Tue February 5, 2013
TheEC: Satellite Dishes and Snow
Oh the weather outside is frightful…
Actually, this winter we haven’t seen too much snow. Nevertheless, snow is something of a chore for us at RIPR, because it builds up on our SATELLITE DISH, which blocks the satellite signal. Specifically, our NPR and BBC signal, and that means when it snows = dead air on RIPR!
Traditionally most stations have their satellite dish located at their studios, and they detail a couple of staff members to keep an eye on the signal levels and, when they get too low, go out on the roof and brush the snow off the dish with a pushbroom.
Since NPR dishes are usually 3.8m (12.5ft) in diameter, that can mean quite a lot of snow! And it’s a rite of passage to not warn a first-timer to avoid standing directly in front of the dish when you clear it (thus ending up with a mountain of snow cascading onto your pants).
Because there’s nowhere to put it at 1 Union Station, RIPR’s dish is five miles away in North Providence, at our old 1290AM site. So clearing it gets more complicated. This year your intrepid engineer had a brainstorm and rigged up some insulated vent tubing, several vent fans, and ductwork to the adjacent building where the 1290AM transmitters are. That ductwork, in turn, goes to the main hot air output of the furnace inside the building (which is not regularly occupied).
The result is that now the furnace blows hot air out into the cavity between the satellite dish itself and the vinyl cover over the dish. That hot air warms up the dish cover and melts any snow or ice attached to it! At least in theory; we haven’t had a major storm since I completed the installation. First time I’ve ever really wished for a major blizzard to come through!
While this idea was simple in theory, it proved devilishly tricky in practice. It’s surprisingly difficult to get enough heat into that space to melt any snow on the cover. You’d think even room temperature air (about 70 degrees) would be more than sufficient but it’s not even close; you lose a lot of heat in the ductwork even though it’s only 25ft or so, and 6 inches in diameter, and well-insulated. It took getting temps up to around 120 degrees and airflow up above 1000 CFM to overcome outdoor temps frigid enough to allow snow/ice to build up in the first place.
Still, nowadays us engineers and operators should be able to remain toasty warm INSIDE while our satellite dish stays nice and clear even when nature lets it snow, lets it snow, lets it snow!
Ed.Note: This article was written just two weeks before "Snowmageddon" in mid-February 2013 (aka "Winter Storm Nemo") that dumped 18 to 22 inches of snow across Rhode Island in one night. I'm pleased to report that the dish heater did, just barely, manage to keep up with the snow and kept the dish just clear enough to maintain the satellite downlink we get our NPR programming through. It also worked well during subsequent snowstorms.