[Scan-DC] Metro: DC Fire and EMS radio encryption blamed for failure in de - DC News FOX 5 DC WTTG

[Luke Berndt]

When DCFD switched to their new P25 System they also added a lot of
channels in the 700MHz band. I wonder if some of those frequencies were not
added into the repeater?

On Fri, Jan 23, 2015 at 1:49 PM, Jeff Krauss <jeff at krauss.ws> wrote:

> From what I know of Distributed Antenna Systems like those used in the
> Metro tunnels, they do not touch the encrypted digital voice in the
> baseband data stream.
>
> A DAS consists of one or more indoor transceivers with antennas that are
> connected (often by fiber) to an outdoor transceiver and antenna.
>
> The handheld Fire Department radio transmits on the assigned frequency,
> that transmission is received by the indoor antenna in the tunnel,
> demodulated by the indoor receiver to a baseband data stream, and
> upconverted by the fiber transmitter to a light frequency for transmission
> over fiber to an outdoor transmitter and antenna.
>
> The fiber receiver converts the light back to baseband data which is then
> sent to an outdoor transmitter that modulates the data stream on the same
> assigned frequency and transmits it to the Fire Department base station.
>
> The process simply repeats the encrypted voice data stream without any
> need to decrypt it.
>
> It's conceivable that a poorly-engineered DAS could have filters that
> introduce enough distortion so that data errors are introduced into the
> encrypted voice data stream.  Enough errors might affect decryption, but
> would probably have also affected rendering of unencrypted digital voice
> before the Fire Department started encrypting, and so would have been
> corrected then.
>
> Jeff
>
>
>
>
>
> At 12:16 AM 1/23/2015, Dewey3 wrote:
>
>> I would respectfully disagree.  Antennas must be connected to "something"
>> to work.  Just running "leaky" coax through the tunnels will not do
>> anything if that coax is not connected to something to assist with/boost
>> the received signal.  That something, if not encryption capable, is not
>> going to carry/repeat an encrypted signal.  The only place where this
>> would
>> be a non-factor is with direct/simplex transmissions.  I know there were
>> reports that the direct channels were not working (insert rhetorical why),
>> but outside of those direct channels, encryption could have very much
>> played a role.
>>
>> Dewey
>> On Jan 22, 2015 11:04 PM, "Jeff Krauss" <jeff at krauss.ws> wrote:
>>
>> > Everyone should read Dave Statter's commentary and Dallas Lipp's comment
>> > on Dave Statter's page.
>> > http://www.statter911.com/2015/01/22/attention-members-
>> > congress-reporters-metro-not-talk-dc-fire-radios-dcfd-
>> > doesnt-talk-metros-radios/
>> > Encryption may have created a problem for the public safety radio base
>> > station located at the Metro ops communications center (OCC) in
>> Landover,
>> > but probably not for the distributed antenna system within Metro
>> tunnels.
>> > Encryption (although we hate it) probably had no impact on the incident.
>> > Sorry.
>> >
>> >
>> > At 10:46 PM 1/22/2015, Alan Henney wrote:
>> >
>> >  Metro: DC Fire and EMS radio encryption blamed for failure in de - DC
>> >> News FOX 5 DC WTTG
>> >>
>> >> http://tinyurl.com/muoxjjk
>> >> ______________________________________________________________
>> >> Scan-DC mailing list
>> >> Home: http://mailman.qth.net/mailman/listinfo/scan-dc
>> >> Help: http://mailman.qth.net/mmfaq.htm
>> >> Post: mailto:Scan-DC at mailman.qth.net
>> >>
>> >> This list hosted by: http://www.qsl.net
>> >> Please help support this email list: http://www.qsl.net/donate.html
>> >>
>> >
>> > ______________________________________________________________
>> > Scan-DC mailing list
>> > Home: http://mailman.qth.net/mailman/listinfo/scan-dc
>> > Help: http://mailman.qth.net/mmfaq.htm
>> > Post: mailto:Scan-DC at mailman.qth.net
>> >
>> > This list hosted by: http://www.qsl.net
>> > Please help support this email list: http://www.qsl.net/donate.html
>> >
>> ______________________________________________________________
>> Scan-DC mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/scan-dc
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Scan-DC at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
> ______________________________________________________________
> Scan-DC mailing list
> Home: http://mailman.qth.net/mailman/listinfo/scan-dc
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Scan-DC at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>