[Scan-DC] Fairfax Dispatch - 460.575

[Randy Benn]

Shawn,

Interesting possibilities.

Do you think they would put the SCADA traffic out on the conventional 
dispatch freq.?  Also, even if it were SCADA traffic, I would expect some 
kind of modem-like audio.  When the squelch breaks, it is just silence, like 
someone keying a mic, then not taking.  Also, I don't think it would be 
encrypted traffic, for essentially the same reasoning; even if it were 
encrypted traffic, I would expect to hear something, not a silent carrier.

Randy

----- Original Message ----- 
From: "Shawnerz" <shawnerz at yahoo.com>
To: "Randy Benn" <randybenn at gmail.com>; "scan dc" <scan-dc at mailman.qth.net>
Sent: Monday, July 10, 2006 4:33 PM
Subject: Re: [Scan-DC] Fairfax Dispatch - 460.575


>
> Randy,
> I don't monitor the system, but there are a couple
> possibilities:
> 1.  It could be interference.  For whatever reason,
> the base station "sees" the interference (intermod,
> adjacent channel, whatever) as a valid signal and is
> repeating it.  In the scenario, the system controller
> would show the repeater as busy and it would not be
> availible for use while the interference is active.
> 2.  It could encrypted traffic and you're hearing the
> encrypted output.
> 3.  It's analog SCADA (Station Control And Data
> Automation) traffic.  For example, in Montgomery
> County, they use SCADA units to report water well
> alarms, flow rates and stuff like that.  The units
> have their own talkgroup and the demodulated audio
> resembles static to the untrained ear.
>
> I hope that helps.
> -Shawn
> --- Randy Benn <randybenn at gmail.com> wrote:
>
>> I've recently been monitoring FFX dispatch on their
>> conventional freq. rather than the TRS.  I've
>> noticed a strange behavior in that the squelch will
>> frequently break, but there is no audio that
>> follows.  This has been verified on multiple radios
>> and in multiple locations, so it doesn't seem to be
>> related to interference in any way.  I haven't
>> noticed this behavior on 4A on the TRS, so it seems
>> to be limited to the conventional alerting freq.
>> Anybody know what might be going on?
>>
>> Randy
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>>
>
>
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