Reply-To: ornitz@kodak.com
From: Barry Ornitz <ornitz@kodak.kodak.com>
Subject: Re: Apple Wants Radio Waves For Data Transmission
Organization: Eastman Kodak Co, Rochester, NY
Date: Fri, 22 Feb 91 00:07:59 GMT

In article <telecom11.140.2@eecs.nwu.edu> Rolf Meier <mitel!Software!
meier@uunet.uu.net> writes:

> In article <telecom11.119.8@eecs.nwu.edu> Alan Ruffer <alan@
> adept.uucp> writes:

>> The REALLY sad part about all this is that 902.0 - 928.0 Mhz is the
>> amateur radio 33 centimeter band.  Devices that operate in this band
>> are NOT guaranteed freedom from interference!  There are other
>> wireless gadgets that operate in this frequency range too.  Buyers of
>> these devices should be aware of this.  While it is illegal for an
>> amateur to intentionally interfere, these devices are subject to
>> unintentional interference, and amateurs may ALSO be subject to
>> interference from these transmiters.

Legal operation by amateurs can cause interference to these systems.
Likewise amateurs can have these systems shut down if they cause
interference to the amateurs.

> In theory, narrowband transmissions in the 902-928 band should not
> cause interference to spread spectrum transmissions in that band, and
> vice versa.  That is the whole purpose of allowing spread spectrum to
> operate in that band.

Unfortunately, many manufacturers have skimped on their designs and
narrow band transmissions can cause significant interference.

> Now, any band is subject to interference from transmissions which
> operate illegally within that band, but that is a matter of
> enforcement, not regulation.

> There are a number of spread spectrum systems operating successfully
> in the ISM (industrial, scientific, medical) bands, such as 902-928.
> According to my chart of spectrum allocations, this is a "secondary"
> amateur band, whatever that means.  I don't believe it is encouraged
> for amateur usage.

The 902 to 928 MHz Amateur Radio band is licensed for use in ITU
Region 2 on a secondary basis.  This basically means that hams must
not cause harmful interference to stations in the Government
Radiolocation Service and they are not protected from interference
from the same.  There are also some special limitations in areas of
Colorado, Wyoming, Texas, and New Mexico.  Amateurs are not protected
by ISM devices operating on these bands either.

However, radio modems are not ISM devices (these are usually
dielectric heaters, diathermy equipment, industrial microwave ovens,
etc.).  The spread spectrum devices recently allowed by the FCC on
this band are Part 15 devices.  According to the FCC, they must be
operated on a non-interference basis to any licensed users of this
band including amateurs.  This means that they may not cause harmful
interference to licensed operations and they must accept any
interference that these systems may cause to their own operations.

Some of the current spread spectrum devices for this band have virtually no
tolerance for interference, and often a narrowband amateur transmission can
completely lock up their system.  Once again the FCC has demonstrated their
lack of technical expertise in spectrum planning!  :-(

Finally, use of the 902 MHz band by amateurs is not discouraged.  It
is gaining popularity with amateurs for digital networking by packet
radio.


Barry L. Ornitz   ornitz@kodak.com