0x0000 wrote:
> I think the bandwidth limitation differs by frequency band - e.g. I can
> remember when I was [very] young hearing satellite telemetry on
> shortwave radio - I'm not sure how that relates to packet radio
> networking, but it does mean to me that some fairly substantial
> bandwidth is available at some frequencies...
Sounds probable, but I need some test equipment to be sure. We need to
find someone to donate us an old Yaesu transceiver :-D
> I know also that there are a number of HAMs doing WiFi and [almost
> certainly] doing packet <-> WiFi and packet <-> wired TCP/IP bridging.
> I ran across some guys doing that when I was in Michigan a few years
> ago, but I don't have the URLs handy.
There are alot of them, because the frequencies a HAM license allows
you to operate in overlap with the 802.11 frequencies, and they allow
you to have a LOT more power. So while it's (again) probably only
marginally legal, a HAM operator could take an existing 802.11 network
and basically shove a steroid up its ass.
> I think the main requirement for setting something like that up would
> be that we have a licensed HAM operator to oversee the equipment - as I
> understand it [keep in mind that my knowledge of HAM is quite dated]
> "shortwave" frequency transmitters require FCC licensed operators.
The license would depend on the equipment used and how dodgy you wanted
to be legally. The cleanest, most legal way to do it is definitely with
some 2 meter equipment and a FCC license to operate (which is not cheap
but not incredibly expensive at around $80, iirc).
> There is also [iirc] a requirement that the radio data transmissions be
> very short duration, hence the "burst" or "packet" terminology.
I haven't heard about that. One would think that if that were the case,
there wouldn't be any reason for the TCP/IP over AX25 support in linux
... ? TCP/IP connections are always ack'ing back and forth, even when
they appear idle.
I don't know, I'm just guessing by the popularity of using it for such
a purpose. I haven't read anything about it being burst either.
> I have also heard that it is legal to send data across the citizens
> band (CB) frequencies provided that the transmissions are short bursts
> - for some reason "9 seconds" sticks in my mind as the allowed
> transmission length, but on the other hand, I might just be making this
> up from random neuron firings in my fevered brain... I should probably
> look it up.
I just got done looking that up, and it appears that whether data is
legal or not is irrelevant; you can't hold a channel up for more than 5
minutes with a "conversation", and you have to wait one minute before
starting another "conversation". So in order to make CB a viable option,
the CBs would have to be controlled via PC. When the 5 minute barrier
was hit, the PCs on both ends would have to roll through channels until
they found a channel (which was != the last channel) which had dead air
on it (breaking up CB conversations with data bursts is NOT a good way
to make friends). Then they'd start handshaking on the new channel and
continue any transmissions interrupted. That's great until we consider
that you might be faced with a condition where the network would be
rolling channels for as long as a minute or two looking for a clear
channel. It's EXTREMELY unlikely that this would happen, given CB's
moderate popularity these days, but it's certainly possible.
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