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FM Transmitter Heat Safety Mode

L

Luckeeeme

Guest
I have a 500 watt transmitter (Broadcast Electronics Model BE522C1). In the heat of the day we lose signal about 30 miles away but the signal in the general three mile area is still good. Is there such a thing as a heat sensor on Transmitters that would be the reason for this happening? Can you explain how these work? Thank you.
 
If the transmitter power is stable then this probably is related to propagation conditions that are changing over the course of the day, and affect long paths more than short ones.

If you post the call letters of the station and the location(s) 30 miles away where the signal is changing then a better evaluation can be made.
 
Humm, a station with 500 watt TPO with a signal that reaches 30 miles? Something isn't adding up here unless you are sitting high up a mountain and are a de-rated A. Even then, a 30 mile reach is a stretch. I'd be interested in your call letters, too.
 
Any FM broadcast transmitter I've ever seen has a watt meter or some kind of relative output metering. If your coverage if dropping from 30 miles to 3 miles you should see a tremendous drop in output power.
As far as heat sensors, yes many transmitters have an over temperate fold back or shut down to protect it from thermal runaway. How it works? When the transmitters internal temperature reaches a certain level it will start reducing the power until the temperature drops to a safe level. In some extreme cases it can even shut the unit down.
Most transmitters with this protection have some kind of indicator for over temperature oif it is in this mode.
You state this happens in the heat of the day.What is the temperature of the building? Are the air inlet filters to the transmiiter clean? Are the fans blowers operational?
What does your engineer say?
 
I do know one thing about the Harris Z series transmitters and heat... You want to make damn sure you've got a temp. alarm on them that will open in the event the room gets too hot. Heat is about the only thing that will kill the beast, and unfortunatly they designed it to pretty much stay on the air regardless. Other than that, the Z is one of the finest FM transmitters ever built. Kept cool, dry and clean they'll last decades without failure in most cases. I realize the original post was about another lower powered transmitter of some sorts, but I figured I'd share a piece of advice that'll potentially save people thousands in damage, etc...
 
A caveat - every year or so withe the Z, pull the modules out, take the dust cover off the pallets, and snug up the scrws which hold them to the heatsink. Differential expansion over time loosens them, and a lack of good contact will eat the devices on the pallets. Past that, they're a little over - complex and the parts can get pricey... but they run reliably for long periods of time.
 
Thanks! Yeah. I've heard things needed to be tightened up, but I didn't realize it was the pallet hold-down itself. I've got a new ZX I need to make sure is tight in about another 7 months then. Thanks for the info again!
 
The last rebuild I got came with a pad for heat transfer instead of just the white paste. I suspect it does a bit better job of holding things together, in that it had a bit of thickness to squish and hold tension on the screws. I still tighten them regularly though, and consequently have little or no trouble with the boxes.
 
Thank you all so much. Ended up putting a new AC in the building which seemd to take care of the problem. Also took the advice to clean things up as suggested.

By the way never disappeared just kept reading posts. I do find it a bit odd that anyone would be a BengalsFan and state that publically. Total win loss record in 40+ years 285 wins 373 losses.
Only been to the super bowl twice ever and lost both times in 1981 and 1988. Only made it as a wild card team into the playoffs since 1989 three times only to lose all three times. You only get one life. Maybe time to change and see what it feels like to be a winner?
 
Luckeeeme said:
Thank you all so much. Ended up putting a new AC in the building which seemd to take care of the problem. Also took the advice to clean things up as suggested.

By the way never disappeared just kept reading posts. I do find it a bit odd that anyone would be a BengalsFan and state that publically. Total win loss record in 40+ years 285 wins 373 losses.
Only been to the super bowl twice ever and lost both times in 1981 and 1988. Only made it as a wild card team into the playoffs since 1989 three times only to lose all three times. You only get one life. Maybe time to change and see what it feels like to be a winner?
Click to expand...

Thank you, luckeeme, you just proved the theory I had about you.
 
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