Gravitational Engineering - What We Can Do Now

LB,

I observed an apparently non-screenable coupling between two quartz xtals measured about 20x7x0.5 mm each, their resonance freq was 150 kHz (obviously a transverse mode freq, we'd better use longitudinal modes for higher freq's). Those were some very old stuff from the days when xtals were big. The signal in the output was noticeable on a simple oscilloscope at 0.05 mV/div (no special preamps used!) till about 10 cm distance when the "transmitter" xtal was driven by 5 V TTL oscillator circuit. Then I didn't think of measuring the speed or phase of the signal, I just remember the fact for it's apparent peculiarity.

Anyway, those things cannot be too expensive. Even if we'd have them built to order, that'd be within a few k$ for truly big ones like 10 cm side cubes. The best place to find some very big and old xtals is to look at some polytechnical museums or old labs with piles of ancient tech stuff. All the setup might turn up as cheap as free.

Apart from that idea, we might think of measuring speed of some near astronomical gravity perturbations. I think of measuring the tidal force variations back from the Sun or Moon across the Earth body. Those tidal forces are essentially the dipole component of field, so they have a good chance to be verry fassst <img src=icon_smile_wink.gif border=0 align=middle>.
(though i have a remote suspicion that gravity variations can themselves be kinda "redshifted" or smoothed out within massive medium)

AB,

What type of shielding schemes did you use? (Seems like I remember you mentioning the known presence of some acoustical coupling back when you first brought this up.)

Do you, perhaps, remember how long it took the receiver crystal to build up a detectable output after the transmitter was turned on?

Regards,
LB

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>What type of shielding schemes did you use? (Seems like I remember you mentioning the known presence of some acoustical coupling back when you first brought this up.)<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>I used normal things that an electronic guy uses - copper folio for electric part and heavy porous rubber for acoustical part and naturally I first removed the "receiver" xtal from the board where the "transmitter" was mounted, just to be sure. Then I tried to put in between whatever was lying around, just for the kicks. Then I checked the acoustic field with some top quality ceramic sensors (the would-be hydrophones) lying around and found nothing, then I dipped the "transmitter" xtal into a water tank with hydrophone in it and then found a signal a few dB above the background noise.
But the problem with xtals is their crazy Q-factor, one can never be sure, so modulating the signal is a must when trying to measure the signal speed and use of charge-sensitive preamps is advisable.
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>Do you, perhaps, remember how long it took the receiver crystal to build up a detectable output after the transmitter was turned on?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
Well, I didn't notice any macroscopic delays. But then I never checked for that specifically. I just moved it around and never felt a delay in response, but that's only about ten millisecond range. Sorry.

What specific equipment would be needed to test this? This sounds very promising. It seems simple, that is always elegant. Less things to mess up. - MV

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[MV]What specific equipment would be needed to test this?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote> Before any real experiment is attempted, a "proof of concept" kind of setup can be assembled from readily available parts.
I'd advise the following -

1. find two 3.58 MHz xtals from old colour TVs, the older the TV - the bigger those xtals are;

2. assemble a simplest oscillator circuit around that xtal, ensuring that high enough AC current is flowing through the xtal, which means that you'd better use the series resonance mode (where xtal impedance is close to 0);

3. use a good oscilloscope with about 10 <img src=icon_mu.gif border=0 align=middle>V/div sensitivity limit, connect the "receiver" xtal directly to the oscilloscope probe and fix it there somehow (use some scotch tape or whatever) and then poke the probe around the "transmitter". Don't forget to adjust the oscillator freq for the max output in the receiver.

If all succesful, proceed with looking for more special xtals, or order special ones, resonance frequencies should be about 10 MHz at least.
For a real experiment later you'd a need signal generator capable to produce about 100 V/ns fronts in pulses of about 100 V amplitude and a good instrumental preamp with current (rather than voltage) pickup and bandwidth at least 10 times wider than resonance freq of your xtals, the same bandwidth requirements apply to your oscilloscope. Acoustic decoupling at above 10 MHz is not a problem; and furthermore, you're not going to measure the steady oscillations in the receiver but rather the time delay in response signal attack, and that time should readily tell you the signal velocity which is very different for acoustic coupling.

I find it somewhat humorous that old tv parts could help determing the SOG. It sounds wacky enough that it could work. It would also renew the garage inventor in American folklore. Someone head over to Sammy's Used Appliance store and make it happen. (send me a schematic, i have all of that equipment except the xtals. I will build this!) - MV