Just wondering.
A tightly-drawn violin string goes up in acoustic pitch the tighter it is tuned.
Just wondering.
A tightly-drawn violin string goes up in acoustic pitch the tighter it is tuned.
What if a strong wire antenna is brought to an extreme degree of tautness? Does its resonant RF frequency increase?
Trouble is, even if it worked, it would not solve any problems for Part 15 medium wave.
But maybe, again depending on whether tautness has any affect, there’s a counter-method of tuning lower. A string bass has a thicker string that tends to be helical. We have talked about helical antennas. Maybe this concept brings a new way of viewing their potential.
Tight Grip
Well for starters, a guitar string is resonating a a MUCH lower frequency. Also as you tune a guitar string, your not only giving the string more tautness, but also making it shorter as you turn the tuning key. As you turn the tuning key, the string wraps around the tuning key stud.
And just like a wire antenna for radio, the shorter it is, the higher wavelength of resonance.
RFB
I Agree!
I Agree!
Taut-a-taut
RFB is right, but there are a couple things to think about:
1) Tautness is simply a bi-product in an antenna situation. The length is the key, not how taut it is, except mechanically. Stringed instrument strings are meant to be taut. Stretching them also changes the diameter. In the antenna situation, it could slightly alter the gauge diameter, but I doubt it would be enough to alter skin effect appreciably.
2) Sound waves are different than EMF waves. There is a correlation, but it happens during electro-mechanical conversion and the modulation process. IOW, you can’t pick up sound waves on a radio without going through that processing at both ends (opposite each other).
Another note
Another thing to take note of is the different sizes of the guitar strings for each “home” note/frequency.
The lower notes have larger gauge and the higher notes have smaller gauge, following the same principles for EM emission at different wavelengths…the lower the wavelength..the larger and longer the wire/element, the higher wavelength, the smaller the wire/element and shorter.
RFB
Looking For Haystacks
It appeals to me to attempt a better understanding of the parallel physics of RF electronics and electro-acoustics, because the two types of resonances and waves are curious for the very reason that they are different, yet in some ways the same.
For example, I am endlessly puzzled by the fact that the extra-long wavelengths of low audio frequencies can be generated by devices that are relatively small in relation to those wavelengths. It seems like there ought to be an analogy in RF, whereby long wavelengths can be resonated by smaller devices.
I have seen only one mistake in what was said up above….. tightening the string on a musical instrument does not make the string shorter. If it did, the neck of the guitar or violin would start bending and maybe break.
Nodes and Resonance
The analogy between RF and strings can be carried further. A string will only support resonant waves which fit between the two ends which are constrained so there is no movement. These wavelengths are such that the mechanical motion at the ends are zero. This would be 1/2 wavelength, 1, 1 1/2, and so on as long as the wave fits so there is no motion at the ends.
Same thing for antennas except the constraints are different. At the end of the antenna the current has to be zero so only wavelengths with zero current at the end of the antenna will resonate. It is also possible to establish resonance with the ends of the antenna shorted such that the voltage has to be zero. An operating antenna could be shorted to ground at a voltage node without affecting the signal. This is handy at VHF and above where the support for the antenna can be conductive between the radiator and the mast which provides mechanical strength plus a DC path to the mast.
Neil
Not Taught – Get Loose
Maybe try the wet approach using that SALT WATER antenna posted here some time ago.
Not a mistake
Carl…the guitar string DOES in fact get shorter as you turn the tuning key. You can perform a test to that fact by simply loosening the string on a guitar till it is sagging, and then re-tune the string and note the string becomes taut.
If the string is not getting shorter between the bridge on the body of the guitar (ie one end) and the other end that wraps around the tuning stud…where does that extra length of the string go???
RFB
An example experiment
Take a rubber band. Cut it so it is a single length (ie not a loop). Wrap a couple of turns around a pencil at one end, and do the same at the other end.
Now as you pull the two pencils apart, and pluck the rubber band, you will note that the tone produced does increase a little….BUT…now turn the pencils so that the rubber band gets tighter, and adds more rubber band onto the ends of the pencils…note how FAST the tone increases in pitch compared to just stretching it.
So quizzzz…..what are you doing to the rubber band to make it increase pitch?
Your doing two things….tightening the tension AND making the rubber band shorter by turning the pencils to wrap more of the rubber band around the ends of the pencil…THAT is making the rubber band shorter between the two pencils AND making it tighter between those two pencils.
RFB
Guess it Depends
Guess it depends on what the definition of shorter is.
Neil
Psuedo Science
Plans are to build a ten foot wire antenna with a crank on the top to tighten that wire until it almost snaps. Then we’ll sell it on e-bay.
Slinky Stick
There is an antenna on ebay called a “Slinky Antenna” and works beautifully for LW/MW and SW DX’ing. It literally is a slinky, allowed to stretch from a hanging point and fed with a single wire attached to the whip antenna on a receiver with a clip.
Designed for those with limited space or those living in apartments or where large outdoor wire antennas are not practical, this “Slinky” antenna is one SLICK puppy and so easy to make!
Just search on ebay’s search bar for “slinky antenna” and there are quite a few results for all types of slinky antennas!
RFB
Inspired By Pet Rock Grounding Kit
The slinky antenna sounds like it could make an attractive way to have a neat indoor antenna. Would it be helical?
Then I had a brainstorm idea. As you know, some products are required to have warning labels the way cigarettes and alcohol do. But can we add our own creative warning labels? I want to add a very alarming warning sticker on the “crank” antenna: THIS PRODUCT HAS BEEN LINKED TO EXTREME EXCITEMENT LEADING TO OUTBURSTS OF FEELING WELL.
LOL!!
LOL (laugh Out Loud) the slinky antenna might not be a bad idea at all, the creative warning joke i thought was funny!!! 🙂