#1
Hey, so in my university physics course, my lab instructor told me that it's possible to tune a guitar by holding it near an old tube television. Apparently, when the guitar is in tune, you will see a standing wave (like a sine wave) on the screen when you pick the "first chord." (I assume he meant the E string, but I'm not sure). If the guitar is slightly sharp or slightly flat, you should see the same wave, but moving either to the left or right.

My instructor also said that it works better in Europe, because the frequency at which the screen refreshes is closer to one of the open strings in a guitar tuned to standard tuning. But he did say that it would work in North America if you knew what frequency the guitar had to be tuned to.

Does anyone know what frequency this is, and what note it corresponds to? Also, is there a certain way you have to hold the guitar, in relation to the television? How close does it need to be? Do you have to use an amplifier, or will an acoustic guitar do the same? My instructor didn't know the answers to any of these questions; he just said that he had seen it done before.
#2
Yes. It's 67.9843 Hz to the 5th power. Divide by pi and figure for the tangent of 17. Turn your head to the North, cough 3 times, spit on the ground and fart. Your frequency will be spelled out in the clouds and your guitar is now in-tune.
#3
Quote by KG6_Steven
Yes. It's 67.9843 Hz to the 5th power. Divide by pi and figure for the tangent of 17. Turn your head to the North, cough 3 times, spit on the ground and fart. Your frequency will be spelled out in the clouds and your guitar is now in-tune.

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#5
1st chord probably means A which is at 440. I've actually seen tuners that look sort of like they work off the principle you're describing, but I honestly don't know. Very interesting, though. I'm hoping this really does work.
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#6
Quote by KG6_Steven
Yes. It's 67.9843 Hz to the 5th power. Divide by pi and figure for the tangent of 17. Turn your head to the North, cough 3 times, spit on the ground and fart. Your frequency will be spelled out in the clouds and your guitar is now in-tune.


Well, at least you made me laugh
#7
Quote by KG6_Steven
Yes. It's 67.9843 Hz to the 5th power. Divide by pi and figure for the tangent of 17. Turn your head to the North, cough 3 times, spit on the ground and fart. Your frequency will be spelled out in the clouds and your guitar is now in-tune.

Just said this to a few of my housemates...hilarious.
#8
NTSC has got a 60hz refresh rate
PAL has got a 50hz refresh rate

if you're tuning to A4=440hz then your low E string is 82.4hz

three frets up the G is 98hz (close to two times 50hz = 100hz), though G# is 103.8hz
I don't have a TV but I think if you played a G in front of a european TV (with a CRT, no lcd or plasma stuff) you'd see a relatively still wave on the string (or possibly more like 2 waves superimposed on each other, one upside down to the other)

the low B on a 7string is 61.7hz
the lowest B on a regular guitar is 123.5hz, you might be able to see that with a standing wave on an american tv set


so no, you're not going to a perfect tuning form this


get yourself one of http://accessories.musiciansfriend.com/product/Planet-Waves-SOS-Strobe-Pick-Tuner?sku=210066
#9
Oh don't worry, I don't plan on actually tuning my guitar like this; I just thought it would be neat to see the wave. But thanks for the info.
#10
Supply freq is 50Hz in parts of Europe and 60Hz in USA,
But I guess the teacher is referring to the refresh or frames per sec frequency that the CRO in the tv scans at.
Ever seen the spokes on those wagon wheels rotating slowly backwards in the old westerns while the wagon races forward? that's down to a similar reason.
#11
As an electronics technician, I can assure you this method is totally ficticious.

About the only thing you'll see on an old CRT set is a colorful rainbow pattern if you bring the magnetic pickups too close to the screen. This will also work on any old CRT monitor. The stronger the magnet, the stronger the effect. Do be careful with this 'trick', however. Some TVs and monitors use a shadow mask. The shadow mask is a thin screen located just behind the front of the CRT glass. If the magnet is too strong, the mask can be permanently bent. If the TV has been on for a long time, the mask will be a lot warmer and more easily damaged. The magnets from a hard drive, for example, are very strong and could easily damage the mask. The magnet can also temporarily magnetize the screen, leaving the 'rainbow' effect. Turning off the set and then turning it back on will degause the screen and it should go away after a couple of power cycles.

However, using an old TV to tune a guitar is impossible. The guitar would have to generate some sort of RF (Radio Frequency) field, which it does not. The signals generated by the pickups are extremely weak and in the audio frequency range, hence the reason why you hear your guitar when it's plugged into an amp, or even when it's not. If the guitar isn't plugged into anything, we have the additional problem of the pickups being an open circuit. And before someone can suggest it - no, this won't even work with active pickups. Nice try. The best thing to use for tuning your guitar is your ear, or better yet, a tuner. If you live in Boston or Long Island, that might be a tuna...
#12
If you're really stuck - depending on where you live you can use your dial tone.

As for the standing wave ask your professor if he has ever done it or is he speaking hypothetically. I tried it with my tube tv and got no change whatsoever. Perhaps you need to plug your guitar into some kind of device first that will send the right kind of signal to interfere with the TV signal.

I have seen the waves you talk about. They come across the screen and stand still. Sometimes they move slowly. Sometimes faster. It used to happen when the lady in the flat next door would use some of her kitchen appliances (I'm not sure which ones). - Usually in the middle of my favourite programme.
Si
#13
Quote by KG6_Steven
Yes. It's 67.9843 Hz to the 5th power. Divide by pi and figure for the tangent of 17. Turn your head to the North, cough 3 times, spit on the ground and fart. Your frequency will be spelled out in the clouds and your guitar is now in-tune.



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#14
Quote by 20Tigers
If you're really stuck - depending on where you live you can use your dial tone.

As for the standing wave ask your professor if he has ever done it or is he speaking hypothetically. I tried it with my tube tv and got no change whatsoever. Perhaps you need to plug your guitar into some kind of device first that will send the right kind of signal to interfere with the TV signal.

I have seen the waves you talk about. They come across the screen and stand still. Sometimes they move slowly. Sometimes faster. It used to happen when the lady in the flat next door would use some of her kitchen appliances (I'm not sure which ones). - Usually in the middle of my favourite programme.



My professor said that he had seen it done, but he is something of a crack-job so I wasn't sure whether to believe him. Maybe whoever he saw did have some kind of signal converter, but I'm not sure.

As for the tuner, I am capable of tuning my guitar by ear. I just wanted to know whether I could produce waves on my TV set with my guitar, because I think it would be a cool experiment.
#15
Quote by KG6_Steven
As an electronics technician, I can assure you this method is totally ficticious.

About the only thing you'll see on an old CRT set is a colorful rainbow pattern if you bring the magnetic pickups too close to the screen. This will also work on any old CRT monitor. The stronger the magnet, the stronger the effect. Do be careful with this 'trick', however. Some TVs and monitors use a shadow mask. The shadow mask is a thin screen located just behind the front of the CRT glass. If the magnet is too strong, the mask can be permanently bent. If the TV has been on for a long time, the mask will be a lot warmer and more easily damaged. The magnets from a hard drive, for example, are very strong and could easily damage the mask. The magnet can also temporarily magnetize the screen, leaving the 'rainbow' effect. Turning off the set and then turning it back on will degause the screen and it should go away after a couple of power cycles.

However, using an old TV to tune a guitar is impossible. The guitar would have to generate some sort of RF (Radio Frequency) field, which it does not. The signals generated by the pickups are extremely weak and in the audio frequency range, hence the reason why you hear your guitar when it's plugged into an amp, or even when it's not. If the guitar isn't plugged into anything, we have the additional problem of the pickups being an open circuit. And before someone can suggest it - no, this won't even work with active pickups. Nice try. The best thing to use for tuning your guitar is your ear, or better yet, a tuner. If you live in Boston or Long Island, that might be a tuna...

I think what his prof was getting at is more of a strobe light effect due to the refresh rate of the TV