Newsgroups: comp.robotics
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From: nagle@netcom.com (John Nagle)
Subject: Re: Looking for low-cost wireless data link
Message-ID: <1993Feb14.053449.19251@netcom.com>
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
References: <C2AyAu.J35@world.std.com> <1li21aINN240@shelley.u.washington.edu>
Date: Sun, 14 Feb 1993 05:34:49 GMT
Lines: 46

>As a ham radio operator, i can tell you that you could use packet radio IF
>your rf output on each transmitter was under I believe 100 mW and you label    
>the thing EXPERIMENTAL.  Corrections on my information are welcome, but I 
>believe those are the current regulations.

      Er, no.  You need to get up to date.  

      There is an "experimental licence" provision, per 47 CFR 5, under which
you can ask the FCC for permission to do something unusual you can't do
under any other class of licence.  I once obtained approval for an
FM TV link for a robot on 1.245GHz via this route.  If you go this route,
you get a very specific authorization, and a call sign resembling a
ham call, but with "XX" in it.  I had "KA2XXF".  Experimental licences
are rare; there are only a few issued per month, and they're only good
for a year or two, although you can ask to renew.  But it's not something
you just do; you have to file a request, which the FCC will check against
their frequency coordination database.  

      A ham licence offers substantially more authority than the FCC is
likely to give you under an experimental licence.  The main reason to go
experimental is if you are operating as a business.

      Low-power operations are far more restricted than they used to be.
There was a time when the FCC didn't care about anything under 100mW.
That's ancient history.  Part 15 low-power devices now require type
approval.  There is a provision for "home built devices" (47 CFR 15.133),
applicable where no more than five copies of a device are built.  But
you still must comply with all the other restrictions on low-power devices.
There are a few bands available for low-power operation under these
rules, and there are strict power and modulation requirements.

      Spread-spectrum devices are allowed in more bands and are allowed
higher power, and thus most newer low-power wireless LANs are
spread-spectrum.  See 47 CFR 15.126 for the regs; see your LAN dealer
for hardware.  One nice feature of this section is that you can send
commercial traffic, you can encrypt, and you have no content restrictions.
So this is useful for business purposes, and is the way to go for any
products.

       If you have a ham licence (or want to get one), the way to go for
low-bandwidth stuff is probably some TNC-based system.  If your robot has
enough space and power, just put in a wireless LAN card and go with that.
I wouldn't bother with schemes like modifying wireless telephones or
R/C gear any more, although both have been made to work, sort of.

					John Nagle
