Joe Iannucci
New Participating Member
I listen to an AM station with a daytime and nighttime pattern. I hear static sometimes around sunrise for a brief second. Is this when the pattern and power is adjusted?
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AM Night and Day
- Thread starter Joe Iannucci
- Start date
Yes, you have he general idea.
At pattern change, the transmitter goes off, a pbig automatic switch is activated to switch to the appropriate network, called a phaser, that creates the day or night pattern, and the the transmitter turns back on. This can be done pretty fast if well designed and the best components are used.
Sometimes separate transmitters are used if the power differences are big. Other2ise, the same transmitter goes into “idle” and is not fully off. It is ready to vote back at the right power so the change can really take little time. Some of us counted on the speed of the relay and hot switched without turning the transmitter off. That required regular changes of the relay contact and was unpleasant if the relay stuck.
But yea, this is part of changing between day and night operation
Joe Iannucci
New Participating Member
So are you saying the change in patterns is always pretty fast or can it take awhile depending on the equipment?
It can be almost instantaneous... sort of a sparking effect... or take a second or two.
Most modern AM transmitters have a 'carrier mute' mode used during the switch. When the command, usually from the remote control, is issued to the directional antenna pattern controller in the phasor to change modes, the transmitter is sent a mute command until the switches at the towers and phasor have confirmed everything is in position for that antenna mode. As David mentioned, any delay depends on the speed at which all the switches move and send back confirmation they are in the correct position. There are microswitches on the much larger RF switches which confirm to the controller, what position the RF switches are in.
Grounded Grid
Frequent Participant
It can take some time to do the mode changes, if the system design is not current.
On one hand, I have a site that uses a commercial pattern controller. It goes through all of the required steps to change mode and transmitter power levels in about half a second. You almost miss that the transmitter has dropped out.
On the other, I have two sites that require the transmitter be completely turned off while changing modes. Because the steps are done in sequential order, the whole process takes nearly 10 seconds to complete. The station is off the air completely during that transition. Added to that, the transmitters don't "switch on", but gracefully "fade up", adding to the perceived time it takes to complete the process. Until recently, one of my stations was down for 20 seconds while switching took place. That was a bit of a kludge job, and I've changed all that since... now, it's about a second and a half.
We also have a station in our market that uses separate sites for day and night operations. I haven't seen how they do the switching or what equipment they use, but one site goes off the air and the other switches on at least 10 seconds later. You'd think that could be tightened up, but it's been that way as long as I remember, so maybe there's some reason for it.
In any case, you've noticed something that is a normal, planned part of the day for whatever station you're listening to. Those times move around at the first of each month, depending on the sunrise/sunset time for that station.
On one hand, I have a site that uses a commercial pattern controller. It goes through all of the required steps to change mode and transmitter power levels in about half a second. You almost miss that the transmitter has dropped out.
On the other, I have two sites that require the transmitter be completely turned off while changing modes. Because the steps are done in sequential order, the whole process takes nearly 10 seconds to complete. The station is off the air completely during that transition. Added to that, the transmitters don't "switch on", but gracefully "fade up", adding to the perceived time it takes to complete the process. Until recently, one of my stations was down for 20 seconds while switching took place. That was a bit of a kludge job, and I've changed all that since... now, it's about a second and a half.
We also have a station in our market that uses separate sites for day and night operations. I haven't seen how they do the switching or what equipment they use, but one site goes off the air and the other switches on at least 10 seconds later. You'd think that could be tightened up, but it's been that way as long as I remember, so maybe there's some reason for it.
In any case, you've noticed something that is a normal, planned part of the day for whatever station you're listening to. Those times move around at the first of each month, depending on the sunrise/sunset time for that station.
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