As I’m sure you all know, The Public’s Radio (my day job) is a National Public Radio affiliate station. Meaning we air many of the same programs, often at the same times, as hundreds of other NPR affiliates across all fifty United States. And the entity that manages that is the Public Radio Satellite System, or PRSS. Part of NPR Distribution, PRSS maintains a massive “Network Operations Center” or “NOC” (pronounced “knock”) at NPR HQ in Washington DC, and a fully redundant backup NOC at Minnesota Public Radio’s (American Public Media) facility in St Paul. Working in the 3.8 to 4.2 GHz “C” band, they beam a signal over 22,000 miles up to a geostationary satellite over the equator (at 99 degrees longitude, which is about 500 miles west of Ecuador) called Galaxy 16.

Why pricey satellites? Why not just use internet? Well first, there’s quite a few places in America (and not just in Hawaii and Alaska) where fast, reliable internet is a given. And second, the way all those 600 affiliate stations manage their transitions from national to local and back to national programming is through precise time-synchronization. The quality of internet reliable enough to deliver that precision…where it’s even available…would cost so much because it’s so many radio stations, that it’s cheaper to just keep using satellites.

In PRSS’s case, we use 3.7 meter (a bit over 12ft) diameter Prodelin-made fiberglass parabolic satellite dishes. That huuuuge dish takes that faint signal from Galaxy 16, over 22,000 miles away, and amplifies the heck out of it. Focusing everything coming in over a 12ft swath onto a feedhorn barely an inch wide.

Fiberglass Senescence

While fiberglass lasts a long time, even under adverse weather conditions…it doesn’t last forever. In our case, WBUR installed our old Prodelin dish in 1998 when they bought then-WRCP 1290AM. Lacking a formal studio yet (it came a year later in 1 Union Station) they put the satdish at the 1290AM transmitter site.

This presented numerous problems. First off, it required expensive T-1 lines (later replaced with fiberoptic networking from OSHEAN and Verizon FiOS) to transport the audio with high fidelity, high reliability, and sub-second delay to wherever the studio would be.

Additionally, at the time most of the tower field for 1290AM was Geneva Pond, formed by a mill dam that would collapse (and the pond disappeared) in 2010. But in 1998, it meant the satdish mostly hung out over the water. Performing any sort of maintenance was a big hassle.

Still, lacking any other option? We made it work. And in 2013 I constructed my own custom-made hot-air heater to keep snow off the dish (snow kills C-band signals), later updated and improved in 2015 with a Walton De-Ice SnowShield cover, and again in 2018 with better controls.

But by 2022 it was becoming obvious that something was amiss. My signal readings, typically measured in Eb/N0, had fallen from a healthy 10 or 11 to 6 or 7. Even more troubling, signal levels would plunge whenever there was merely water in the air. It wasn’t just that the dish cover was getting wet. It was the presence of rain or even heavy mist that would knock signal levels down to a perilously low 3 or 4 (usually below 2 is when the receivers “un-lock” and lose signal/audio).

And to add insult to injury, PRSS had just migrated all our transponders to new frequencies after the FCC auctioned off a good hunk of the spectrum to wireless carriers for 5G purposes. Not only did we need to install new LNB and other hardware, now we had to worry about significant sources of interference coming from spectrum right next door to our own.

After replacing the RG11 RF cable, the LNB, and the 5G filter…and re-aiming the azimuth & elevation (az/el) of the satdish and checking the polarization of the feedhorn…all with no improvement. We’ve inferred one of two things has happened:

1. The 25 year old fiberglass of the satdish itself has warped, negating the focus of the dish, or…
2. The boom arms of feedhorn are bent, putting the feedhorn in the wrong spot and/or the wrong angle.

Either way, it speaks to how this satdish is old and needed to be replaced! Unfortunately, the primary vector for funding projects like this was the now-defunct Public Telecommunications Facilities Program. A victim of the Congressional Republican budget cuts in 2011.

A Ray of Light…From Geostationary Orbit

Fortunately, we got lucky: the Corporation for Public Broadcasting (CPB) has a limited amount of funding for PRSS to provide GEAR Grants. Just enough for projects just like this.

Better still, there was sufficient funding to not only replicate the setup we had, but improve on it by using a proper Walton De-Ice electric hot air heating unit mounted beneath the dish…dramatically shortening the distance heated air has to travel to get into the space between the cover and the dish.

Over the past two weeks I’ve been working extensively with Andre Concrete & Excavation to dig and pour the 5x3x3ft concrete base, and with Allied Satellite & Antenna to assemble & install the dish and heater.

As of Friday September 9, 2023, the new dish is online and in-use as our primary downlink from PRSS. And I’m pleased to report that Eb/N0 levels immediately jumped from 7.5 to 11dB after the switchover. Better still, during today’s heavy rains? No change in the signal at all. How well this thing performs in snowstorms will, uh, have to wait a few months, I guess. 🙂

Next up is our electrician has to come out and wire up the 220VAC for the dish heater, and I need a chainlink fencing contractor to replace the temporary fencing with a permanent solution, including some large swinging gates.

That’s important because part of this process is to make a 5ft-wide gap that a brush hog can get through and get down into the weeds…literally…that are growing out of control in the area between the dishes and the West River running through the 1290AM tower field. We’re already uncomfortably close to some trees being tall enough to physically block the dish’s “look angle” into the sky to get the satellite signal.

Put Out on the Ice Flow?

So what happens to the old dish now that this shiny new one is in place? Do we just shove it out on the ice flow with grandpa??? No, of course not. 🙂 Even if I had no use for it at all, it would cost too much money to actually take it apart and dispose of it. But fortunately, I do have a use for it: a backup dish.

One of the biggest problems with the old dish is that we only had one dish. So any diagnostics and repair had to be done within a very narrow time window: approx 50 minutes, thrice daily, when we aired programs from our Enco DAD Automation computer at the studios. It made any work that had to be done very stressful and difficult.

Now I have two dishes! Even if the old one doesn’t perform well, it’s good enough to keep things going for a few hours, even a few days, if I need to do major work on the new dish. Such as, replacing the dish cover in about 6 or 7 years. Or any other routine maintenance.

Yeah, Yeah, Less Talk, More Pics!

Okay, okay – here’s a bunch of pics from the process. 🙂