[RFI] ROTHR Interference?

Paul Christensen w9ac at arrl.net
Tue Sep 30 15:10:15 EDT 2014


Many thanks for confirming.  I'm a bit surprised it's heard as far north as 
VE6.  Here in FL, it's pretty damn bad.  Later this week, I'll place a call 
into Raytheon's ROTHR division.  They probably won’t offer up much 
information but it's a try.

Paul, W9AC

-----Original Message----- 
From: Don Moman VE6JY
Sent: Tuesday, September 30, 2014 3:02 PM
To: Rfi at contesting.com
Subject: Re: [RFI] ROTHR Interference?

I hear it on 80m, often covers from  ~3.3 to 3.750 in one chunk before it
moves on...  Noticed it last winter/spring but it seems to be more regular
now and a bit stronger.

I must comment on your QRZ page - very nicely done.  That's what a QRZ page
should be .....

73 Don

On Tue, Sep 30, 2014 at 11:50 AM, Paul Christensen <w9ac at arrl.net> wrote:

> For the past month, I've been plagued with a "chopping" interference
> between 80m-30m.  The interference is not local, it's ionospheric.  This 
> is
> not a form of interference you find by getting out and searching the
> neighborhood.
> Ops from Florida are hearing this and I hear it being discussed on the
> 80m/40m nets.  it started about three months ago.  It has the same level 
> as
> the Department of Homeland Security's ROTHR system that detects illicit
> controlled-substance traffic in the Caribbean by triangulating pings from
> three high-power ROTHR systems located in Texas, VA, and PR.  I have not
> heard the usual ROTHR sweeps during this time.  This new form of sweep may
> have taken the place of the older ping that sweeps at a rate of 100
> kHz/sec. That sweep sounded like someone transmitting a carrier and
> spinning the VFO knob at a constant rate.  The new sweep has a fast
> chopping component as well as fast pulses within each sweep.  This lasts
> for a bit over 2 minutes and repeats at different parts of the spectrum
> between 3-10 MHz.   If any of you recall the "Russian Woodpecker," it 
> sound
> much like that system only with faster pulses.
> Like the DHS ROTHR, it's us folk in Florida that get the brunt of it.  If
> you operate outside of the southeast U.S., you may not even hear it.
> https://www.txarmymars.org/downloads/RaytheonRadarOverTheHorizon.pdf
> I have attached a photo of the sweep at the opening of my QRZ.com page.
> http://www.qrz.com/db/W9AC
> Anyone know for sure if DHS changed the sweep pattern?
> Paul, W9AC
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