Served Agency Requested Assistance During Field Day by Robert KM6RSS

On Field Day Sunday morning, at about 10:00 AM, I observed an Oxnard Police car drive into the parking lot and stop across from my (Burt’s) pop-up. Since we have many members in our club who are Auxiliary Communications Service (ACS)/ Amateur Radio Emergency Service (ARES), the Oxnard Police Department are one of our served agencies and we always welcome them to visit us for Field Day and other events.

The sergeant approached me and identified himself as Sergeant Jason Radcliffe KN6JYL.

Sergeant Radcliffe mentioned that the Oxnard police dispatcher had noticed interference on frequencies they used (Channel 1 and 2, with Jeremy KN6JMD supplying the specifics of 154.875 and 155.745 with a PL tone of 100 Hz). I had been working the 2, 1.25 and 0.770 meter bands but had stopped my QSOs while the officer was discussing the issue.

I contacted Dave, Jeremy and Phil and, together, we listened to Jason’s handheld radio for the interference. Dave walked the site and found that none of us were currently on 2M, though the interference was currently happening.  He tuned to their output frequency and left the squelch open, hoping to hear a callsign, but didn’t.  The speech was distant, and seemed to be everyday dialogue, not someone participating in a QSO or FD exchange.  Given it was cutting in and out, and was infrequent, he wondered if the problem was a mixing problem.  Actually, as he thought about it, he wondered if their front end was getting swamped by someone near dispatch with an amplifier.  Oxnard PD runs a PL tone, which Dave thought would have prevented the interference, but he could hear firsthand what they were hearing. Dave also checked the frequencies for heterodyning,  intermodulation, spurious emissions, even duplex systems issues, since duplex systems don’t have out of band rejection, don’t have isolators, don’t have true passband filters, etc.

We offered Sergeant Radcliffe lunch but he had other duties and thanked us for our assistance. I did have him sign our Visitor’s Log, Dave gave him our club card and invited him to join us at one of our meetings.

From left to right: Dave AI6VX President VCARC, Oxnard Police Department Sergeant Jason Radcliffe KN6JYL and Phil Cohen WA6BUZ Secretary VCARC

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