RE: The TV That Sent Out a Cry for Help, via Satellite

Mon, 01 Nov 2004 11:58:41 -0400 

This is a multi-part message in MIME format.

I saw this bit of news cross my desk a couple of weeks ago.  I think
Paul Harvey reported it as well.  At first I thought it was rather funny
but after further consideration I realized this was something that can
happen to us all.  So, I decided to check into 121.5MHz distress signal.
As I expected it is an analog signal but it has a very specific
modulation.  The new digital signal system should help considerably and
inadvertent transmissions like this may only be interference.

But my question is how a TV was able to produce the specific modulation
required for a distress signal.

Here are the specs: of the 121.5 MHz beacon

RF Signal Transmitted
        Power: 50 - 100 mW PERP
        Transmission life: 48 hours
        Frequency: 121.5 MHz +/- 6 kHz
        Polarization: Linear

Modulation
        Sweep rate: 2 - 4 Hz
        Range: 300-1600 Hz (swept at least 700 Hz)
        Modulation type: AM
        Modulation depth: > 85%
        Duty Cycle: 40%

Source: http://www.cospas-sarsat.org/Beacons/121Bcns.htm

My suspicion is that the Air Force considers any emission at that
frequency as a possible distress, given the fact that a crash can also
damage a transmitter.

Does anyone know what is SOP in a situation where a transmitter is
simply emitting a CW signal on that frequency?

Oh, and by the way, who would be the governing authority to assess the
$10,000 daily fine?


Regards to all and may your favorite candidate win the election,

-doug


From: [email protected]
[mailto:[email protected]] On Behalf Of David Heald
Sent: Monday, November 01, 2004 7:41 AM
To: [email protected]
Subject: The TV That Sent Out a Cry for Help, via Satellite

Fresh from today's New York Times - our favorite Oregonian emergency
locator tv...  :)

The TV That Sent Out a Cry for Help, via Satellite
By TOM ZELLER Jr.
Pizza ovens, jumbo score boards, Christmas lights and other
appliances have issued emergency distress signals and
brought search and rescue teams running.

http://www.nytimes.com/2004/11/01/technology/01signal.html?th


Have a great week,
-Dave





David Heald
EMC Engineer / Worldwide Regulatory
Symbol Technologies
tel: +1.631.738.5373
fax: +1.631.738.3915

Symbol.  The Enterprise Mobility Company. (TM)


________________________________________________________________________
This email has been scanned for computer viruses.


This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list.    Website:  http://www.ieee-pses.org/

To post a message to the list, send your e-mail to [email protected]

Instructions:  http://listserv.ieee.org/listserv/request/user-guide.html

List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:

     Ron Pickard:              [email protected]
     Scott Douglas             [email protected]

For policy questions, send mail to:

     Richard Nute:           [email protected]
     Jim Bacher:             [email protected]

All emc-pstc postings are archived and searchable on the web at:

    http://www.ieeecommunities.org/emc-pstc




This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list.    Website:  http://www.ieee-pses.org/

To post a message to the list, send your e-mail to [email protected]

Instructions:  http://listserv.ieee.org/listserv/request/user-guide.html

List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:

     Ron Pickard:              [email protected]
     Scott Douglas             [email protected]

For policy questions, send mail to:

     Richard Nute:           [email protected]
     Jim Bacher:             [email protected]

All emc-pstc postings are archived and searchable on the web at:

    http://www.ieeecommunities.org/emc-pstc
Title: RE: The TV That Sent Out a Cry for Help, via Satellite

I saw this bit of news cross my desk a couple of weeks ago.  I think
Paul Harvey reported it as well.  At first I thought it was rather funny
but after further consideration I realized this was something that can
happen to us all.  So, I decided to check into 121.5MHz distress signal.
As I expected it is an analog signal but it has a very specific
modulation.  The new digital signal system should help considerably and
inadvertent transmissions like this may only be interference.

But my question is how a TV was able to produce the specific modulation
required for a distress signal.

Here are the specs: of the 121.5 MHz beacon

RF Signal Transmitted
        Power: 50 - 100 mW PERP
        Transmission life: 48 hours
        Frequency: 121.5 MHz +/- 6 kHz
        Polarization: Linear

Modulation
        Sweep rate: 2 - 4 Hz
        Range: 300-1600 Hz (swept at least 700 Hz)
        Modulation type: AM
        Modulation depth: > 85%
        Duty Cycle: 40%

Source: http://www.cospas-sarsat.org/Beacons/121Bcns.htm

My suspicion is that the Air Force considers any emission at that
frequency as a possible distress, given the fact that a crash can also
damage a transmitter.

Does anyone know what is SOP in a situation where a transmitter is
simply emitting a CW signal on that frequency?

Oh, and by the way, who would be the governing authority to assess the
$10,000 daily fine?


Regards to all and may your favorite candidate win the election,

-doug

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of David Heald
Sent: Monday, November 01, 2004 7:41 AM
To: [email protected]
Subject: The TV That Sent Out a Cry for Help, via Satellite

Fresh from today's New York Times - our favorite Oregonian emergency
locator tv...  :)

The TV That Sent Out a Cry for Help, via Satellite
By TOM ZELLER Jr.
Pizza ovens, jumbo score boards, Christmas lights and other
appliances have issued emergency distress signals and
brought search and rescue teams running.

http://www.nytimes.com/2004/11/01/technology/01signal.html?th


Have a great week,
-Dave





David Heald
EMC Engineer / Worldwide Regulatory
Symbol Technologies
tel: +1.631.738.5373
fax: +1.631.738.3915

Symbol.  The Enterprise Mobility Company. (TM)


________________________________________________________________________
This email has been scanned for computer viruses.

----------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list.    Website:  http://www.ieee-pses.org/

To post a message to the list, send your e-mail to [email protected]

Instructions:  http://listserv.ieee.org/listserv/request/user-guide.html

List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:

     Ron Pickard:              [email protected]
     Scott Douglas             [email protected]

For policy questions, send mail to:

     Richard Nute:           [email protected]
     Jim Bacher:             [email protected]

All emc-pstc postings are archived and searchable on the web at:

    http://www.ieeecommunities.org/emc-pstc



----------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list.    Website:  http://www.ieee-pses.org/

To post a message to the list, send your e-mail to [email protected]

Instructions:  http://listserv.ieee.org/listserv/request/user-guide.html

List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:

     Ron Pickard:              [email protected]
     Scott Douglas             [email protected]

For policy questions, send mail to:

     Richard Nute:           [email protected]
     Jim Bacher:             [email protected]

All emc-pstc postings are archived and searchable on the web at:

    http://www.ieeecommunities.org/emc-pstc

Attachment: ATT18318.txt
Description: Binary data

Reply via email to