Emergency Messaging And AM
 

Crossposted to:

rec.radio.amateur.antenna,rec.radio.amateur.misc,r ec,radio.amateur.equipment

Novitiate he

I am learning AM broadcast basics in particular the issues regarding the
geo-targeted broadcasting of alert messages from moving vehicles. Would
most appreciate any assistance.

Due to Katrina/Rita, the company I work for has been given the opportunity
to demonstrate a messaging system that would reach out approximately 1 mile
+/- in transmission deliverance. This would be an "overbroadcast" (my term)
in that it would override local AM radio broadcasting to reach into cars,
trucks etc. In particular, we are working with a stationary site (a
chemical spill for instance) and an emergency vehicle that would move back
and forth at and through the site, at up to 70 mph, broadcasting an alert,
voice and tone message.

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

All comments appreciated.
--
Drop the alphabet for email

"Ari Silversteinn" wrote in message
...
Crossposted to:

rec.radio.amateur.antenna,rec.radio.amateur.misc,r ec,radio.amateur.equipment

Novitiate he

I am learning AM broadcast basics in particular the issues regarding the
geo-targeted broadcasting of alert messages from moving vehicles. Would
most appreciate any assistance.

Due to Katrina/Rita, the company I work for has been given the opportunity
to demonstrate a messaging system that would reach out approximately 1
mile
+/- in transmission deliverance. This would be an "overbroadcast" (my
term)
in that it would override local AM radio broadcasting to reach into cars,
trucks etc. In particular, we are working with a stationary site (a
chemical spill for instance) and an emergency vehicle that would move back
and forth at and through the site, at up to 70 mph, broadcasting an alert,
voice and tone message.

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna
mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

All comments appreciated.
--
The things that pop into my mind are why AM rather than FM, which tends to
be more local, and do you intend to 'over-broadcast' only the local channels
(how many?) - I assume you intend to make the channel(s) selectable - or the
entire band to ensure you get everyone? Assuming that there is a commercial
AM broadcast station in the vicinity (what, 10 miles? 20 miles?) you are
probably going to be flat out getting a mobile rig to ride over it. How do
you intend to do this?

Cheers.

Ken

A disadvantage I see is that a waiver is going to be required in order
not to violate FCC rules. In fact, in the state of Florida, interfering
with broadcast stations is against state law, so another hurdle to be
overcome. That being said, for this system to work, you have to blanket
the entire AM and FM broadcast bands. Even doing so will leave out the
motorists who use XM or Sirius, the Ipod listeners and those who are
driving with their cellphones plugged into their ears.



Ari Silversteinn wrote:

Crossposted to:

rec.radio.amateur.antenna,rec.radio.amateur.misc, rec,radio.amateur.equipment

Novitiate he

I am learning AM broadcast basics in particular the issues regarding the
geo-targeted broadcasting of alert messages from moving vehicles. Would
most appreciate any assistance.

Due to Katrina/Rita, the company I work for has been given the opportunity
to demonstrate a messaging system that would reach out approximately 1 mile
+/- in transmission deliverance. This would be an "overbroadcast" (my term)
in that it would override local AM radio broadcasting to reach into cars,
trucks etc. In particular, we are working with a stationary site (a
chemical spill for instance) and an emergency vehicle that would move back
and forth at and through the site, at up to 70 mph, broadcasting an alert,
voice and tone message.

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

All comments appreciated.



--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.

Hi Ari

I always wonder whether broadcast at the most common IF frequencies
would be a viable alternative? (eg 455khz for AM) Legality issues aside
of course... This would make frequency selection a little easier to
engineer. You wouldnt have to divide your power budget into many
operating frequencies as well. Problem is that you'd need a lot higher
ERP especially since car mounted radios tend to be better shielded than
portables. (You'll need to experiment some)

Since part of your engineering exercise will be to determine what ERP
you want from the system you are proposing, the size of the antenna only
needs to be considered in line with the transmitter output power.
Obviously there will be a useful compromise somewhere that is cost
effective. You might for example want a 100 watt TX for each frequency
with a fairly lossy/terminated and loaded antenna. Your first port of
call will be to determine what the likely highest strength of an AM/FM
broadcast signal you will need to override, add maybe 20dB to that and
work out your needed ERP. You will find lots of texts about the
inefficiencies of MF antennas mounted on motor vehicles so that will
give you some numbers to work with. Remember that making the antenna
wideband will also introduce substantial loss. Note that you cant design
the system to always work as you'll have situations where the radio
stations transmitting antenna is right next to then freeqy where the
event occurred! Decide on some statistical coverage percentage thing etc
etc...

I worked for a concern in Sydney Australia that put in tunnel
rebroadcast systems in the major underground roadworks in Sydney,
Melbourne and Perth. Being in a tunnel of course there werent really any
licensing issues. The system consisted of not only broadcast band (AM &
FM) receivers but spot VHF/UHF FM receivers and transmitters for police,
fire etc vehicles. Each broadcast frequency had its own transmitter. It
was thought to be a better idea than using a wide band TX covering all
frequencies. AM broadcast was coupled to a very long wire and the rest
used a terminated leaky coax run.

Cheers Bob W5/VK2YQA

Ari Silversteinn wrote:
I am learning AM broadcast basics in particular the issues regarding the
geo-targeted broadcasting of alert messages from moving vehicles. Would
most appreciate any assistance.

On Sun, 2 Oct 2005 18:29:13 -0400, Ari Silversteinn
wrote:

Crossposted to:

rec.radio.amateur.antenna,rec.radio.amateur.misc, rec,radio.amateur.equipment

Novitiate he

Clearly,

I am learning AM broadcast basics in particular the issues regarding the
geo-targeted broadcasting of alert messages from moving vehicles. Would
most appreciate any assistance.

Nice idea but......

Due to Katrina/Rita, the company I work for has been given the opportunity
to demonstrate a messaging system that would reach out approximately 1 mile
+/- in transmission deliverance. This would be an "overbroadcast" (my term)
in that it would override local AM radio broadcasting to reach into cars,
trucks etc. In particular, we are working with a stationary site (a
chemical spill for instance) and an emergency vehicle that would move back
and forth at and through the site, at up to 70 mph, broadcasting an alert,
voice and tone message.

And what makes you think anyone is going to be listening on AM. I
think the vast majority of radio listenings in urban areas listen to
FM except possibly for drive time shows, 24 hour news stations and the
comparatively few people enamored of talk or religious radio. FM of
course is subject to the capture effect wherein the strongest signal
prevails to the exclusion of others (at least that is the theory).

AM, particularly at night is subject to strong skywaves.

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

I think the problem here is not the technology, but a fundamental
misconception of what it is you are trying to prove and who is likely
to be your audience. At this point you do not need an engineer, you
need a sociologist.

W3JT

All comments appreciated.

I agree Bob. "Tunnel Radio" systems have been around for over 20
years, and AFAIK all broadcast on dual IF frequencies covering both am
and fm car radios. Here in Boston this type of system is in use in all
our tunnels.

Harry C.

Well, Ari, I can tell you this. People used to mock the fact that I had 7
antennas on my 1957 station wagon almost 50 years ago, but these days, the
airwaves are so bereft of anything worth listening to, I never turn on a
radio in the car. So, I will never hear your message no matter what you
try.

Now, having said that, here is how the system design needs to be:
Since the frequency to which a target radio is tuned is an unknown, and
since the input contains a good trap for the IF frequency, your transmitter
needs to radiate about 2 KW ERP at each of three frequencies in the
broadcast band separated by 262 kHz and 455 kHz. This will mix in the front
end and produce a useful IF. Same technique on FM using two frequencies
10.7 MHz apart.

Good luck on the AM. With expected antenna efficiencies at that wavelength
of about 3%, you are going to need over 100 kW of RF and antenna components
with equivalent power ratings.

Let us know how it works out. The place I used to work no bid this about 20
years ago due to these problems, and that was not the first time this crazy
idea surfaced.

--
Crazy George
"Ari Silversteinn" wrote in message
...
Crossposted to:


rec.radio.amateur.antenna,rec.radio.amateur.misc,r ec,radio.amateur.equipment

Novitiate he

I am learning AM broadcast basics in particular the issues regarding the
geo-targeted broadcasting of alert messages from moving vehicles. Would
most appreciate any assistance.

Due to Katrina/Rita, the company I work for has been given the opportunity
to demonstrate a messaging system that would reach out approximately 1
mile
+/- in transmission deliverance. This would be an "overbroadcast" (my
term)
in that it would override local AM radio broadcasting to reach into cars,
trucks etc. In particular, we are working with a stationary site (a
chemical spill for instance) and an emergency vehicle that would move back
and forth at and through the site, at up to 70 mph, broadcasting an alert,
voice and tone message.

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna
mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

All comments appreciated.
--
Drop the alphabet for email

Ari wrote:
"--amessaging system that would reach out approximately 1 mile--."

You don`t need a radio tire truck. You need a SOUND TRUCK with an AIR
HORN to get the audience`s attention to listen to the message.

Best regards, Richard Harrison, KB5WZI

Amen to that Richard.
I also question the wisdom of transmitting RF in a hazardous chemical
spillage area.

GeoffC

"Richard Harrison" wrote in message
...
Ari wrote:
"--amessaging system that would reach out approximately 1 mile--."

You don`t need a radio tire truck. You need a SOUND TRUCK with an AIR
HORN to get the audience`s attention to listen to the message.

Best regards, Richard Harrison, KB5WZI

On Mon, 3 Oct 2005 11:59:58 +1300, Ken Taylor wrote:

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

All comments appreciated.
--
The things that pop into my mind are why AM rather than FM, which tends to
be more local, and do you intend to 'over-broadcast' only the local channels
(how many?) - I assume you intend to make the channel(s) selectable - or the
entire band to ensure you get everyone?

The issue of selective vs full range broadcasting is a matter that has not
been decided either by client, company or possibility. There are plusses
and minus' to each.

Selective would entail less power but we are being told power of the fire
engine is not an issue.

Assuming that there is a commercial
AM broadcast station in the vicinity (what, 10 miles? 20 miles?) you are
probably going to be flat out getting a mobile rig to ride over it. How do
you intend to do this?

Cheers.

Ken

lol Good question, Ken. Any suggestions?
--
Drop the alphabet for email

On Sun, 02 Oct 2005 23:42:16 GMT, **THE-RFI-EMI-GUY** wrote:

A disadvantage I see is that a waiver is going to be required in order
not to violate FCC rules. In fact, in the state of Florida, interfering
with broadcast stations is against state law, so another hurdle to be
overcome.

Yes, the budget is rich with expected legal expenses. Since DHS has become
a player in this, we are hopeful that we can get the necessary punch to
overcome FCC and statutory issues.

That being said, for this system to work, you have to blanket
the entire AM and FM broadcast bands. Even doing so will leave out the
motorists who use XM or Sirius, the Ipod listeners and those who are
driving with their cellphones plugged into their ears.

Do we have to blanket or only blanket each locale, that is, the
broadcasting stations of each locale?

Not only will we miss those no AM/FM listeners, we will miss those that
don't have their radios on. An aggressive, road sign campaign is planned
something like " Turn On Your Radio, It Could Save Your Life" type of thing
near each incident site.

--
Drop the alphabet for email

On Sun, 02 Oct 2005 19:46:56 -0500, Bob Bob wrote:

Hi Ari

Thanks for comments, Bob.

I always wonder whether broadcast at the most common IF frequencies
would be a viable alternative? (eg 455khz for AM) Legality issues aside
of course...

I'm missing your point. Please explain.

This would make frequency selection a little easier to
engineer. You wouldnt have to divide your power budget into many
operating frequencies as well. Problem is that you'd need a lot higher
ERP especially since car mounted radios tend to be better shielded than
portables. (You'll need to experiment some)

Agreed.

Since part of your engineering exercise will be to determine what ERP
you want from the system you are proposing, the size of the antenna only
needs to be considered in line with the transmitter output power.
Obviously there will be a useful compromise somewhere that is cost
effective. You might for example want a 100 watt TX for each frequency
with a fairly lossy/terminated and loaded antenna. Your first port of
call will be to determine what the likely highest strength of an AM/FM
broadcast signal you will need to override, add maybe 20dB to that and
work out your needed ERP.

Good advice here, will 20db do it?

You will find lots of texts about the
inefficiencies of MF antennas mounted on motor vehicles so that will
give you some numbers to work with. Remember that making the antenna
wideband will also introduce substantial loss. Note that you cant design
the system to always work as you'll have situations where the radio
stations transmitting antenna is right next to then freeqy where the
event occurred! Decide on some statistical coverage percentage thing etc
etc...

Yes, we are shooting for max overbroadcasting but the reality is it is a
hit and miss proposition. Even the scenario of geo related obstructions is
a possibility.

I worked for a concern in Sydney Australia that put in tunnel
rebroadcast systems in the major underground roadworks in Sydney,
Melbourne and Perth. Being in a tunnel of course there werent really any
licensing issues.

Is that peculiar to Aus?

The system consisted of not only broadcast band (AM &
FM) receivers but spot VHF/UHF FM receivers and transmitters for police,
fire etc vehicles. Each broadcast frequency had its own transmitter. It
was thought to be a better idea than using a wide band TX covering all
frequencies. AM broadcast was coupled to a very long wire and the rest
used a terminated leaky coax run.

Cheers Bob W5/VK2YQA

Very nice, congrats on that. Was it Yagi technology or fractal?
--
Drop the alphabet for email

On 2 Oct 2005 18:36:56 -0700, wrote:

I agree Bob. "Tunnel Radio" systems have been around for over 20
years, and AFAIK all broadcast on dual IF frequencies covering both am
and fm car radios. Here in Boston this type of system is in use in all
our tunnels.

Harry C.

Harry, is this a "pickup" system for lost signal?
--
Drop the alphabet for email

On Sun, 02 Oct 2005 20:49:50 -0400, J. Teske wrote:

Due to Katrina/Rita, the company I work for has been given the opportunity
to demonstrate a messaging system that would reach out approximately 1 mile
+/- in transmission deliverance. This would be an "overbroadcast" (my term)
in that it would override local AM radio broadcasting to reach into cars,
trucks etc. In particular, we are working with a stationary site (a
chemical spill for instance) and an emergency vehicle that would move back
and forth at and through the site, at up to 70 mph, broadcasting an alert,
voice and tone message.

And what makes you think anyone is going to be listening on AM. I
think the vast majority of radio listenings in urban areas listen to
FM except possibly for drive time shows, 24 hour news stations and the
comparatively few people enamored of talk or religious radio. FM of
course is subject to the capture effect wherein the strongest signal
prevails to the exclusion of others (at least that is the theory).

AM, particularly at night is subject to strong skywaves.

We are making no preference as to AM or FM as in that we will be attempting
to overbroadcast on each. The AM skywave issue is exactly that but the
system need not be perfect, only as perfect as possible.

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

The 3 meter limitation is clearly is a problem here, we haven't modeled a 3
meter yet. I also wonder what, if anything, LFAM gets us in terms of FCC
approvals and state regulations.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

I think the problem here is not the technology, but a fundamental
misconception of what it is you are trying to prove and who is likely
to be your audience. At this point you do not need an engineer, you
need a sociologist.

W3JT

A sociologist?
--
Drop the alphabet for email

On Sun, 2 Oct 2005 22:26:11 -0500, Crazy George wrote:

Well, Ari, I can tell you this. People used to mock the fact that I had 7
antennas on my 1957 station wagon almost 50 years ago, but these days, the
airwaves are so bereft of anything worth listening to, I never turn on a
radio in the car. So, I will never hear your message no matter what you
try.

Not even in an obvious disaster situation?

Now, having said that, here is how the system design needs to be:
Since the frequency to which a target radio is tuned is an unknown, and
since the input contains a good trap for the IF frequency, your transmitter
needs to radiate about 2 KW ERP at each of three frequencies in the
broadcast band separated by 262 kHz and 455 kHz. This will mix in the front
end and produce a useful IF. Same technique on FM using two frequencies
10.7 MHz apart.

Got it, thanks for the specs.

Good luck on the AM. With expected antenna efficiencies at that wavelength
of about 3%, you are going to need over 100 kW of RF and antenna components
with equivalent power ratings.

Yep, at least, maybe more but power availability off the emergency vehicle
is supposed to be a non-issue, we will see.

Let us know how it works out. The place I used to work no bid this about 20
years ago due to these problems, and that was not the first time this crazy
idea surfaced.

Do you think it is crazy from the standpoint of legal or technical. The
system itself would appear to be much needed.
--
Drop the alphabet for email

On Sun, 2 Oct 2005 23:02:15 -0500, Richard Harrison wrote:

Ari wrote:
"--amessaging system that would reach out approximately 1 mile--."

You don`t need a radio tire truck. You need a SOUND TRUCK with an AIR
HORN to get the audience`s attention to listen to the message.

Best regards, Richard Harrison, KB5WZI

I have seen these systems and they have failed to do two things.

Be heard in a modern car with loud radio and great insulation and 2) pass
the populace acceptance test.
--
Drop the alphabet for email

On Mon, 03 Oct 2005 08:22:17 GMT, G L Carter wrote:

Amen to that Richard.
I also question the wisdom of transmitting RF in a hazardous chemical
spillage area.

GeoffC

That is not on our side of the table though. How this sytem is ultimately
used is out of our hands.
--
Drop the alphabet for email

In that case, simply modify the sign to "Tune to 560, it could save your
life" and use a discrete frequency low power transmitter.


"Ari Silversteinn" wrote in message
.. .
On Sun, 02 Oct 2005 23:42:16 GMT, **THE-RFI-EMI-GUY** wrote:

Not only will we miss those no AM/FM listeners, we will miss those that
don't have their radios on. An aggressive, road sign campaign is planned
something like " Turn On Your Radio, It Could Save Your Life" type of
thing
near each incident site.

there is no requirement that anyone listen to any broadcast radio. with the
rapid growth of satellite radio there are even less people listening to
either am of fm broadcast radio. add those who listen to cd's or dvd's and
you get even less.

There are systems that are used for local road emergency notification, the
560khz one comes to mind, something along those lines would be the best bet,
and add in signs on the backs of vehicles. i guess the real question is,
what are you trying to do by overriding local broadcast stations? and over
what size area?


"Ari Silversteinn" wrote in message
...
On Mon, 3 Oct 2005 11:59:58 +1300, Ken Taylor wrote:

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

All comments appreciated.
--
The things that pop into my mind are why AM rather than FM, which tends
to
be more local, and do you intend to 'over-broadcast' only the local
channels
(how many?) - I assume you intend to make the channel(s) selectable - or
the
entire band to ensure you get everyone?

The issue of selective vs full range broadcasting is a matter that has not
been decided either by client, company or possibility. There are plusses
and minus' to each.

Selective would entail less power but we are being told power of the fire
engine is not an issue.

Assuming that there is a commercial
AM broadcast station in the vicinity (what, 10 miles? 20 miles?) you are
probably going to be flat out getting a mobile rig to ride over it. How
do
you intend to do this?

Cheers.

Ken

lol Good question, Ken. Any suggestions?
--
Drop the alphabet for email

On Mon, 3 Oct 2005 11:52:49 -0400, Ari Silversteinn


I think the problem here is not the technology, but a fundamental
misconception of what it is you are trying to prove and who is likely
to be your audience. At this point you do not need an engineer, you
need a sociologist.

W3JT

A sociologist?

Yeah, to figure out what has to be done to get the audience to listen
to you. A psychologist might also work.

Hi Ari

I always wonder whether broadcast at the most common IF frequencies
would be a viable alternative? (eg 455khz for AM) Legality issues aside
of course...


I'm missing your point. Please explain.

I apologise if you already know the following! Its pretty basic radio..

Almost every radio receiver on the market works off the "superhetrodyne"
principal where the incoming signal is mixed with a local oscillator
down to an intermediate frequency. This makes receiver design a little
cheaper as you can then put your expensive filtering at one frequency
rather than have something that has to track the actual transmitted
frequency.

For example a station on the AM band at 870khz is mixed with a local
oscillator of 1325 khz (in the receiver) to get a difference of 455khz.
If the station frequency is changed then one only needs to modify the
local oscillator frequency. This is what the knob on the radio does!

The most common IF frequency for an AM radio happens to be 455khz so
transmitting on that will mean you will be heard on all AM radios in
close proximity. I dont off hand know the most common broadcast FM IF
(maybe 10.7MHz or 7.8Mhz) but that should be easy to find. It is
important to make sure that the IF of the fire trucks FM two-way radio
isnt the same or you'll never be able to hear it inside the truck!

To "broadcast over" you would need to amplitude modulate the AM band
455khz TX and frequency modulate the FM broadcast IF frequency.

Good advice here, will 20db do it?

FM is easier to do than AM. I'd factor in maybe 6dB for FM. You might be
able to get by with 12dB for AM but the original station will make some
small amount of noise under it. The important thing is that the person
listening wil be able to understand the content.

Note that this is of course only relevent when transmitting on the
actual station frequency.

Yes, we are shooting for max overbroadcasting but the reality is it is a
hit and miss proposition. Even the scenario of geo related
obstructions is
a possibility.

Well it shouldnt be that hard to model. Do a AM and FM band coverage
prediction over the freeways etc you are doing the experiment on to
discover what the receive strength will be in dBm. (It doesnt matter
what "gain" you make the RX antenna because it will be the same figure
that is used for your overbroadcast) For every say 200 yard square take
the mean signal of each, then take the 80th percentile as the signal you
have to beat. If that was (say) -80dBm you want -74dBm (for FM) at the
maximum operating distance (was it a mile each way?) You then reverse
model that to determine what the TX EIRP of the thing on the truck has
to be.

There are bound to be contract houses that will do this prediction for
you. I use to work for one that had the software and I have some GPL
versions myself. I cant do MF (ie AM broadcast) though.

Being in a tunnel of course there werent really any
licensing issues.

Is that peculiar to Aus?

The licensing issue or the tunnel? Tunnel rebroadcast is pretty common
around the world. The company I worked for also did one in Indonesia.
Its also used in underground mines.

Very nice, congrats on that. Was it Yagi technology or fractal?

Err, the leaky coax was just a 2km run of an Andrews product that has
leaky holes in the shield. It was fed in the middle with a wide band
splitter and terminated with 50 ohmss at each end. Its quite a common
thing to do in underground environments. (Buildings too) Handy for two
way radio as well as cell phones.

The AM thing was just a very long terminated (600r) wire.

None of the above are yagi or fractal

Cheers Bob


Ari Silversteinn wrote:

On Mon, 3 Oct 2005 11:57:50 -0400, Ari Silversteinn
wrote:
You don`t need a radio tire truck. You need a SOUND TRUCK with an AIR
HORN to get the audience`s attention to listen to the message.
I have seen these systems and they have failed to do two things.
Be heard in a modern car with loud radio and great insulation and 2) pass
the populace acceptance test.

And you've offered this is during an obvious emergency? :
1 Why would they play music loudly in an insulated car when doom is
on their heels?
2 Why would neighbors complain of noise telling them they were about
to be die?

Richard's description adequately suits:
Local - that would reach out approximately 1 mile and "overbroadcast"
to those immediately in danger within a stationary site.

Your objections are more tailored to suit your solution than the
problem.

73's
Richard Clark, KB7QHC

On Mon, 3 Oct 2005 11:28:32 -0400, Ari Silversteinn
wrote:

On Sun, 02 Oct 2005 23:42:16 GMT, **THE-RFI-EMI-GUY** wrote:

A disadvantage I see is that a waiver is going to be required in order
not to violate FCC rules. In fact, in the state of Florida, interfering
with broadcast stations is against state law, so another hurdle to be
overcome.

Yes, the budget is rich with expected legal expenses. Since DHS has become
a player in this, we are hopeful that we can get the necessary punch to
overcome FCC and statutory issues.

That being said, for this system to work, you have to blanket
the entire AM and FM broadcast bands. Even doing so will leave out the
motorists who use XM or Sirius, the Ipod listeners and those who are
driving with their cellphones plugged into their ears.

Do we have to blanket or only blanket each locale, that is, the
broadcasting stations of each locale?

Not only will we miss those no AM/FM listeners, we will miss those that
don't have their radios on. An aggressive, road sign campaign is planned
something like " Turn On Your Radio, It Could Save Your Life" type of thing
near each incident site.

While Florida may have laws to this effect, in fact they are
unenforcable because of federal preemption for all radio matters.
Still illegal, just the wrong enforcement entity. A state or locality
cannot for example legislate on TVI matters (though many have tried.)
When they try, the FCC will send a notice to the locals that they are
in charge and will handle enforcement. Unfortunately the FCC is
unwilling to get involved in the matter of private contracts such as
antenna exclusions in housing developments.

That said, be aware that when it comes to radio useage in the US, the
FCC is actually NOT the ultimate authority. They are responsible only
for those frequencies which a military controlled panel has ceded to
the FCC for administrative purposes. I can't remember the name right
off hand, but during my federal career, I had to work with them and we
actually were able to override an FCC allocation because it interfered
with a military application. While the FCC played ball with the DOD
outfit I worked for, the ultimate beneficiary of that allocation (a TV
station) sued and the matter wound up in Federal Court. The court
reaffirmed the DOD's ultimate sovreignity in this matter. It
ultimately got resolved by some allocation juggling when a combination
of the Court, The FCC and the DOD gave the plaintiff some "religion."

W3JT

On Sun, 2 Oct 2005 18:29:13 -0400, Ari Silversteinn
wrote:

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

Hi Ari,

As you have described it, and have seen the discussion in regard to
the need for ERP - you are so deep in the debit column with AM power
EQUAL to a local broadcaster, that to climb out of that hole would be
prohibitive. READ: no fire truck has a power plant sufficient to
cover both the antenna system losses AND "overbroadcast" as you
desire. And this is for ONE station only. Imagine your broader
mandate to "overbroadcast" all local stations and that hole just gets
deeper.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

With such a plea, to the savvy it reveals you are in over your head.

73's
Richard Clark, KB7QHC

On Mon, 3 Oct 2005 11:28:32 -0400, Ari Silversteinn
wrote:

Yes, the budget is rich with expected legal expenses. Since DHS has become
a player in this, we are hopeful that we can get the necessary punch to
overcome FCC and statutory issues.

Hi Ari,

The various pieces of this jigsaw puzzle is beginning to reveal a
picture here. With the introduction of two governmental
organizations, and their regulations, your "plan" has all the
appearances of being suitably crafted to work on paper. It responds
to the individual issues that any squinty-eyed bureaucrat would demand
be satisfied for his postage sized turf, but in the overall it would
fail miserably, or drive costs so high as to be tainted with the plea
that "aren't people's lives worth the price?"

Let's see, the original spec calls for a disaster situation that is
confined to within 1 mile; that demands the local population be
informed; that over-rides their usual paths of communication; that
reaches them even when they are not engaged in listening.

As already pointed out, big sound trucks do wonders, and have worked
well since the beginning of the last century for this purpose. That
kids inside their home can hear the ice-cream truck a mile away is a
testimony to this simplicity.

Knocking on the door of the local broadcasters and commandeering their
air-time has a time honored tradition of working quite well too. This
involves no more time than getting that expensive mobile power plant
rigged with wide band transmitters working into hugely lossy antenna
systems into the same danger area. After-all, you could as easily
call the first most obvious radio station as them, and you could be
calling the others before they even got on the road.

The solution demanded is that all radio stations respond to a disaster
network alert and citizens tune to the Civil Defense frequency when so
warned by them. Is this another administration cut-back that was
shelved as one of those unnecessary "entitlements?" Have they clipped
all the wires to those old Air Raid sirens? When did the lights go
out in FEMA?

73's
Richard Clark, KB7QHC

On 2005-10-02, Ari Silversteinn wrote:
This would be an "overbroadcast" (my term)
in that it would override local AM radio broadcasting to reach into cars,

My experience with AM (on the aircraft band) is that two transmitters
at the same time yields a horrible squeal and nothing else. The louder
station (usually on the ground with hundreds of watts) has no particular
advantage over the other station (usually in the air with 5-10 watts).
In other words, there is no effect like FM capture.

--
Ben Jackson

http://www.ben.com/

On Mon, 3 Oct 2005 12:01:14 -0400, Fred W4JLE wrote:

In that case, simply modify the sign to "Tune to 560, it could save your
life" and use a discrete frequency low power transmitter.

I assume you mean to take up an unused local channel? Or to bargain for
time on a used one?

Both ideas make sense.
--
Drop the alphabet for email

On Mon, 3 Oct 2005 16:20:40 -0000, Dave wrote:

there is no requirement that anyone listen to any broadcast radio. with the
rapid growth of satellite radio there are even less people listening to
either am of fm broadcast radio. add those who listen to cd's or dvd's and
you get even less.

The loss of listenership is not arguable.

There are systems that are used for local road emergency notification, the
560khz one comes to mind, something along those lines would be the best bet,
and add in signs on the backs of vehicles. i guess the real question is,
what are you trying to do by overriding local broadcast stations?

1) to grab those that are listening to AM/FM, it is still a hyooge market,
2) client request, 3) DHS preference 4) the number of people alerted by a
sign/sticker and independent warning channel is much less than both that
and AM/FM, 5) the possibility that once the AM/FM FCC/NAB bond is broken, a
precedent could be set for cell, sat, threading messaging, etc 6) spinoff
tech for local/reg/national emergencies.

and over
what size area?

1 mile radius max from point of incident, less most probably.
--
Drop the alphabet for email

Do we have to blanket or only blanket each locale, that is, the
broadcasting stations of each locale?

Not only will we miss those no AM/FM listeners, we will miss those that
don't have their radios on. An aggressive, road sign campaign is planned
something like " Turn On Your Radio, It Could Save Your Life" type of thing
near each incident site.

On Mon, 03 Oct 2005 12:58:40 -0400, J. Teske wrote:

While Florida may have laws to this effect, in fact they are
unenforcable because of federal preemption for all radio matters.
Still illegal, just the wrong enforcement entity. A state or locality
cannot for example legislate on TVI matters (though many have tried.)
When they try, the FCC will send a notice to the locals that they are
in charge and will handle enforcement. Unfortunately the FCC is
unwilling to get involved in the matter of private contracts such as
antenna exclusions in housing developments.

Is there a reason that the locals try to overwrite Fed law then?

That said, be aware that when it comes to radio useage in the US, the
FCC is actually NOT the ultimate authority. They are responsible only
for those frequencies which a military controlled panel has ceded to
the FCC for administrative purposes. I can't remember the name right
off hand, but during my federal career, I had to work with them and we
actually were able to override an FCC allocation because it interfered
with a military application. While the FCC played ball with the DOD
outfit I worked for, the ultimate beneficiary of that allocation (a TV
station) sued and the matter wound up in Federal Court. The court
reaffirmed the DOD's ultimate sovreignity in this matter. It
ultimately got resolved by some allocation juggling when a combination
of the Court, The FCC and the DOD gave the plaintiff some "religion."

W3JT

Excellent point, in my research I saw this handoff or spectrum management
authority of the DoD and it makes sense. This is a serious, additional
consideration and is all the more reason to get the DHS' blessings.

Thanks.
--
Drop the alphabet for email

On Mon, 3 Oct 2005 11:28:32 -0400, Ari Silversteinn
wrote:

Yes, the budget is rich with expected legal expenses. Since DHS has become
a player in this, we are hopeful that we can get the necessary punch to
overcome FCC and statutory issues.

On Mon, 03 Oct 2005 10:27:09 -0700, Richard Clark wrote:

Hi Ari,

The various pieces of this jigsaw puzzle is beginning to reveal a
picture here. With the introduction of two governmental
organizations, and their regulations, your "plan" has all the
appearances of being suitably crafted to work on paper. It responds
to the individual issues that any squinty-eyed bureaucrat would demand
be satisfied for his postage sized turf, but in the overall it would
fail miserably, or drive costs so high as to be tainted with the plea
that "aren't people's lives worth the price?"

No one, in the end, will care about that, Richard, it's buzz words. The
economic hooks are in lessened liabilities and coordinating better
emergency evac and site control plans. Money talks here.

Let's see, the original spec calls for a disaster situation that is
confined to within 1 mile; that demands the local population be
informed; that over-rides their usual paths of communication; that
reaches them even when they are not engaged in listening.

As already pointed out, big sound trucks do wonders, and have worked
well since the beginning of the last century for this purpose. That
kids inside their home can hear the ice-cream truck a mile away is a
testimony to this simplicity.

That piece is a given, no argument there, the AM/FM piece is just one more
way to insure commo.

Knocking on the door of the local broadcasters and commandeering their
air-time has a time honored tradition of working quite well too. This
involves no more time than getting that expensive mobile power plant
rigged with wide band transmitters working into hugely lossy antenna
systems into the same danger area. After-all, you could as easily
call the first most obvious radio station as them, and you could be
calling the others before they even got on the road.

Yes, but as we recently saw, things left to the "if come" often don't
"come" ask FEMA. The plan needs to be in place and the control out of the
hands of anyone except local/reg/national authority.

The solution demanded is that all radio stations respond to a disaster
network alert and citizens tune to the Civil Defense frequency when so
warned by them.

Nothing wrong with that if you know where to tune. I don't, come to think
of it.

Is this another administration cut-back that was
shelved as one of those unnecessary "entitlements?" Have they clipped
all the wires to those old Air Raid sirens? When did the lights go
out in FEMA?

73's
Richard Clark, KB7QHC

MOF, it's an idea that came up over dinner during FEMA/NOLA, don't know
about the sirens, all I do know is once FEMA got there, they shutdown most
commo inc police in some cases. They want total control so this p[iece has
more play at the immediate response (local/state) levels.
--
Drop the alphabet for email

Hi Ari

I always wonder whether broadcast at the most common IF frequencies
would be a viable alternative? (eg 455khz for AM) Legality issues aside
of course...


I'm missing your point. Please explain.

On Mon, 03 Oct 2005 11:50:35 -0500, Bob Bob wrote:


I apologise if you already know the following! Its pretty basic radio..

Man, don't apologize, I have this semi-advanced understanding that missed a
lot of the basics, if you get the drift. Thanks.

Almost every radio receiver on the market works off the "superhetrodyne"
principal where the incoming signal is mixed with a local oscillator
down to an intermediate frequency. This makes receiver design a little
cheaper as you can then put your expensive filtering at one frequency
rather than have something that has to track the actual transmitted
frequency.

Got that.

For example a station on the AM band at 870khz is mixed with a local
oscillator of 1325 khz (in the receiver) to get a difference of 455khz.
If the station frequency is changed then one only needs to modify the
local oscillator frequency. This is what the knob on the radio does!

lol ok

The most common IF frequency for an AM radio happens to be 455khz so
transmitting on that will mean you will be heard on all AM radios in
close proximity. I dont know off hand know the most common broadcast FM IF
(maybe 10.7MHz or 7.8Mhz) but that should be easy to find. It is
important to make sure that the IF of the fire trucks FM two-way radio
isnt the same or you'll never be able to hear it inside the truck!

Now this I did not know!

To "broadcast over" you would need to amplitude modulate the AM band
455khz TX and frequency modulate the FM broadcast IF frequency.

Good advice here, will 20db do it?

FM is easier to do than AM. I'd factor in maybe 6dB for FM. You might be
able to get by with 12dB for AM but the original station will make some
small amount of noise under it. The important thing is that the person
listening wil be able to understand the content.

Note that this is of course only relevent when transmitting on the
actual station frequency.

Got it.

Yes, we are shooting for max overbroadcasting but the reality is it is a
hit and miss proposition. Even the scenario of geo related
obstructions is
a possibility.

On Mon, 03 Oct 2005 11:50:35 -0500, Bob Bob wrote:


Well it shouldnt be that hard to model. Do a AM and FM band coverage
prediction over the freeways etc you are doing the experiment on to
discover what the receive strength will be in dBm. (It doesnt matter
what "gain" you make the RX antenna because it will be the same figure
that is used for your overbroadcast) For every say 200 yard square take
the mean signal of each, then take the 80th percentile as the signal you
have to beat. If that was (say) -80dBm you want -74dBm (for FM) at the
maximum operating distance (was it a mile each way?) You then reverse
model that to determine what the TX EIRP of the thing on the truck has
to be.

There are bound to be contract houses that will do this prediction for
you. I use to work for one that had the software and I have some GPL
versions myself. I cant do MF (ie AM broadcast) though.

Found the expertise for that and there is a chunk of open source stuff out
there, freeware.

Being in a tunnel of course there werent really any
licensing issues.

Is that peculiar to Aus?

On Mon, 03 Oct 2005 11:50:35 -0500, Bob Bob wrote:


The licensing issue or the tunnel? Tunnel rebroadcast is pretty common
around the world. The company I worked for also did one in Indonesia.
Its also used in underground mines.

Very nice, congrats on that. Was it Yagi technology or fractal?

Err, the leaky coax was just a 2km run of an Andrews product that has
leaky holes in the shield. It was fed in the middle with a wide band
splitter and terminated with 50 ohmss at each end. Its quite a common
thing to do in underground environments. (Buildings too) Handy for two
way radio as well as cell phones.

The AM thing was just a very long terminated (600r) wire.

None of the above are yagi or fractal

Cheers Bob

Thanks, Bob, I'm all overYagied and underfractalled. lol


--
Drop the alphabet for email

On Mon, 03 Oct 2005 12:44:20 -0400, J. Teske wrote:

On Mon, 3 Oct 2005 11:52:49 -0400, Ari Silversteinn


I think the problem here is not the technology, but a fundamental
misconception of what it is you are trying to prove and who is likely
to be your audience. At this point you do not need an engineer, you
need a sociologist.

W3JT

A sociologist?

Yeah, to figure out what has to be done to get the audience to listen
to you. A psychologist might also work.

Gee, are you trying to hurt my feelings?
--
Drop the alphabet for email

On Mon, 3 Oct 2005 11:57:50 -0400, Ari Silversteinn
wrote:
You don`t need a radio tire truck. You need a SOUND TRUCK with an AIR
HORN to get the audience`s attention to listen to the message.
I have seen these systems and they have failed to do two things.
Be heard in a modern car with loud radio and great insulation and 2) pass
the populace acceptance test.

On Mon, 03 Oct 2005 09:56:25 -0700, Richard Clark wrote:

And you've offered this is during an obvious emergency? :

The acoustic testing has been done, yes, and the PA is obviously intrusive
to the nth degree and is not a panacea for all emergency commo.

1 Why would they play music loudly in an insulated car when doom is
on their heels?

Because they haven't yet been informed, perhaps.

2 Why would neighbors complain of noise telling them they were about
to be die?

It's not always a "death or flee" scenario, it could be hazardous but not
deadly.

Richard's description adequately suits:
Local - that would reach out approximately 1 mile and "overbroadcast"
to those immediately in danger within a stationary site.

Your objections are more tailored to suit your solution than the
problem.

73's
Richard Clark, KB7QHC

I have a client who is much more knowledgeable in these situations than I
am, maybe even you. It's a custom build, not an Ari build.
--
Drop the alphabet for email

On Sun, 2 Oct 2005 18:29:13 -0400, Ari Silversteinn
wrote:

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

On Mon, 03 Oct 2005 10:05:07 -0700, Richard Clark wrote:

Hi Ari,

As you have described it, and have seen the discussion in regard to
the need for ERP - you are so deep in the debit column with AM power
EQUAL to a local broadcaster, that to climb out of that hole would be
prohibitive. READ: no fire truck has a power plant sufficient to
cover both the antenna system losses AND "overbroadcast" as you
desire. And this is for ONE station only. Imagine your broader
mandate to "overbroadcast" all local stations and that hole just gets
deeper.

OK, so we supply the amplification.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

With such a plea, to the savvy it reveals you are in over your head.

73's
Richard Clark, KB7QHC

Doesn't matter if I'm in over my head, the technical side is one I only
need to be able to commo on, there will be others who will be cast with
this task.
--
Drop the alphabet for email

On Mon, 03 Oct 2005 13:37:49 -0500, Ben Jackson wrote:

On 2005-10-02, Ari Silversteinn wrote:
This would be an "overbroadcast" (my term)
in that it would override local AM radio broadcasting to reach into cars,

My experience with AM (on the aircraft band) is that two transmitters
at the same time yields a horrible squeal and nothing else. The louder
station (usually on the ground with hundreds of watts) has no particular
advantage over the other station (usually in the air with 5-10 watts).
In other words, there is no effect like FM capture.

Are you saying that if I am attempting an overbroadcast on, say, 680 AM and
the station is doing the same, and I am 12 db + greater, that all we will
get is squeal?
--
Drop the alphabet for email

Ari Silversteinn wrote:
Are you saying that if I am attempting an overbroadcast on, say, 680 AM and
the station is doing the same, and I am 12 db + greater, that all we will
get is squeal?

One signal is the Beat Frequency Oscillator. I am amazed
that no one has thought of this perfect solution before.

If Morse code were required for all driver's licenses, then
all you have to do is furnish a CW carrier wave. The two
signals would mix and the squeal would be Morse code which
would carry the emergency information.
--
73, Cecil, http://www.qsl.net/w5dxp

On Mon, 03 Oct 2005 20:53:17 GMT, Cecil Moore wrote:

Ari Silversteinn wrote:
Are you saying that if I am attempting an overbroadcast on, say, 680 AM and
the station is doing the same, and I am 12 db + greater, that all we will
get is squeal?

One signal is the Beat Frequency Oscillator. I am amazed
that no one has thought of this perfect solution before.

If Morse code were required for all driver's licenses, then
all you have to do is furnish a CW carrier wave. The two
signals would mix and the squeal would be Morse code which
would carry the emergency information.

What if your fat as a whale and your DL is wedged up your crack in your
back pocket?
--
Drop the alphabet for email

On Mon, 3 Oct 2005 16:33:52 -0400, Ari Silversteinn
wrote:
OK, so we supply the amplification.

OK, this is just a re-run of previous speculations. You don't know
the depth of your energy budget crisis, do you?

Doesn't matter if I'm in over my head, the technical side is one I only
need to be able to commo on, there will be others who will be cast with
this task.

How many leaps of imagination will it take to land on the gravy train?

73's
Richard Clark, KB7QHC

"Ari Silversteinn" wrote in message
...
On Mon, 3 Oct 2005 12:01:14 -0400, Fred W4JLE wrote:

In that case, simply modify the sign to "Tune to 560, it could save your
life" and use a discrete frequency low power transmitter.

I assume you mean to take up an unused local channel? Or to bargain for
time on a used one?

Both ideas make sense.
--
Drop the alphabet for email

if this is for real time notification you don't have time to bargain or to
find an unused channel... and who would listen to you anyway if it was
unused? how often do you turn the knob on your car radio??

what about the emergency broadcast system? that would seem to be the
'proper' method of emergency notification, its already set up for all sorts
of local, regional, and national notifications.

There are a couple of frequiencies for unlicensed low power am stations. You
can see them in use by real estate folks selling houses. There are no
commercial stations on the frequency.

"Ari Silversteinn" wrote in message
...
On Mon, 3 Oct 2005 12:01:14 -0400, Fred W4JLE wrote:

In that case, simply modify the sign to "Tune to 560, it could save your
life" and use a discrete frequency low power transmitter.

I assume you mean to take up an unused local channel? Or to bargain for
time on a used one?

Both ideas make sense.
--
Drop the alphabet for email