On Aug 2, 2005, at 12:40 AM, WA4OSH wrote:
Jim,
Ham radio regulations (Part 97) differ quite a bit from unlicensed
regulations (Part 15)...
Jim Thompson wrote:
<snip>
a) explain how they knocked the side lobes down so they didn't have
unwanted emissions outside the band. Your answer here very likely
has the word "filter" in it, but then I'll just ask you for the
mfg/model # of same, so I can verify its claimed performance.
Under part 97.305, amateur radio stations are allowed to use spread
spectrum in the 13cm band 2390-2450 MHz.
Understood (Kd5FGA, btw).
The signal has to be 802.11b, not 802.11g encoded (OFDM is not
Spread Spectrum).
Yeah, but to be pedantic, it could be 802.11 DSSS as well. (802.11b
requires CCK modulation.)
Amateurs are allowed to use up to 1 watt without automatic power
control and up to
100 watts with APC.
Yep.
There is NO limit on antenna gain.
As long as you don't emit signals outside the band above the (strict
in this case) established limits.
The ARRL bandplan is a suggestion, not an FCC requirement.
this is a true statement, but seems to walk over the FCC requirements
as well. Amateur operators can't transmit anywhere
they wish.
Amateurs can operate on channels 1-6 using part 15 equipment.
Yep
Typically hams use channel 5 or 2432 MHz as a center frequency to
avoid
interfering with amateur satellite transmissions near channel 1 or
2400-2410 Mhz. Furthermore, by picking channel 5, you have 18 Mhz
above and 42 Mhz below center frequency for the +/- 11 Mhz signal to
fall into. Part 97.307 describes the spurious emissions requirements.
Right, and have you looked at the sin(x)/x characteristics of the
signal? Have you looked at the band edge
performance plots available in the FCC filings for this card?
Remember that the band edge limits are strict limits (even for
HAMs). This is where the huge antenna gain will get you in trouble.
From what I can tell, their setup could have met these requirements.
Unlikely without some fairly big channel (or band) filters.
b) explain how they transmitted their HAM call sign (perhaps they set
the ESSID to it, but this wouldn't fulfill the requirements of
Part 97)
Amateur stations using 802.11b must identify every 10 minutes
according
to Part 97.119 b(3). ASCII is a recognized code. Setting the SSID to
callsign1-callsign2 in the peer-to-peer mode is enough for ID.
However, it is also acceptable to send identification in the text of
the message, so that anyone with a normal 802.11b card can read the
identities of the transmitting stations. I believe that if they
followed either of these methods, their setup would have met the regs.
Yeah, OK. Are *they* going to explain?
c) send along the call sign(s) used during this experiment, so the
FCC can pull their tickets.
Please tell me where you think they broke any regulations?
any number of potentials exist. To be perfectly blunt, I think the
"we operated under part 97" was a dodge.
Their setup seems to use the minimum required power required to
maintain the link.
I think I showed that the EIRP was at least 25dB over the 11Mbps
sensitivity level. Thats a *BUNCH* of fade margin.
The high gain dishes minimize interference with others using the
same band.
Its unlikely there were any other users in the line of sight. I
accept that.
But out of curiosity, I too would like to know their callsigns and
would be interested in knowing if they met the part 97 logging rule of
their contact.
<snip>
They deemed it reliable because they wanted to. Did they put any
load on the network? Many people will misinterpret the results,
and clamor for 125 mile links with no other requirements than "line
of sight" and "big ears". For the reasons I've shown, and others,
while you might be able to "show" this in a "demo", its both illegal,
and it doesn't (nee: can't) work correctly.
Give these guys a break. These guys are hackers. Who says it has
to be stock software. They should have been able to hack the retry
timer value in the firmware.
Nope. About all you can do is change the number of retries on that f/w.
For a valid contact on ham radio, they have to exchange callsigns
and a
signal report. There is no requirement to have a network load to make
a contact.
This is a complete red herring.
