3 ms·

> High data rate requires line of sight This isnt true. High data rate requires large channel size, which is certainly more commonly found in >1GHz portions of

by ac29 7y ago

> High data rate requires line of sight This isnt true. High data rate requires large channel size, which is certainly more commonly found in >1GHz portions of radio spectrum that require line of sight. But, a 10MHz channel is just as fast at 400MHz as it is a 4GHz. HDTV doesnt require line of sight to gets tens of megabits on VHF/UHF channels.

superkuh 7y ago
In what legal jurisdiction can you use a 10 MHz bandwidth channel under <30 MHz (where you actually get ionospheric bounce (sometimes))? And even worse than the answer to that (nowhere) is that in the USA the data rate limit is actually in terms of symbol rate, not bandwidth used, to a mere 300 baud for the bands that have regular non-line of sight propagation.
- ac29 7y ago
  > In what legal jurisdiction can you use a 10 MHz bandwidth channel under <30 MHz (where you actually get ionospheric bounce (sometimes))? I never implied you could? Its certainly possible in VHF/UHF, though (for licencees). > And even worse than the answer to that (nowhere) is that in the USA the data rate limit is actually in terms of symbol rate, not bandwidth used Sure, but those limits only apply for HF and longer-wavelength frequencies. You're welcome to do 256QAM in the microwave range, for example.
  - superkuh 7y ago
    > Its certainly possible in VHF/UHF, though (for licencees). >You're welcome to do 256QAM in the microwave range, for example. Which gets back to line of sight propagation (tropo is not common) and everything I said in my first post. I've tried the home to car omnidirectional link thing on 902-928 MHz. All that matters is line of sight. I tried a 25w bidirectional amp (ham general license) and that didn't help. I tried bringing the ubiquiti transceivers w/broadband hamnet firmware all the way down to QPSK modulation and the narrowest channel I could. I even tried using narrowband 56k telemetry dongles. I customed designed and built my own microstrip based filters for the front ends. The only thing that really helps, and it's not enough, is height above terrain. When I go park my car on the hills outside of town megabits are possible. But the slightest hill or valley losing LOS kills it.

by ac29 7y ago

superkuh 7y ago

In what legal jurisdiction can you use a 10 MHz bandwidth channel under <30 MHz (where you actually get ionospheric bounce (sometimes))? And even worse than the answer to that (nowhere) is that in the USA the data rate limit is actually in terms of symbol rate, not bandwidth used, to a mere 300 baud for the bands that have regular non-line of sight propagation.

ac29 7y ago
> In what legal jurisdiction can you use a 10 MHz bandwidth channel under <30 MHz (where you actually get ionospheric bounce (sometimes))? I never implied you could? Its certainly possible in VHF/UHF, though (for licencees). > And even worse than the answer to that (nowhere) is that in the USA the data rate limit is actually in terms of symbol rate, not bandwidth used Sure, but those limits only apply for HF and longer-wavelength frequencies. You're welcome to do 256QAM in the microwave range, for example.
- superkuh 7y ago
  > Its certainly possible in VHF/UHF, though (for licencees). >You're welcome to do 256QAM in the microwave range, for example. Which gets back to line of sight propagation (tropo is not common) and everything I said in my first post. I've tried the home to car omnidirectional link thing on 902-928 MHz. All that matters is line of sight. I tried a 25w bidirectional amp (ham general license) and that didn't help. I tried bringing the ubiquiti transceivers w/broadband hamnet firmware all the way down to QPSK modulation and the narrowest channel I could. I even tried using narrowband 56k telemetry dongles. I customed designed and built my own microstrip based filters for the front ends. The only thing that really helps, and it's not enough, is height above terrain. When I go park my car on the hills outside of town megabits are possible. But the slightest hill or valley losing LOS kills it.