ANOTHER SIDE of PUBLIC SERVICE—or—Yes Virginia, You can go Transmitter Hunting in the wintertime.

Reg Leister-N3KAS
Pottstown, PA
n3kas@arrl.net
=====================================================================

Despite unseasonably mild temperatures this year, our club’s fox-hunting activities have already wrapped-up
until spring. For some guys already undergoing withdrawal symptoms it was a welcomed call when just a few 
days before Christmas, Lou, N3JKM sent out an email on the Pottstown (PA) Area Amateur Radio Club (PAARC) 
email reflector about a very strong (30 dB+) signal on 151.090 MHz transmitting digital tones. He wanted
to enlist the Transmitter Hunting Team to track down the source of the interference which was not listed
in the FCC Data registry for anywhere in Pennsylvania. His other concern was that a neighboring 
community’s public service radios were licensed on 151.100 MHz and they had all gone silent for obvious 
reasons. He stated that the pulsing noise had been evident for a few weeks and he was copying the noise from 
quite a distance from home on his way to and from work.

Immediately Jim, K3CHJ and Bob, K3DBD took various readings from several locations around Pottstown. In the
meantime, the author noticed from daily travels that a sewer excavation along a local road near Lou’s home
had a pair of mobile traffic lights controlling a single lane of traffic and 3 driveways to an apartment
complex and a cemetery. They were on automatic operation and were radio-controlled as evidenced by a
base-loaded vertical antenna atop their booms.  I immediately suspected them as the culprits and given the
fact that it was now Christmas Eve, was distracted with the impending holiday deadline to finish 2 rocking
chairs and a computer desk for my grandchildren.

These mysterious signals were significantly strong to be copied as far away as 8 miles over rather challenging
terrain. Through triangulation everyone confirmed that yes, the traffic controllers appeared to be the offending
devices. Bob, K3DBD having done extensive digital design work recorded his findings from home on his scope:
“It appears to be some sort of telemetry.  It pulses on for 120 milliseconds every 275 milliseconds.  It is 
Manchester encoded with a preamble at 840 Hz.  I would recognize that anywhere. There is a lot of data between
the preamble and postamble, so whatever it is sending is quite complex.” 

Finally, on Friday morning December 29th, Jim-K3CHJ and I both converged on the site around 7:45 AM. He was armed
with his tracking equipment taking some final measurements and I with my camera. Jim tried to figure out just how
the units were “talking” to each other. It appeared that one was in a “master control mode.”  It did most of the
transmitting and sent data to the other unit about 225 feet away. There were also other sensors mounted on top of
the booms to detect any movement of vehicles in any of 3 driveways that entered the controlled lane of traffic. 

I took several pictures of the site for the club web page and to identify the owners of the equipment. Upon arriving
at home, their website was located and I notified them of the problem that their unlicensed equipment was creating
for the licensed public service radios in the next town, which was also in another county. Despite this being the 
start of a holiday weekend and normally a day off for most businesses, a response was received back from their 
Technical Services Department within a few hours late in the afternoon. 

“We use the SRM6000 Data - Linc radio in conjunction with our portable traffic signals in the US. The radios are 
operated in the 900 MHz band.  In Europe we utilize the 151 MHz band you referenced. I will have our people investigate
the system in Pottstown to ensure the appropriate radio was deployed. If there is a problem it will be corrected
immediately. 

Thank you for bringing this to our attention.”

By the next morning the interference was gone!

Throughout this entire event, the activities and results of our Transmitter Trackers were being posted on our club reflector.
Paul, W3PMK, decided to check a little further on the SRM6000 Data-Linc radios-- [ http://www.data-linc.com/srmfamily/srm6000.htm  ]. 
He learned that they are license-free units operating at 1 watt in the 902-928 MHz ISM (industrial/scientific/medical) band. 
This is the same band (33 cm) that permits amateur use on a secondary basis. These were the radios that were supposed to be in use. 

It is gratifying that our club was able to identify and mitigate this problem as a different kind of public service to our community.
Having interviewed key personnel from the affected municipality, they were at a total loss as to what was causing the problem and more
so, how to resolve it. They had initially enlisted the county’s radio technicians to assist them to no avail. Keep in mind that this
township’s frequency is shared by Public Works, Fire and Police Departments. No one knew what to do. Having it jammed for nearly a
month was a significant communications issue for them. In some cases they were forced to use cell phones which at times were 
impractical from a coverage standpoint. They were quite relieved when I notified their Township Manager and Chief of Police that
our club had identified the source of the interference, the company responsible and that the problem had been corrected. To say the
least, they were very appreciative of our efforts.

Lou, N3JKM (now K3EMG) filed this report following New Year’s Eve activities by that Township’s police department which operated
DUI Enforcement Check Points and was able to finally communicate again on their radios. “Several car stops were made that evening
for DUI-related reasons. One car was stopped after being clocked at driving 107 MPH!”   

For those who usually associate hams as doing disaster-related communications, this adds a different dimension to saving lives.
As I reflect on Lou’s observations I can only wonder what would have happened had the police been unable to remove those irresponsible
drivers from the roads that evening!  Or what if Lou had simply ignored that digital hash heard on his scanner and locked-out that
channel? The New Year might have started out much differently and tragically for some families. How many potential lives were saved
that evening because of the efforts of a few hams! 

Once again amateur radio had proven its value and, might I say with pride, made a great public relations statement at the same time. 

Reginald Leister-N3KAS
Pottstown, PA
ARRL EPA-PIO
Pottstown Area ARC
Montgomery County ARES-RACES
HRT Liaison Pottstown Memorial Medical Center
ARECC 3 certified
NIMS IS-700,100,200,800a,235,240,242,244
n3kas@arrl.net
An Extra Class Licensee, I have been part of the Boy Scouts of America for 52 years and decided to use amateur radio as a recruiting
tool for Scouting and co-founded SPARK Lodge (Scouts Practicing Amateur Radio Knowledge) at Boy Scout Camp Delmont in the Cradle of
Liberty Council. I am trustee for Station K3BSA. I enjoy organizing and conducting various Public Service events for my community such 
as WalkAmerica. I also serve as a Civil Service Commissioner for Upper Pottsgrove Twp, Montgomery County, PA.

==========================================================================================================================================

I hope that these pictures meet with your publication criteria. I went back to the site and reshot several views and resized them in
the hopes of doing so. While there, I ran into the traffic signal’s Regional Sales Manager who was on site to check on the equipment 
and make sure that it was still working OK. He was VERY appreciative of the efforts put forth by our local ham radio ops especially
when I related what had happened with the restoration of the Police DUI Check Point details! He immediately felt the impact and was
visibly concerned of what ultimate liability his company might have suffered had someone been killed resulting from the police being
unable to intervene with speeders or DUI offenders because of the unlicensed interference caused by their equipment.  I know it is a
stretch. But in today’s liability-laden society, it is not beyond the realm of possibilities. AND their equipment was clearly in the
wrong if it was ever determined that they were the ones at fault. I assured him that the name of their company would not be used in 
any publication of this matter. And I told him that I was going to submit this article and photos for submission for consideration. 
This is why there are no shots of the base of the unit which would display their name. 

Feel free to edit as necessary—especially the picture captions. Was not sure just how much detail you would be interested in.

Thank you for your consideration.