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Why do some radio towers blink?

jeffgeerling.com

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Re: Why do some radio towers blink?

#91

Post by estimator7292 »

mulmen wrote: post #37
scblock wrote: post #25

Earlier quoted context omitted.

It's so pilots see the entire wind farm as a single entity and can interpret what they see and understand the extent of the wind farm easily. There is a pretty good study you can read on this: https://www.airporttech.tc.faa.gov/DesktopModules/EasyDNNNew... As to community impact, radar-activated lighting is an approach that is being used in places this is a concern. It allows the lights to remain off unless there is…

Does it have to be radar? Can it use ADS-B?

This is a safety measure. You can't rely on ALL aircraft having functional (or installed) transponders. You must actively sense incoming craft because they don't always politely announce themselves.

Re: Why do some radio towers blink?

#92

Post by fipar »

mr_toad wrote: post #50
Terr_ wrote: post #32

> 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…

I can’t imagine why they’d need a hazmat suit either. It’s probably just protection from the cold.

Seems to be needed only for old towers:

> Tower painting has changed a lot over the years. The older towers have lead in them. 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?

Re: Why do some radio towers blink?

#93

Post by wtallis »

marcosdumay wrote: post #84
genter wrote: post #82

Earlier quoted context omitted.

I was told that you want lights on all 3 phases so that you can see spinning things spin. If the lights are on single phase, they will dim 120 times a second, and the strobe effect can cause spinning things to appear stationary. With 3 phase, at least 1/3 of the lights are lit all the time.

That's a valid reason too. In an industrial environment full of rotating machines, thinking something is stationary because it's on the grid's natural frequency can be lethal. It's way less of a problem with modern machinery, and leds will blink in uncorrelated phases in a frequency that is different from the grid's anyway.

For residential lighting running off a single-phase supply, there are some annoying LED bulbs with simple half-wave rectification that strobe at the grid frequency with less than a 50% duty cycle (often seen with bulbs emulating vintage exposed-filament bulbs with no frosted glass). It would be interesting to see how much less annoying that kind of flicker is when you have a three-phase supply to a light fixture, so that at least one set of LEDs was illuminated at all times.

Re: Why do some radio towers blink?

#95

Post by CableNinja »

dylan604 wrote: post #70
WalterBright wrote: post #67

Earlier quoted context omitted.

I know. But when I was programming LEDs for my single board computer, I found that blinking the LEDs used a lot less power. If the blink rate was fast enough, your eye did not distinguish that from the LED being on 100% of the time. I don't know if battery powered devices generally use that trick or not.

all dimmable LEDs use blinking, but interesting case for your suggestion for an even more efficient use of a "steady" LED. what blink frequency did you use to keep it from being visible to the eye? did it not dim the overall brightness to a meter? early LEDs were atrocious with their slow blink rates that quickly scanning across them could see it, but even more noticeable if you pointed your camera at them. now, they…

You only need about 40hz to make it seem on all the time, TVs (before 2020, maybe earlier) only did 25hz-ish. You can actually play pretty ridiculous tricks on the brain if you know this. For example, in VR, in a large enough room, you can slightly alter the angle the player sees inbetween frames. This alteration makes the brain think youre slightly offset from where it thinks you should actually be. This allows you to cause a person to walk in a circle irl, while they think they are walking in a straight line. Unfortunately only works up to a threshold of change, before the brain starts getting confused and causss the user motion sickness.

Re: Why do some radio towers blink?

#96

Post by kcplate »

Terr_ wrote: post #32

> 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…

> If you see someone up in a tall tower wearing a ghillie suit

My first thought would be “that might be the dumbest sniper I have ever seen”…while I was taking cover, because even if they are dumb, they might still be a capable marksman.

Re: Why do some radio towers blink?

#97

Post by dylan604 »

CableNinja wrote: post #95
dylan604 wrote: post #70

Earlier quoted context omitted.

all dimmable LEDs use blinking, but interesting case for your suggestion for an even more efficient use of a "steady" LED. what blink frequency did you use to keep it from being visible to the eye? did it not dim the overall brightness to a meter? early LEDs were atrocious with their slow blink rates that quickly scanning across them could see it, but even more noticeable if you pointed your camera at them. now, they…

You only need about 40hz to make it seem on all the time, TVs (before 2020, maybe earlier) only did 25hz-ish. You can actually play pretty ridiculous tricks on the brain if you know this. For example, in VR, in a large enough room, you can slightly alter the angle the player sees inbetween frames. This alteration makes the brain think youre slightly offset from where it thinks you should actually be. This allows you…

>TVs (before 2020, maybe earlier) only did 25hz-ish

tell me your European without telling me.

> You can actually play pretty ridiculous tricks on the brain if you know this.

I do random persistence of vision tricks all the time. I can see flickering in cheap CFLs or old tubes with bad ballast, and now with LEDs seeing the cheaper controllers with slow blink rates. Once you know how, the brain is a dumb rube waiting to be tricked. Only believe half of what you hear and none of what you see.

Re: Why do some radio towers blink?

#98

Post by ssl-3 »

genter wrote: post #82
xenadu02 wrote: post #36

Earlier quoted context omitted.

This is best practice for anyone who uses three phase power. A machine shop should connect 1/3 of their lights to each phase so it is immediately obvious if a phase gets dropped. Lots of equipment will suffer on two of three phases but with lower performance or even damage.

I was told that you want lights on all 3 phases so that you can see spinning things spin. If the lights are on single phase, they will dim 120 times a second, and the strobe effect can cause spinning things to appear stationary. With 3 phase, at least 1/3 of the lights are lit all the time.

How did that work, do you suppose?

How does one connect a lamp to 3-phase power?

Are/were there 3-phase fluorescent tubes available?

Or are we relying on the spinny-thing that is to be observed to somehow be illuminated by all three phases, with three lamps or fixtures, simultaneously? Without such malarcky as shadows or inverse-square to muddy our vision?

Or maybe a multiplicity of single fixtures with 3 tubes -- one tube per each phase?

And even then: Doesn't it still strobe somewhat at (50*3*2)=300 or (60*3*2)=360Hz, instead of the 100- or 120-Hz that a shop lit by a single phase might provide?

(LEDs are out-of-scope of this question, of course: Line-voltage LED lamps can have integrated electronics and can therefore have diode elements that are driven by things that approach [or even achieve] DC, which changes the rules.

And, of course: Incandescent lamps have enough persistence that stroboscopic effects are generally not an issue with a human eye.)

Re: Why do some radio towers blink?

#99

Post by mjevans »

geerlingguy wrote: post #68
scblock wrote: post #65

Earlier quoted context omitted.

Definitely GPS. Other methods have been used in the past--I remember reading operating reports from a wind farm nearly 20 years ago that slowly brought all its lights in line with each other over several months--but these days you can buy mainstream lighting with the GNSS receiver built in from a number of suppliers. They make it easy. For wind farm use most also have an external input for ADLS triggers, though that…

Hmm... maybe I could build a 1pps GPSDO based on light flashes from nearby towers, then. No need for my own GPS antenna!

You'd probably have better timekeeping from a reasonably connected Pi with a common NTP daemon (take your pick, some are easier to configure / query), and a realtime-ish thread to emit your PPS signal on a GPIO or similar.

Probably more robust than line of sight, and able to pool with other NTP servers in your home-lab (and beyond).

Re: Why do some radio towers blink?

#100

Post by mjevans »

estimator7292 wrote: post #90
geerlingguy wrote: post #56

Earlier quoted context omitted.

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.

You can have each tower derive a perfectly stable 1Hz signal from the mains, but you have no way to synchronize those signals. Each tower's 'tick' starts at a random point in the 60Hz cycle. You need an external, dedicated channel for this. You either synchronize with signals sent between towers or with a global signal from somewhere else (space). GPS broadcasts atomic time references for free, so everyone just uses…

Just like a freeway, public good and public benefit are things government should be doing well. (We the people, for us the people)
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