[Scan-DC] Federal(?) spread spectrum system in 420-450 MHz in the DC area

[Greg Danes]

I think that's exactly it.

https://www.globalsecurity.org/military/systems/ground/eplrs.htm

On Fri, Jan 1, 2021 at 8:40 PM Chris Parris <lists at thefedfiles.com> wrote:

> Hi Andrew,
>
> I suspect that you might be seeing and hearing the Enhanced Position
> Location Reporting System (EPLRS). From the NTIA:
>
> > The military agencies use the band 420-450 MHz for the multi-function
> Position Location Reporting System (PLRS) and the modernized Enhanced
> Position Location Reporting System (EPLRS). EPLRS is a data communications
> network that enables the rapid determination of the locations of all units
> in the network. EPLRS also has communications and navigational capabilities
> in addition to the position location feature. The EPLRS and its airborne
> version, the AEPLRS, are critical to the operations and safety of our
> military forces
>
> It is from this document:
> https://www.ntia.doc.gov/files/ntia/publications/compendium/0420.00-0450.00_01MAR14.pdf
>
> - Chris
>
>
>
> > On Jan 1, 2021, at 9:04 AM, Andrew Clegg <andrew_w_clegg at hotmail.com>
> wrote:
> >
> > For several years, there has been a frequency-hopping spread spectrum
> system operating in the DC area across the entire 420 - 450 MHz band. That
> band is allocated on a primary basis to the federal government for
> radiolocation and on a secondary basis to amateur radio (the "440 band").
> Given the primary allocation status, and the persistence and coverage of
> this system, I presume this is a federal operation of some type. Does
> anyone know what this system is?
> >
> > From my QTH in Arlington, it's fairly strong. If I park my receiver on a
> 440 frequency, the spread spectrum system manifests as constant clicking
> noises as the system rapidly pops in and out of the frequency I'm tuned to.
> It's more noticeable in CW/SSB/AM modes than in FM mode. If I run a
> spectrum analyzer in max hold mode and let it build up for a minute or two,
> there's clearly five 6-MHz wide channels over which the frequencies hop. I
> don't know what the instantaneous bandwidth is; the system hops too fast
> for me to see that.
> >
> > I have heard the system while mobile driving up 95. I start to hear it
> ~20 miles south of the city, and it grows in strength as I get closer to my
> home QTH in Arlington. Other than driving up 95, I have not driven around
> the DC area to see where the signal is max strength.
> >
> > The signals complicate reception of weak signals in the 440 band,
> especially amateur satellite downlinks. I have not noticed any complaints
> from other local hams, but my antennas are in the clear and up high, so I
> may suffer more interference than some other hams do. I'm also not in much
> contact with local ham groups so if they're discussing this topic I may
> have missed it.
> >
> > I'm curious about what the system is and what it's used for. Does anyone
> know where the signal(s) originate from? Who else hears it at their QTH?
> >
> > 73,
> > W4JE
>
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