Bitter Cold vs. Radio Towers

[DJ Jim Wayne]

Just curious; do engineers need to prepare towers for the bitter cold? For example, if ice builds on the FM probes or the AM stick, does that screw up the signal? Perhaps NECRAT could answer this.

 

[rcs]

Many FM and TV antennas use either fiberglass covers, called radomes, or electrical heaters to prevent ice build up. Most AM towers are impervious to ice although some critical directional antennas have been known to drift with severe ice. AMers that use folded unipole antennas sometimes also experience problems.

 

[Tom Wells]

A few weeks ago when Chicago had gotten some freezing rain, I think WGN 720 had an icing issue, and on audio peaks, it would arc
over somewhere and knock the transmitter off for a split second. Over and over again.
Never ever heard that before on WGN.

 

[necrat123]

To follow up on what John said, if Ice builds up on the FM antennas, it can cause the power to reflect back to the transmitter. If the transmitter doesn't automatically reduce the output power based on the reflecting power, you will have a build up of heat and burn something out.

A problem ICE can have is, it can sometimes ground ungrounded towers. ive read about scenarios where the ice buildup is thick enough to short out the Johnny balls on the bottom of the AM tower.

 

[RonTheEngineer]

To follow up on what John said, if Ice builds up on the FM antennas, it can cause the power to reflect back to the transmitter. If the transmitter doesn't automatically reduce the output power based on the reflecting power, you will have a build up of heat and burn something out.

A problem ICE can have is, it can sometimes ground ungrounded towers. ive read about scenarios where the ice buildup is thick enough to short out the Johnny balls on the bottom of the AM tower.

But the absolute worst case, the ice only lasts a day or so. TV and FM antennas have either radomes, which ice simply doesn't like to stick to (fiberglass vs steel) and if it does, its no big deal, or de-icers that gently heat the antenna above freezing. Its important to turn on the de-icers BEFORE the storm. At WSAH, our old Bogner NTSC antenna had de-icers as it was 99% solid steel. Our new Dielectric has none as it is entirely covered by fiberglass radomes, and I asked them 3 times if they were sure I didn't need them.

In CT all of this depends on a very specific set of circumstances to happen. Of 10 years at WSAH, we had ice ONCE. Of 4 years at WTXX, we had ice maybe 3 times. And of 3 years managing Meriden Mountain, never. Snow doesn't do it, rain doesn't do it, it needs to be messy freezing rain / wet sloppy snow with rain mixed in there. Fairly rare, maybe once a year, generally in early winter. Your mileage will vary in other climates (like accretion ice on Mt. Washington)

But, generally the next day, the radiant heat of the sun comes along and loosens it all up and it falls off pretty quickly. Even if its below 0, the sun is still providing radiant heat.

Dishes are another matter. Snow itself does not attenuate the satellite signal appreciably, ice is transparent at microwave frequencies (which is what snow is, crystalline ice). "Snow in the dish" always happens after the sun comes out after the storm and begins to melt the snow, a layer of water forms under the snow cover and you have your outage. A good amount of the time you can simply wait and the snow will slide out on its own. Poking it with a long handled broom will also hasten it sliding out.

Now extreme cold can play havoc with the lights. Not the red beacons and sidelights as they are basically just plain lightbulbs, but strobes, the xenon flash tubes and supporting electronics just don't like the cold. The WTXX strobes have been out for awhile now, and I've seen both the WTIC and WVIT top strobes mess up in extreme cold.

 

[HarrisGatesFM10H]

Ron, which plants did you manage on West Peak? also, does anyone know if WMRQ ever fix or replace their antenna? at the time of the sale they filed with the FCC that they were running at 75% of power due to antenna problems.

 

[RonTheEngineer]

Ron, which plants did you manage on West Peak? also, does anyone know if WMRQ ever fix or replace their antenna? at the time of the sale they filed with the FCC that they were running at 75% of power due to antenna problems.

The Schultz property at 101 West Peak Drive. its the one between the SNET tower and the Gilmore property. The one where 104 and 95.7 sit. CC took care of their stuff, I took care of the Schultz owned towers and building.

Schultz sold it off to CC in 2006