We just finished our 3rd annual February ice storm. It is becoming somewhat of a tradition in these parts. After shoveling the driveway this morning, I sat down to enjoy my nice hot coffee. While doing that, I figured I would check some of the transmitters to see how things were going. That is when I noticed this:
The reflected power is much higher than normal indicating potential issues with the antenna deicers. I knew something was wrong after a quick call to the Burk, which stated the deicers were on. A quick double-check showed that the reflected power had increased by another 75 watts, so a nice drive to the transmitter site was in order.
Indeed, the controller had turned on the antenna deicers.
Using a clamp on amp meter, I saw almost no current on either leg of the 240-volt circuit. In the meantime, the backup antenna had 2 amps on each leg, which is normal. Then I noticed this:
The relay on the right shows signs of overheating.
I moved the Main Antenna circuit over to the aux antenna relay to get things going again. The current on each leg of the main circuit is 4.2 amps. Over the next 45 minutes, the reflected power returned to normal.
Other transmitter sites to the north in Albany have had similar issues. Unfortunately, those antennas do not have heaters or radomes. Thus, the only remedy is reducing power until the transmitter stays on.
I also noticed that when there is an antenna problem, the station does not sound as good as it normally does because of the bandwidth restrictions adding distortion in the frequency domain.
“ Other transmitter sites to the north in Albany have had similar issues. Unfortunately, those antennas do not have heaters or radomes. Thus, the only remedy is reducing power until the transmitter stays on.”
Ahh yes – I used to work for that exact company and remember how crazy that was when both of the 50kw stations would be at low power and it blew my mind that they never invested in deicers or radomes. The general consensus (correct or not) was radomes were a no go for the one tower because of weight, however the other big station was on its own tower which I’d assume could handle it. And deicers aren’t a weight issue. Then again, ice is heavy itself. Probably was just the excuse instead of it being the usual reason there – the owners were/are exceptionally cheap.
Need to double the amp rating on those relays.
I’ve had to replace too many “spec” relays in HVAC and the like, especially in loads that have a high starting current.
Bill, you bring up a good point about the contactor ratings. I’ll order better one.
Brian, you understand some of the problems. For both stations, radomes are a no-go because of the age and size of the towers. One tower was built in 1947 and the other in 1970. Neither would pass a structural study with radomes on the FM antennas. I think, in at least one case, the lack of antenna heaters was simply an oversight. Hopefully, during the next antenna replacement cycle, this gets resolved.
Guess what they said was true that the towers couldn’t support the radomes. Knew the one tower was 1947, didn’t know the other was 1970! Thought it was 1990s but then again never asked. That tower could have a shared antenna for at least two of the three stations, but the third being directional makes one master antenna a no go. De-icers would definitely be a welcome upgrade.
Funny story – one morning the show that was in the studio where the meter readings computer was were complaining that their signal was all static. One of the personalities mentioned he was “clicking around” the meter software because for some reason their signal was weak and people were complaining and now it was all static in the studio. He wasn’t the brightest guy. I looked at the meters and told him the main was on fold back because of reflected power due to ice so that’s why it was a weaker signal – then I noticed he had also put the aux on the air too. ♂️ I turned off the aux and the static stopped and tried to explain to him what he did and that the station was interfering with itself. This is why most DJs shouldn’t have access to this sort of software without knowing what they’re doing
Would an appropriately rated solid-state relay be a viable option, rather than using a mechanical contactor?
David, A solid state relay would work in this situation, however, the deicer controller uses 120 VAC as the control output. We would need to install some type of DC power supply as most solid state relays use 2-32 VDC for control. That would be another potential failure point.
Brian, that is pretty funny. I think we should be working on an AI remote control system (which might be more reliable that DJ’s)
We took all transmitter control away from the “DJs” (so few of them anyway) years ago. Some stations still do the manual EAS tests, but not all. One does a RMT once a year (LP2).
Anywho, I always dreaded the call from “FM Line A or B” on the phone. Dual feed CBR on a 7200′ mountain.
Not anymore! Retired!!!