Simulcast Over IP

[chpalmer]

We have just installed a three transmitter simulcast system over IP using Harris Intraplex. Being involved in other simulcast systems I was very pessimistic about the ability for the timing to be constant but so far Its doing pretty good. The media it uses for transfer consists of Tsunami radio's, fiber routes, and some networking over microwave.

The system is in Sequim WA. The Fire Dept there will be using it soon. Were doing some final tests now.

The stations are MTR2000's. The clock and ctcss filters are normal off the shelf products. The radio's are within 1 Hz of each other. The system is narrow band.







edit= to clarify off the shelf statement.

[abbylind]

Nice! We've got an 800 Edacs simulcast system here. Works good
Is this VHF or UHF?

Fowler
KC5AEE

[chpalmer]

VHF.

[SlimBob]

How is the required delay calculated? How is the delay implemented?

[chpalmer]

http://www.broadcast.harris.com/product ... WNETXPRESS


The system constantly adjusts for the correct delay so that all site audio is in phase.

[SlimBob]

Fascinating. Thank you so much for sharing.

I've thought about trying to implement a two-site simulcast system, but the problem I have is that both sites are within line of sight of each other and I can make a physical delay line that will pass better than 10KHz of audio. As a result, I never implemented it. I suppose it would be a great exercise if I was using one watt transmitters.

[psapengineer]

SlimBob:

In the analog world you can also measure simulcast delay using a TIMS made by Convex. It measures absolute delay and makes the calculations easy.

By the way, if you use a single Link Tx, a link Rx at each of the two sites, make sure that both sites are identical equipment and, put the Link Tx near the half way point (+\- ~2 miles) between the two you shouldn't need any delay lines.......
.......in a perfect world..........

Bob