5 ms·

Why is it regulated anyway? What’s the balance at play? Limits?

CobaltFire 5y ago
It's limited because they don't want to create a defacto lower limit on what it costs to start using HAM bands. That said, I agree it's taking too long. The technology for the higher symbol rates is now cheap enough to be a non-issue.
pgt 5y ago
Presumably for the same reason that GPS time signals had (have?) pseudorandom noise added: to prevent an adversary from using your own systems to steer missiles with high precision.
- madengr 5y ago
  GPS uses PN codes for the timing difference measurement, as well as allowing multiple satellites on a single channel. I believe the dithering (selective availability) was turned off years ago, thus the L2 channel ads only ionospheric correction (which can also be accomplished with local sources). The FCC symbol rate limitation needs to go. It’s a hindrance on HAM radio. Just regulate it by bandwidth, or better yet EIRP PSD, but that would be tough to control.
  - jaywalk 5y ago
    Yes, Selective Availability was turned off in 2000 and will never be re-enabled. In fact, the latest generation of GPS satellites do not even support Selective Availability: https://www.gps.gov/systems/gps/modernization/sa/ https://www.gps.gov/systems/gps/modernization/sa/
- morcheeba 5y ago
  PRN (Pseudorandom noise) in the context of GPS is just a coding standard - it's just CDMA (aka Spread Spectrum) and it allows all satellite to use the same frequency. A side benefit is that the signals can be below the noise floor, and when you apply the gain from decoding, it rises the signal above the noise floor (exactly like how you can pick out a voice in a crowded bar if you know what that voice sounds like).
makomk 5y ago
There's very limited bandwidth available on most of the ham radio bands and other users don't want people taking up large chunks of bandwidth with wide, high-bitrate data signals and making the bands unusable for everyone else.
chociej 5y ago
To get one of the big things out of the way: bandwidth. The FCC don't want anyone taking up big chunks of spectrum without using a license or service appropriate to that use. Notably, they don't want a few users to be able to chew up entire bands. But there's a philosophical part to the discussion also. The tradeoff goes like this: hams get some really nice spectrum assignments, low fees, self-regulation, experimental modes and techniques, etc. In exchange, they can't use the amateur radio service commercially or for non-personal aims, and specifically they are expected to focus mostly on learning, community interaction, public service, experimentation, and so on. They also want amateur modes to be somewhat approachable, i.e. not requiring exotic or expensive hardware, necessarily. Should an operator wish to use the radio spectrum for commercial or highly productive use, especially one requiring significant bandwidth, secrecy, exclusivity, etc, they are expected to use a different license / service more appropriate to those needs. Basically: Tinkering, chit-chat, community service, narrow bandwidths => amateur radio Anything else => get a different license To that end it was long the FCC's stance that high symbol rates sort of implied that you're going outside the purposes of the amateur radio service. With digital communication having developed as much as it has, though, it's reasonable that hams want to be able to do more interesting things with digital modes, which generally means higher symbol rates.
- madengr 5y ago
  I’m wondering if you could legalese around it since a PRN is a chip, not a symbol, as the former has no information. So one could spread a low symbol rate into a high chip rate.
- burnished 5y ago
  Thanks for the additional context!
- leephillips 5y ago
  An interesting twist to the regulations is that you're not allowed to use ham radio as a substitute for cell service. I never quite understood this rule, nor how it was to be enforced; but it would seem to place some limits on the permissible chit-chat. Also: no encryption.
nomel 5y ago
Why is this downvoted? The purpose and limitations of RF bandwidth allocation isn’t exactly widely known.
- h2odragon 5y ago
  Truly. I have philosophical problems with the existence of the FCC but there's a great deal of interesting and educational discussion to be had here. At the risk of delving further into conspiracy theory I suspect that may be a reason its downvoted; because there's room for debate. There's currently a lot of feeling that once the government is involved debate must be silenced.
  - geofft 5y ago
    I didn't downvote it, but I strongly suspect it was because of the sarcasm, the meta-sarcasm, and ultimately the unwillingness to believe that interesting opposing arguments might exist. That is, the post didn't encourage interesting and educational discussion, just derision. The merit of the resulting conversation was despite the initial post, not because of it.
VLM 5y ago
Fcc part 97.101 "General Standards" (d): "No amateur operator shall willfully or maliciously interfere with or cause interference to any radio communication or signal." Pitiful we have to encode "the golden rule" of treat others like you'd have them treat you into law, but here we are its in the CFR. As of 2021 no one has a technological answer to how to avoid various wide band digital technologies from interference against, well, absolutely everything else currently in use, without forcing everyone to operate in a channelized system with massive international coordination problems. The international part is a nightmare, what if, I donno, Bulgaria refuses to channelize? Nothing will work for anyone unless everyone cooperates. Wideband digital modes do NOT play well with others. There are channelized bands around 5 mhz (in the usa) and the FCC does relax quite a bit on wide open microwave bands, but people are going to request turning all of 20 meters into one single user digital channel, and to hell with everyone else currently using the band, apparently into infinity. Its an eternal meme. I guess the best analogy I can come up with, is you can zone land as a public park for people to picnic, but that doesn't mean the land is completely lawless, if you blast your music at 160 dB the police will arrest you for preventing everyone else from enjoying their picnic. We easily right now have the technological ability to turn the 20M band into a single channel, single user, very high speed digital path at 1500 watts. But that's a terrible idea, given the zillions of current users, local and international, who would be kicked off completely unable to operate.

It's limited because they don't want to create a defacto lower limit on what it costs to start using HAM bands. That said, I agree it's taking too long. The technology for the higher symbol rates is now cheap enough to be a non-issue.

pgt 5y ago

Presumably for the same reason that GPS time signals had (have?) pseudorandom noise added: to prevent an adversary from using your own systems to steer missiles with high precision.

madengr 5y ago
GPS uses PN codes for the timing difference measurement, as well as allowing multiple satellites on a single channel. I believe the dithering (selective availability) was turned off years ago, thus the L2 channel ads only ionospheric correction (which can also be accomplished with local sources). The FCC symbol rate limitation needs to go. It’s a hindrance on HAM radio. Just regulate it by bandwidth, or better yet EIRP PSD, but that would be tough to control.
- jaywalk 5y ago
  Yes, Selective Availability was turned off in 2000 and will never be re-enabled. In fact, the latest generation of GPS satellites do not even support Selective Availability: https://www.gps.gov/systems/gps/modernization/sa/ https://www.gps.gov/systems/gps/modernization/sa/
morcheeba 5y ago
PRN (Pseudorandom noise) in the context of GPS is just a coding standard - it's just CDMA (aka Spread Spectrum) and it allows all satellite to use the same frequency. A side benefit is that the signals can be below the noise floor, and when you apply the gain from decoding, it rises the signal above the noise floor (exactly like how you can pick out a voice in a crowded bar if you know what that voice sounds like).

makomk 5y ago

There's very limited bandwidth available on most of the ham radio bands and other users don't want people taking up large chunks of bandwidth with wide, high-bitrate data signals and making the bands unusable for everyone else.

chociej 5y ago

To get one of the big things out of the way: bandwidth. The FCC don't want anyone taking up big chunks of spectrum without using a license or service appropriate to that use. Notably, they don't want a few users to be able to chew up entire bands. But there's a philosophical part to the discussion also. The tradeoff goes like this: hams get some really nice spectrum assignments, low fees, self-regulation, experimental modes and techniques, etc. In exchange, they can't use the amateur radio service commercially or for non-personal aims, and specifically they are expected to focus mostly on learning, community interaction, public service, experimentation, and so on. They also want amateur modes to be somewhat approachable, i.e. not requiring exotic or expensive hardware, necessarily. Should an operator wish to use the radio spectrum for commercial or highly productive use, especially one requiring significant bandwidth, secrecy, exclusivity, etc, they are expected to use a different license / service more appropriate to those needs. Basically: Tinkering, chit-chat, community service, narrow bandwidths => amateur radio Anything else => get a different license To that end it was long the FCC's stance that high symbol rates sort of implied that you're going outside the purposes of the amateur radio service. With digital communication having developed as much as it has, though, it's reasonable that hams want to be able to do more interesting things with digital modes, which generally means higher symbol rates.

madengr 5y ago
I’m wondering if you could legalese around it since a PRN is a chip, not a symbol, as the former has no information. So one could spread a low symbol rate into a high chip rate.
burnished 5y ago
Thanks for the additional context!
leephillips 5y ago
An interesting twist to the regulations is that you're not allowed to use ham radio as a substitute for cell service. I never quite understood this rule, nor how it was to be enforced; but it would seem to place some limits on the permissible chit-chat. Also: no encryption.

nomel 5y ago

Why is this downvoted? The purpose and limitations of RF bandwidth allocation isn’t exactly widely known.

h2odragon 5y ago
Truly. I have philosophical problems with the existence of the FCC but there's a great deal of interesting and educational discussion to be had here. At the risk of delving further into conspiracy theory I suspect that may be a reason its downvoted; because there's room for debate. There's currently a lot of feeling that once the government is involved debate must be silenced.
- geofft 5y ago
  I didn't downvote it, but I strongly suspect it was because of the sarcasm, the meta-sarcasm, and ultimately the unwillingness to believe that interesting opposing arguments might exist. That is, the post didn't encourage interesting and educational discussion, just derision. The merit of the resulting conversation was despite the initial post, not because of it.

VLM 5y ago

Fcc part 97.101 "General Standards" (d): "No amateur operator shall willfully or maliciously interfere with or cause interference to any radio communication or signal." Pitiful we have to encode "the golden rule" of treat others like you'd have them treat you into law, but here we are its in the CFR. As of 2021 no one has a technological answer to how to avoid various wide band digital technologies from interference against, well, absolutely everything else currently in use, without forcing everyone to operate in a channelized system with massive international coordination problems. The international part is a nightmare, what if, I donno, Bulgaria refuses to channelize? Nothing will work for anyone unless everyone cooperates. Wideband digital modes do NOT play well with others. There are channelized bands around 5 mhz (in the usa) and the FCC does relax quite a bit on wide open microwave bands, but people are going to request turning all of 20 meters into one single user digital channel, and to hell with everyone else currently using the band, apparently into infinity. Its an eternal meme. I guess the best analogy I can come up with, is you can zone land as a public park for people to picnic, but that doesn't mean the land is completely lawless, if you blast your music at 160 dB the police will arrest you for preventing everyone else from enjoying their picnic. We easily right now have the technological ability to turn the 20M band into a single channel, single user, very high speed digital path at 1500 watts. But that's a terrible idea, given the zillions of current users, local and international, who would be kicked off completely unable to operate.