjohns 5y ago
    There is no rule against using digital signatures for authentication. Your actual message just has to be in the clear. The exact wording is in 97.113: "No amateur station shall transmit... messages encoded for the purpose of obscuring their meaning".

Enginerrrd 5y ago

Because way back when long range radio was a plausible way for spies to communicate back to the homeland.

giantrobot 5y ago

Encryption is indistinguishable from noise. So the difference between a high power encrypted transmission and high power jammer is semantic. Radio transmissions also propagate. Sometimes they propagate in unexpected ways reaching much farther than expected. If you combine these things you end up with encrypted transmissions raising the noise floor for everyone in a band with no way to know if that noise is a transmission or actual noise. A lot of ham bands are already very noisy from natural sources, a bunch of encrypted transmissions increasing the noise floor just serves to make those bands inaccessible. The propagation makes this problem even worse because encrypted transmissions can raise the noise floor for hams hundreds or even thousands of miles away. Even if an encrypted transmission uses a very narrow bandwidth (no worse than other digital modes) you're still monopolizing part of a very small band with a private conversation preventing others from using the shared resource. To make matters worse encryption necessitates some form of error correction. Whether this is forward error correction, retransmission, or whatever it's necessary for a receiver to receive a correct ciphertext in order to decrypt a message. Error correction necessitates a higher duty cycle in order to send the error correcting overhead. So encrypted transmissions last longer than the equivalent unencrypted digital mode tying up limited bandwidth for a longer duration.

trcarney 5y ago
> Encryption is indistinguishable from noise. So the difference between a high power encrypted transmission and high power jammer is semantic The difference, from an RF perspective, of an encrypted signal and a non encrypted signal is non-existent as the encryption takes place before the modulator. Therefore encrypted signals won't impact the noise flow for everyone in the band. This would only occur if the operator were using frequency hopping. >you're still monopolizing part of a very small band with a private conversation preventing others from using the shared resource Depending on the technology used in the receiver, this also isn't true. There are numerous techniques to allow for multiple carriers on the same band. CDMA for example would allow for this. It would take some coordination to make sure each carrier is using a different code but should be feasible for amateur radio operators. It all depends on how sophisticated their receiver is. >Error correction necessitates a higher duty cycle This is true and is why encrypted signals have lower data rates. So instead of having a longer transmission you lower the data rate to get the same effect.