There's an article in today's Washington Post

http://preview.tinyurl.com/6ego68

that describes a technology that's under development to provide Internet
access using spectrum in the TV channel range. Apparently this scheme
checks for a signal before it uses a specific frequency and switches to
a different one if it detects that the frequency is in use.

I wonder how this will work and play with amateur radio. I remember
when TV channel 2 was established in my home town, effectively shutting
down six meter ham operation because the TV signal was so weak that even
a correctly-operating six-meter rig would create serious TVI for the
fringe reception of channel 2. Decades have passed and this new
technology surely is much less sensitive to adjacent signals than the
TVs of my childhood, but the analogy persists.

73, Steve KB9X

On Jul 24, 1:41 pm, Steve Bonine wrote:
There's an article in today's Washington Post

http://preview.tinyurl.com/6ego68

that describes a technology that's under development to provide Internet
access using spectrum in the TV channel range. Apparently this scheme
checks for a signal before it uses a specific frequency and switches to
a different one if it detects that the frequency is in use.

I wonder how this will work and play with amateur radio.

Interesting story but a lot of information you need to determine how
much of a problem this would be is missing.

As it sits, the use of "unused" spectrum space in the current TV
broadcast band seems to be a non-issue to us. Seems that they are at
least trying to live within the part 15 rules and are working to
detect when other users pop up on the spectrum and they are working in
a band that will be open for new use in Feb 09. As long as they keep
part 15 power levels, don't try and connect directly to long
unshielded wires hung up high and stay out of the ham radio
allocations what can we say? However if they are demonstrating
something to the FCC, it would seem that they are looking for some
kind of operational waver or rules change. Worth keeping an eye on.

On Thu, 24 Jul 2008 14:41:36 -0400, Steve Bonine wrote:

There's an article in today's Washington Post

http://preview.tinyurl.com/6ego68

that describes a technology that's under development to provide Interne
t
access using spectrum in the TV channel range. Apparently this scheme
checks for a signal before it uses a specific frequency and switches to

a different one if it detects that the frequency is in use.

I wonder how this will work and play with amateur radio. I remember
when TV channel 2 was established in my home town, effectively shutting

down six meter ham operation because the TV signal was so weak that eve
n
a correctly-operating six-meter rig would create serious TVI for the
fringe reception of channel 2. Decades have passed and this new
technology surely is much less sensitive to adjacent signals than the
TVs of my childhood, but the analogy persists.

I'm not too worried about interference to/from amateur radio.

Users aren't going to recognize overload problems as coming from ham gear
..
The things are simply going to intermittently stop operating and they're
going to blame it on an outage of the ISP's base station. It won't play
your voice out their speakers the way it does with an analog TV set. And
they're never going to get FCC approved unless they know how to confine
their emissions to the TV channel they determined was unused. They're no
t
going to spill over into ham bands.

(at least not the legal ones. The illegal ones will spill even if the FC
C
never approves this technology.)

I'm a lot more worried about it as a TV engineer and semi-rural
over-the-air TV viewer. In early tests these things weren't very good at
determining whether a channel was unused. I can see that becoming a big
problem in semi-rural areas like this, where people might be using roofto
p
antennas to get TV but the Internet devices will probably be on makeshift
indoor aerials.

On the other hand, I'm not holding my breath waiting for someone to build
a base station out here. The technology may well never come to places
rural enough to be in TV fringe reception.

On Fri, 25 Jul 2008 05:23:27 -0400, Doug Smith W9WI wrote:
I'm a lot more worried about it as a TV engineer and semi-rural
over-the-air TV viewer. In early tests these things weren't very good
at
determining whether a channel was unused. I can see that becoming a bi
g
problem in semi-rural areas like this, where people might be using roof
to
p
antennas to get TV but the Internet devices will probably be on makeshi
ft
indoor aerials.

(which may end up being the vector by which this stuff bothers ham radio
-- it will interfere with TV reception and the viewers will blame us...)

In article ,
Doug Smith W9WI wrote:

I'm a lot more worried about it as a TV engineer and semi-rural
over-the-air TV viewer. In early tests these things weren't very good at
determining whether a channel was unused. I can see that becoming a big
problem in semi-rural areas like this, where people might be using rooftop
antennas to get TV but the Internet devices will probably be on makeshift
indoor aerials.

According to an article in Moble Radio Technology magazine recently,
there's another issue in some areas (about ten major metro areas)
where various public safety agencies have already been authorized to
use the white space in the channel 14-20 range for various types of
public safety communication.

Some of these applications (e.g. video surveillance cameras) are
designed to be "indetectable" while in operation... which makes things
problematic for the proposed free-white-space-detection devices. The
police would be unamused by having their stakeout-surveillance video
feed stomped upon by web-browsing passersby!

The quick solution to this is to forbid the use of free-white-space
devices in this frequency range, in those cities where public safety
operations have already been authorized. This won't necessarily solve
the problem, if (for example) a user of such a device brings it from a
"wide open" city into a city with restrictions, and doesn't realize
that s/he has to change the device's mode to stay legal.

The pro-audio industry is also up in arms over these whitespace
proposals, as they've been depending for years on Part 15 (or similar)
wireless microphones which operate in the unused TV channel
frequencies. Having to face competition for these frequencies from a
whole bunch of non-coordinated new "find a 'free' frequency and camp
on it" devices could cause problems for them, to say the least!

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Fri, 25 Jul 2008 16:08:32 EDT, (Dave Platt)
wrote:

According to an article in Moble Radio Technology magazine recently,
there's another issue in some areas (about ten major metro areas)
where various public safety agencies have already been authorized to
use the white space in the channel 14-20 range for various types of
public safety communication.

Dave, that's old news, at least 30 years old .It was originally
pushed by the Los Angeles Sheriff's Department which up until that
time had been using VHF low-band (39 MHz) equipment.

The so-called T-Band is almost totally loaded in the major
metropolitan areas authorized for same (See FCC Rules Part 90, Sub
part L). This spectrum is allocated in such a manner as to protect
existing TV stations.

These are one type of systems that our company designs for
public-safety clients. Many agencies are asking the FCC to reassign
unused commercial channels in the T-Band for Public Safety use. We're
in the thick of that. What we are trying to do also is to get the FCC
to expand the radius around the authorized cities as urban growth
moves outward.
--

73 de K2ASP - Phil Kane

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon

e-mail: k2asp [at] arrl [dot] net

On Sat, 26 Jul 2008 02:00:41 -0400, Phil Kane wrote:
These are one type of systems that our company designs for
public-safety clients. Many agencies are asking the FCC to reassign
unused commercial channels in the T-Band for Public Safety use. We're
in the thick of that. What we are trying to do also is to get the FCC
to expand the radius around the authorized cities as urban growth
moves outward.

I think the problem you're going to have (with both of those projects) is
that the compression of the TV band is going to make unused channels in
T-band less common. And especially in the areas outside the existing
radius where you'd like to expand it.

I think the argument you'll get is that 24MHz above channel 51 has alread
y
been set aside for public-safety, should it really need more below channe
l
21?

On Sat, 26 Jul 2008 07:01:43 EDT, Doug Smith W9WI
wrote:

I think the argument you'll get is that 24MHz above channel 51 has already
been set aside for public-safety, should it really need more below channel 21?

Now you have me talking about my business but here I go anyway:

Every petition that we have submitted for our Public Safety clients
who need expansion into non-Public Safety Pool frequencies in T-Band
has been met with what I consider a boiler-plate query from the FCC
that has to be answered formally on the record about whether our
client has considered a 700 MHz system. What we say is this:

1. This is an expansion of existing system which already operates in
T-Band and there are no more Public Safety Pool T-Band channels
available that would not result in harmful interference to another
user of that band.

2. The characteristics of 700 MHz propagation and building
penetration are such that it would require anywhere from five to ten
times as many repeater sites as a T-band system, each one costing
three to five times as much as a T-Band site costs.

3. It is dangerous and unsafe to require a public safety officer
(police or fire) to carry two radios where the possibility exists that
the "wrong" radio would be used in a life-and-death situation.

4. There is no usable 700 MHz equipment on the market at the present
time. Existing 800 MHz equipment is not compatible with the operating
schemes proposed for the 700 MHz band.

5. The systems under consideration are taxpayer funded, and it is
egregious to abandon an existing system and procure a new system just
because the 700 MHz spectrum has been designated for future use. The
taxpayers won't stand for it, even in the name of "homeland security",
the magic words du jour, and obtaining additional sites is a
protracted and expensive procedure in today's environmental-conscious
urban and suburban environment (can you say NIMBY ?).

The documentation to support all the above literally runs into the
thousands of pages - all at the taxpayers' expense.

I'd say more but it would disparage a major manufacturer of equipment.
--

73 de K2ASP - Phil Kane

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon

e-mail: k2asp [at] arrl [dot] net

On Fri, 25 Jul 2008 16:08:32 -0400, Dave Platt wrote:
The quick solution to this is to forbid the use of free-white-space
devices in this frequency range, in those cities where public safety
operations have already been authorized. This won't necessarily solve
the problem, if (for example) a user of such a device brings it from a
"wide open" city into a city with restrictions, and doesn't realize
that s/he has to change the device's mode to stay legal.

They'll probably have to ban them from T-band altogether. But see below.

The pro-audio industry is also up in arms over these whitespace
proposals, as they've been depending for years on Part 15 (or similar)
wireless microphones which operate in the unused TV channel frequencies
..
Having to face competition for these frequencies from a whole bunch of
non-coordinated new "find a 'free' frequency and camp on it" devices
could cause problems for them, to say the least!

One proposal I saw would require wireless-microphone users to transmit a
"beacon" signal at some predetermined location within the TV channel. Th
e
white-space devices would monitor for this beacon.

(both the DTV and analog TV standards essentially already have beacons)

So I suppose you could have the public-safety organizations also transmit
the beacons.

Yes, sometimes I get the impression the pro-audio folks are more upset
about this than the broadcasters.

Doug Smith W9WI wrote:
On Thu, 24 Jul 2008 14:41:36 -0400, Steve Bonine wrote:

There's an article in today's Washington Post

http://preview.tinyurl.com/6ego68

I had to chuckle at the part where she holds the camera on herself at
arms length. High budget reportage.

I also was in awe of the publc safety aspect touted by the one engineer.
First responders, yada yada. Of course they could use it.

The manager who is talking about having a product out in less than a
year, after tehy know what the "rules" are.

Finally the last guy in the red shirt who basically says that what they
have doesn't work.

Golly, if it doesn't have to work, I could have something on the market
in a week or so evil grin


I'm not too worried about interference to/from amateur radio.

This isn't too likely to interfere with Amateur radio. Of course, I
don't think it is too likely to work either. Given the nature of UHF,
the system will have to look at the possible occupation of a frequency
at both the broadcast site and receiver site. Picket fencing can be an
issue. Let's take a look at a potential experience.

The home system (digital signal source) and receiver system (laptop)
look around for a clear space. Say they find one. I am guessing that
there is some sort of Pre-communication going on on some dedicated
frequency. So they find a clear frequency. They start exchanging
packets. Now the laptop moves and a picketed signal shows up, or say the
local church starts it's Saturday evening service. So now the home
system and the receiver system have to search around for a new
frequency. Maybe they find one, and maybe they don't.

Immediate thoughts come to mind:

These systems have to be in some kind of communication to begin with. I
suppose that the laptop could just start transmitting on different
frequencies, hoping to hit the home system, but that would be a long
process.

Talk about a system ripe for interference. There could be a new game in
town, the opposite of Wardriving. If all it takes is another signal on
the same frequency to start a search for a clear one, some social
misfits might just have fun with a sweep generator. Keep the system
hopping, and it will never settle on a frequency.


snippage


I'm a lot more worried about it as a TV engineer and semi-rural
over-the-air TV viewer. In early tests these things weren't very good at
determining whether a channel was unused. I can see that becoming a big
problem in semi-rural areas like this, where people might be using rooftop
antennas to get TV but the Internet devices will probably be on makeshift
indoor aerials.

Is is possible that this is another setup put together by digital
engineers as opposed to RF engineers?

So I agree with Steve that it is likely to be another BPL. This one
might get a little further before failure though, as I think ARRL's
efforts went a long way toward getting BPL marginalized. Obviously we
won't be spending our money on a problem that won't directly affect
Hams. But it has th esame problems, likely interference, lack of
robustness, and probably won't help th epeople touted as the beneficiaries.

Just my .$0.02

- 73 de Mike N3LI -