sounds like EDACS analog trunking... whenever i drive thru lincoln, ne.... it sounds exactly like what you got there... except for the BURST in front of the transmission. but i hear the same noise as if it is interference. edacs is ericsson radios version of trunking btw
Some EDACS systems are intentionally programmed to cause that on scanners. EDACS systems have a signal encoded in the sub-audible data to indicate an end of transmission and return to the control channel. They also have a signalling tone (several beeps) which can cause radios to go back to the control channel. System administrators have taken to fiddling with the timing and level controls on the controllers, repeaters and radios to make them non-standard and help confound casual scanner listeners. Some scanners will be more sensitive to this than others.
The Worcester MA EDACS system has an occasional burst of control channel noise - not every time like your clip; but still there. It probably comes from the way EDACS channel following was found out by scanner manufacturers - they had no help from the people who make EDACS trunking radios so it's sort of a hack.
Still - better than nothing I suppose. You might try resetting your scanner and reprogramming that EDACS system making sure they didn't change the channel order or something on the system by looking up the site info on RadioReference.com
Very common on EDACS systems and seems to be very system dependent. We had an EDACS system down here that did this on every transmission and other EDACS system where it is never heard. There's even a LONG version. It's some kind of channel clear or end of transmission signal. I understand that system users don't hear it.
It is the noise of the data when the system is granting the channel. Try adjusting the EDACS unmute timer so that it does not unmute until the channel is actually granted and you don't hear that data burst anymore. It sounds like the timer is set too low if you are getting it with every transmission. Try 16 or 18 as a default and then go from there. 16 works great with my local EDACS system. Anything lower causes the noise to be heard with every transmission or channel grant. Of course, this is on my PRO-106 and PSR-310. Haven't had to mess with it on my BC346XT as I never hear it. Unless, that is, the longer burst occurs.
The longer bursts, I think, are usually caused by a busy system trying to find an available channel to grant the communication to. The actual radio user hears a low tone, meaning there is no access to an available channel and the radio is not transmitting, until the channel is granted. Scanners, unfortunately, just receive the data bursts until the channel is granted. This is more noticeable on the sites that have the smaller channel capacity and a high volume of calls. Even if you change the EDACS unmute timer to a longer time, you may still hear an occasional long burst.
If any part of this is wrong, please feel free to correct me. I am not an EDACS TRS sysop so it may be wrong. I just know that I get the same noise at the beginning of each transmission if I set my EDACS unmute time at a low setting. I try to get the length where the scanner unmutes just after the short burst is gone so all you get is the actual comm and not the data burst.
We don't have any EDACS systems around here locally so I can't play around with this but where I go on vacation I used to hear this from one of their systems on occasion. I haven't been there in a few years to see if it still does it.
But I'll go the other route on this. I love hearing the identifiers on the radios even though ironically my own personal portable is ancient and not able to do MDC. Well it could but I'm not going to hunt down the programming for it right now, I'll eventually just get a new portable when it finally dies. So I like hearing the data bursts like this. It's a weird question but if 16 or 18 would help eliminate hearing them what do you recommend adjusting the settings to in order to be able to hear more of them without setting it too low?