Current Channel lineup - SPVM?

[TurboLed]

I've never known the technical details of the system BUT it's apparent (to me!) from listening while visiting that they are using multiple transmitters to cover the island. If you listen carefully (earbuds) you can hear a slight wooshwooshwoosh on the audio signal. As I understand it this comes from the fact that your receiver is closer to one transmitting site than another and the difference in time of arrival, though **very** slight, is enough to detect on the audio. This occurs despite the fact that multiple-transmitter systems have to be extremely closely synchronized.

That's an interesting theory, but I'm skeptical about it. What would happen when an officer is heard by 2 sites at the same time? The 2 repeaters would receive two signals with different levels, and slightly delayed because of the distance. The result would be a bit scrambled I believe Unless the sites are configured in a single receive-locaition/multiple transmit-location mode, but then how would it be useful for officers to hear but not being able to talk because they are too far from the receiveing site?

 

[plaws]

That's an interesting theory, but I'm skeptical about it. What would happen when an officer is heard by 2 sites at the same time? The 2 repeaters would receive two signals with different levels, and slightly delayed because of the distance. The result would be a bit scrambled I believe Unless the sites are configured in a single receive-locaition/multiple transmit-location mode, but then how would it be useful for officers to hear but not being able to talk because they are too far from the receiveing site?

Receivers are done differently and may not even be at the same sites. Audio from the receivers is sent via landline to a voter and only the one with the "best" audio (I forget how - S/N ratio?) is repeated (and sometimes also fed to the dispatcher directly, meaning field units can be heard even when the dispatcher is transmitting).

As for CWIDs stopping on transmit, that's usually a setting on the repeater. I am trustee for a ham repeater (2 actually) and I'm pretty sure that, at least on the Kenwood commercial unit, I can configure that one way or the other. We have a second receive site, too, but we don't have the cash for a landline or a voter, so we just use a different CTCSS on the other receiver and send it back to the repeater on a separate channel.

 

[TurboLed]

Today I tuned to the 857.5125 channel which is supposed to be the YUL EDACS SPVM channel and found out it's now a P25 trunking channel (not EDACS), with calls taking place on several voice channels (859.4375, 857.9500 and others) with test messages. The messages are P25 digital and say something like: "Vous avez du plaisir à jouer avec ceux qui ont un bon caractère. [...something...] Pour rassembler ses moutons. Ma mère et moi faisons une courte promenade. La poupée fait la joie de cette très jeune fille."

The System ID is 1490E-CFF