Thursday, November 21, 2013

US Capitol Police Trunked System On The Air

I just started monitoring the new US Capitol Police VHF P-25 trunked system that should replace the analog VHF conventional channels that are currently in use.

Here is what the system that is on the air is showing for details at this time:
SYS ID - 582
SITE - 001


No affiliations or channel grants are being shown right now, as previous new reports were that the system is on line for coverage testing.

Wednesday, November 20, 2013

Coast Guard Data Bursts?

I have recently seen complaints from multiple locations about hearing some sort of digital noise or interference on the Coast Guard primary air operations frequency of 345.0 MHz. I thought I was not hearing it myself, but I set up one of my tunable wide-band receivers on this frequency and did hear it clearly when I opened the receiver squelch all the way.

What I am hearing is a series of short bursts  of noise, almost like a burst of machine gun fire. The length seems to be from 4 to 6 "bursts" in a group, although some have been two groups of 4 or more in a row. I can also heard weaker stations followed by bursts from stronger stations. Sometimes the bursts are at a moderate tempo, and some seem to be very rapid compared to others.

Here are some short clips of what I heard. Turn the volume up when watching these:

At first I wasn't sure if these noises were intentional or just some form of interference, but after  hearing them and listening to the patterns, I am guessing they are intentional usage of the frequency by the Coast Guard. As to what this is used for and why they are using this frequency remains a mystery. Anyone want to guess at what's going on here?

Sunday, November 17, 2013

State Department 409.5250 MHz Work in LA

While in the Inland Empire near LA, I caught someone doing some work on the State Department's Diplomatic Security Service (DSS) repeater on 409.5250 MHz, N293. Besides a test tone, they were looping a test audio track of a man and a woman reading sentences that test the readability and the quality of the digital encoding & decoding. You can hear some of the errors that occurred while I was monitoring.

Eventually it sounded like they got the errors to a minimum, at least by listening to the audio tests. This went on over a couple of days this past week.