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Why do some radio towers blink?

jeffgeerling.com

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Re: Why do some radio towers blink?

#121

Post by nucleardog »

noir_lord wrote: post #119
ssl-3 wrote: post #98

Earlier quoted context omitted.

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 -- on…

> How does one connect a lamp to 3-phase power? You typically connect 1/3 of lamps on one phase, one third on another and so on. In the UK we use a 230V single phase system for most things (industrial/commercial often use 400V) (if all three phases are in use it's 400V - you may see it as 415V but we harmonised with Europe to 400V) so lighting expects that 230V anyway, you still have a common ground, you just run the…

> We have standard colors for this as well (as do most jurisdictions), neutral is always blue but the phases are Brown, Black and Grey

Never even thought about the fact that different regions may have different colour standards. This explains some of the power cables I've torn apart over the years and the strange colours I found inside!

> When I trained as an industrial electrician they where different colors, they changed in 2006 so that just makes me feel old (used to be Red, Yellow, Blue with Black for Neutral).

Making a mental note of that one... a black neutral would be a nasty surprise coming from North America.

Re: Why do some radio towers blink?

#122

Post by noir_lord »

nucleardog wrote: post #121
noir_lord wrote: post #119

Earlier quoted context omitted.

> How does one connect a lamp to 3-phase power? You typically connect 1/3 of lamps on one phase, one third on another and so on. In the UK we use a 230V single phase system for most things (industrial/commercial often use 400V) (if all three phases are in use it's 400V - you may see it as 415V but we harmonised with Europe to 400V) so lighting expects that 230V anyway, you still have a common ground, you just run the…

> We have standard colors for this as well (as do most jurisdictions), neutral is always blue but the phases are Brown, Black and Grey Never even thought about the fact that different regions may have different colour standards. This explains some of the power cables I've torn apart over the years and the strange colours I found inside! > When I trained as an industrial electrician they where different colors, they c…

Indeed, half my house is blue/brown, the other half is black/red since reg changes where grandfathered in and the wiring has been added to (some places clearly by a knowledgeable individual others..not so much).

I spent the first day after we bought it and moved in going around with a screw driver, side cutters a notepad and enough swearing to make a pirate with Tourette’s blush.

It’ll need a full rewire at some point, while I can do it myself to a commercial standard our regs require a currently qualified electrician sign off (mine expired many years ago) so I’ll just pay someone to do the lot.

It’s annoying but I’ve seen enough horror shows to see why it’s nescessary.

Re: Why do some radio towers blink?

#123

Post by MisterTea »

kcplate wrote: post #96
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.

I imagine that a properly constructed ghillie suit covered with chain link fencing, barbed wire, no trespassing signs and a blinking red light might go undetected...

Re: Why do some radio towers blink?

#124

Post by hylaride »

noir_lord wrote: post #118
hylaride wrote: post #114

Earlier quoted context omitted.

Back in the analog TV days, I could see the flicker on the 50hz PAL/SECAM signals whenever I visited Europe, especially when the screen was white and in my peripheral vision. I always wondered why it didn't drive everybody nuts, but then I got used to it. I did always wonder if there was a way they could have eliminated that (maybe they did in more expensive TVs that fired off at double the reference signal and not i…

simple answer is grid frequency in europe is 50hz, in the US and Canada it's 60hz. Early TV's synchronised to the grid frequency (and drew the entire screen on each cycle) - also remember TV's where analogue to start with (and operated at large voltages/transformers) so if they didn't sync with the grid electrical noise becomes a big problem with the power supply. In monitor terms it reduced jitter.

Yeah, I knew why. :-)

My brain immediately went into "solving" mode, though.

Re: Why do some radio towers blink?

#125

Post by anikom15 »

hylaride wrote: post #114
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.

Back in the analog TV days, I could see the flicker on the 50hz PAL/SECAM signals whenever I visited Europe, especially when the screen was white and in my peripheral vision. I always wondered why it didn't drive everybody nuts, but then I got used to it. I did always wonder if there was a way they could have eliminated that (maybe they did in more expensive TVs that fired off at double the reference signal and not i…

The 100 Hz TVs weren’t that common and had other issues. They weren’t strictly superior. TVs were supposed to use a different set of phosphors for 50 Hz that were less flickery at 60 Hz but in practice I don’t know if tube producers bothered to have different sets for the different markets.

Re: Why do some radio towers blink?

#126

Post by pizzalife »

mikestew wrote: post #76
pizzalife wrote: post #31

Earlier quoted context omitted.

Yes, reading transcripts is a terrible way of ingesting information in my opinion.

Then go watch the video? What are you asking for here?

I'm not asking for anything. Just commenting that transcripts of videos make for bad blog posts. I'm not interested in watching the video.

Re: Why do some radio towers blink?

#127

Post by barbazoo »

gorgoiler wrote: post #41
barbazoo wrote: post #14

These 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.

You have brought back to me memories from 30+ years ago, playing Microsoft flight simulator, trying to triangulate my position using VOR beacons as quickly as possible before my aircraft had moved so far on that I was no longer anywhere near my triangulated position, hah!

I never appreciated how realistic FS was until I started studying for the navigation part of my PPL. I flew a 172 too so the instruments felt very similar.

Re: Why do some radio towers blink?

#128

Post by mikestew »

pizzalife wrote: post #126
mikestew wrote: post #76

Earlier quoted context omitted.

Then go watch the video? What are you asking for here?

I'm not asking for anything. Just commenting that transcripts of videos make for bad blog posts. I'm not interested in watching the video.

Ah, not interested in the video, that clarifies it, thanks.

Re: Why do some radio towers blink?

#129

Post by quickthrowman »

wtallis wrote: post #93
marcosdumay wrote: post #84

Earlier quoted context omitted.

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…

There are no light fixtures that use three-phase power. At least that’s my belief, as I’ve never heard of one or seen one and I’ve been working in the electrical industry for almost a decade. You could theoretically arrange three lampholders like a delta or wye transformer [0] and connect a phase to each one and all three lamps will be lit, but the lampholders will be energized, so make sure to wear voltage-rated gloves when changing out the lamps ;) This is how three-phase resistive heaters are wired, the drop in ampacity and large resistive heating loads make it worth using three phase since ampacity is 1.73 times lower than it would be on a three-phase circuit than it would be at the same voltage as a single-phase circuit.

In the US, there are 208V single-phase and 480V single-phase lights that use two of the three phases. In practice, indoor lighting is either 277V (line to neutral on a 480V service) or 120V (line to neutral on a 208V service). Most commercial LED fixtures can use any voltage between 120V to 277V single-phase.

480V single phase is used for some pole lighting with long runs of conductors to handle voltage drop. Anything over 277V has to be elevated at least 22 feet off the ground per the NEC.

[0] https://en.wikipedia.org/wiki/Delta–wye_transformer

Re: Why do some radio towers blink?

#130

Post by kcplate »

MisterTea wrote: post #123
kcplate wrote: post #96

Earlier quoted context omitted.

> 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.

I imagine that a properly constructed ghillie suit covered with chain link fencing, barbed wire, no trespassing signs and a blinking red light might go undetected...

In that case I guess I wouldn’t have an opinion
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