Internet STLs?

[slimbob]

Hi guys!

"Someone I know" recently inherited a radio station as an IT guy and has been doing the forensic look at the station. We discovered the other day that the remote transmit site of a two station group is located in a building which as great internet connectivity -- from the same "phone company" as the first station. We also discovered that the existing STL to the remote site is over a T1, and since both the station and remote site are on a metro-ethernet link, we see no reason to continue paying for the T1 over several LATA lines.

I've done a look at the distance between the two sites and discovered there's an old AT&T microwave path along the way (both sites owned by American Tower), of the two sites that would have to be used, both have horns in place. The path is 60 miles "line of sight", but the ends don't allow enough altitude to clear more than 30 miles at most.

So the issues that I'm grappling with at the moment are:

What hardware is out there that supports a "VoIP STL"?
What sort of hardware should we be looking at for a "backup STL"?

My personal thought was to use some of the existing Telos hybrids and order an ISDN line at the remote site and use that for a "dial" backup since audio quality largely isn't an issue, despite the entire group being two FM stations. A degredation to mono audio wouldn't necessarily be unacceptable to the station manager, as long as we keep the transmitter out of silence. Neither myself nor the other IT guy expect any outage to be more than about 60 minutes, and those are usually coordinated for midnights or 5-7AM. (Yes, we have a weird "ISP".)

Thanks for taking the time to read this and reply. Your assistance and ideas are greatly appreciated.

[BroadcastDoc]

Telos, Comrex, Moseley, and even Tieline have audio over IP codecs that work exceptionally well. I use the Comrex Access product myself as an audio link for a station every night from 7p-12a with no problems whatsoever.

Plan on anywhere from $1500-$3000 per side for an IP solution.

For backup, I'd recommend (if you can get it) ISDN with a Telos Zephyr. With it's AAC codecs, you can do stereo audio in very good quality. I have used one of those as a temporary STL at a site for a two month run 24/7 without any ill effects.

[Deep Thought]

Dirty little telco secret...most "program circuits" these days are on a digital 56kbps link, which is basically switched 56/ISDN "nailed up". There is no reason for you to be paying for a full T1 in any case. Equipment has existed for two decades which could provide eight bi-directional 15 KHz channels on a full T1 and you certainly don't need that.

Unless you can get some kind of QoS guarantee from your local ISP I wouldn't be trusting my audio to them full time. As-is, as-available consumer Internet access is a crapshoot and what seems reliable today can go bad if the link gets too busy. If you can get a service guarantee then go for it.

[BroadcastDoc]

Good point!

I had forgotten about "nailed-up" ISDN. That's essentially what telcos are passing off as "equalized lines" nowadays.

[slimbob]

Thanks guys. Yeah, the "ISP" refuses to give us QoS, but when we report problems, they'll give us 100Mbit/ connectivity when we had 10 Mbit/s. Very much a "throw bandwidth at the problem" approach.

[Dale H. Cook]

Very much a "throw bandwidth at the problem" approach.

Bandwidth, however, does no good when it is not available. I'd suggest switching to some other delivery system where you can get a QoS guarantee.

[stephend2]

I'll second not trusting a shared link for STL. I run a wireless isp and I dont even trust my network for mission critical data such as on air audio unless I build out the customer a dedicated wireless path with no other traffic on it.

With that said, the stations I consult for have a t1 circuit at one site, bridging ethernet over it with cisco 2610 routers, we're using it for STL as well as a return path for RPU, also for a surveillance camera at the site as there have been some issues out there, finally we're sending RDS data to the encoder over it. Using comrex BRIC Link for audio over IP, has been a great pair of devices, set them up and forget they even exist as long as they're on a good circuit.

I'm using some barix boxes on a wireless link for an AM, they work pretty well but are not as tolerant of connection faults as the comrex units. I also just recently had a barix hardware failure, luckily I had a spare encoder on hand.

the wireless link there has been good, tranzeo tr-902 on stl antennae so in a pinch I can throw the old marti stl-8 on and keep going. again, using the connection for more than just audio.