Engineer's Corner
6:10 pm
Fri July 18, 2014

TheEC: New STL at 88.1FM

RIPR Chief "Engneah" poses with the STL antenna
Your Intrepid "Engneah" poses with the new 950MHz Microwave STL transmit antenna on the roof of WELH's studios on the Wheeler School campus.
Credit David Schiano

UPDATE 7/22: After a weekend of solid operation, we've moved out of "beta" and into "gold", meaning when you listen to 88.1, you're hearing audio that's coming across the new microwave STL.

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Good news everyone!

Longtime Engineer's Corner readers know that we've had, well, "issues" with the STL or "Studio/Transmitter Link" for our 88.1FM signal in Providence.   The STL is what carries the audio from our studios in downtown Providence to the transmitter/tower at the Wheeler Farm in Seekonk.

Now a couple weeks ago we revealed that half of a new wireless microwave STL was installed, and that the other half would be installed soon.  Today, we fired it up for the first time and the results were gratifyingly positive!

Plenty of signal, despite a path aimed right through a stand of trees along Stimson Ave on College Hill.  And the audio coming through is crystal clear!

Moseley STL receiver
Moseley PCL606 receive unit at WELH transmitter.
Credit Aaron Read RIPR

 Of course, it helps that we're using an old (but refurbished) Moseley PCL606 pumping out 20 watts on 948.5MHz, into a Kathrein-Scala MF-950B "Miniflector" parabolic antenna with a whopping +16dBi gain that blasts 800 watts over a mere 5 miles (microwave STL's are often good for 20 to 50 miles) to an even bigger Kathrein-Scala PR-950B "Paraflector" parabolic receive antenna with an equally whopping +18dBi gain.  That bad boy will straighten your hair out, man.

You might justly ask, what's the big deal?

This new wireless STL means that RIPR is no longer dependent on a third party telecommunications company, like Verizon or Comcast, to deliver audio to the transmitter.  That's really important during severe weather (blizzards or hurricanes, or even just bad thunderstorms) or other times when phone lines or internet connections can simply "go away".  And it can take hours before a tech can even be dispatched, much less find the problem and fix it.

For a big company like Verizon, a comparatively tiny account like RIPR can't cost-justify putting all the time, money and effort into making a bulletproof system.  But for RIPR, we most certainly can justify it because every second off the air costs us listeners!  This wireless system is completely telco-independent; it's all engineered by us.  So now we have the freedom to spend that time and money to make it bulletproof.

To be fair, we do still rely on third parties here.  Power, for example.  There's a battery backup at WELH's studio on the Wheeler Campus that'll hold for an hour, but no generator for long-term outages.   And we still have a Verizon "digital line" from 1 Union Station to WELH on Hope Street; that line has been very reliable (in no small part because the lines are almost entirely in underground cable vaults, and it's a much shorter run that doesn't cross a state line).

But now the most problematic part of the system has been completely replaced with a much more reliable system.  This is very good news that helps your Intrepid Engineer sleep a lot better at night.

Plus we've still got our handy Comrex BRIC Link audio codecs for a backup STL, plus a radio tuned to our 102.7 signal as a backup-backup STL.

And not to deflate the balloon, but actually, the new microwave STL is technically in "beta testing" mode.  We're not relying on it for real operations just yet; not until we've tested it for a few days.   But if things go well over the weekend, we'll switch it in and start using it Monday or Tuesday for live operations!  Glee!!