Never seen a blinking light on a tower in Norway. Why the difference between countries, can’t be that huge difference risk if some don’t have them?
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Why do some radio towers blink?
51–60 of 131 posts
Re: Why do some radio towers blink?
#52> Joe: [...] So whenever there's a project on the tower, it's not unusual to see the guys in some kind of a, what do they call those? > Jeff: A full ghillie suit? Or I don't know what they're called. If you see someone up in a tall tower wearing a ghillie suit [0]... that sounds like time to call emergency services while avoiding their line-of-sight. :p (Perhaps they meant "Hazmat" [1]) [0] https://en.wikipedia.org/w…
Haha, yes. For some reason, ghillie suit was the only thing I could think of at the time. I think they wear basic tyvek suits while doing paint work, not sure if they need full hazmat (maybe if the tower has lead paint?).
Re: Why do some radio towers blink?
#53Earlier quoted context omitted.
If they don't sync to a common clock source, they won't stay in sync for long. Probably not even for a few minutes or so. You'd get the same phenomenon that you see when operating turn signals in traffic. They seem to weave "in and out" of sync. The frequency at which that happens is the beat frequency, i.e. the difference between the two blinking frequencies.
There's got to be some rubidium frequency standard that's a drop-in replacement for a 555 timer ;)
A chip scale atomic clock (with a handy 1Hz output) can be yours for barely over five thousand euros and half that if you buy 250 of them. https://www.microchip.com/en-us/product/csac-sa65
It's a bit larger than a 555, but it should keep you within a small handful of microseconds per day until the aging effects start to add up which make getting more than a millisecond a year dicey, even if the thing doesn't die on you: https://www.ipgp.fr/~crawford/2017_EuroOBS_workshop/Resource...
Re: Why do some radio towers blink?
#54Blinking uses less power.
Re: Why do some radio towers blink?
#55Earlier quoted context omitted.
It's probably just a side effect of them being powered on at the same time or not?
If they don't sync to a common clock source, they won't stay in sync for long. Probably not even for a few minutes or so. You'd get the same phenomenon that you see when operating turn signals in traffic. They seem to weave "in and out" of sync. The frequency at which that happens is the beat frequency, i.e. the difference between the two blinking frequencies.
Wouldn't the mains frequency be a common clock source, if nothing else?
But presumably these lights at least have battery backup, given the obvious risks in case all of them were to fail at the same time due to a grid issue.
Re: Why do some radio towers blink?
#56Slightly off topic: typically, lights of neighboring towers blink asynchronously. But sometimes they are synchronized. Very satisfying. Anyone knows how this works? My best guess is e.g. DCF77. Thoughts?
I believe it's usually GPS/GNS (they all receive the time via GPS independently, and flash at predetermined times). The FAA requires synchronization for many classes of obstruction because it makes it clear that you're looking at obstruction lights rather than e.g. brake lights or traffic lights on the ground.
Could they also use power grid sync? Not sure as I haven't talked to anyone in wind power, but grid sync would be pretty close to 1 Hz at least in the US.
Building a product that would sync at 1 Hz via GPS that works in the US and other countries with 50 Hz power would be a little easier than syncing to grid phase though.
Re: Why do some radio towers blink?
#57Re: Why do some radio towers blink?
#58Earlier quoted context omitted.
If they don't sync to a common clock source, they won't stay in sync for long. Probably not even for a few minutes or so. You'd get the same phenomenon that you see when operating turn signals in traffic. They seem to weave "in and out" of sync. The frequency at which that happens is the beat frequency, i.e. the difference between the two blinking frequencies.
A cheapo 20ppm quartz watch crystal definitely doesn't drift by a second every few minutes, but it will over about about half a day at maximum error. A 5ppm one (still sub one Euro) will keep a second about every two days. A 0.5ppm TCXO can be had for about 15 Euros from Mouser and that gets you two weeks. If you have shared line power you can just use that and everything will be locked in sync forever. If you don't…
Well, yeah. I was sort of assuming that you won't use a TCXO or even just a cheapo quartz crystal, because it doesn't make a lot of sense: You've now thrown money at something that will relatively quickly desync anyway.
I mean, sure, the TCXO will mean that you only start seeing a phase difference between the two after weeks instead of minutes, but what's the point of that? I you want them to be at the same phase, you'll need to sync them at some point, and you do that by using a common clock source.
So either you shell out some effort for a real solution (power line is nice, and also qualifies as a common clock source as I've predicated), or you don't. And if you don't, there's no point in using a precise-ish clock at all, and you'll likely end up with very quick desyncing.
Re: Why do some radio towers blink?
#59Related: Some wind turbines apparently only turn on their position lights when there's any aviation traffic nearby (as detected by either local transponder interrogators (possibly ADS-B receivers?) or radar)!
Radar, called Aircraft Detection Lighting Systems (ADLS). The requirements are summarized in the FAA Advisory Circular covering aviation marking and lighting.
Re: Why do some radio towers blink?
#60These beacons are also great for navigation. Aeronautical charts usually show the color/pattern of the light. You can use those as points to triangulate your position.
IIRC, light houses are marked on charts similarly. The lights have different patterns, maybe color too?? Maybe not on aeronautical charts though.