Results

Just finished an acoustic test of the EMDrive V3 and got interesting results:

Neither my milligram scale nor the interferometer with its relatively heavy table was able to detect any force due to noise.
I tried to pick up some force by attaching an electret capsule to the cavity, modulating the output power with a low frequency and looking into the acoustic spectrum (with HDSDR) - and voilà, there are some results.
Of course, this quick test doesn´t prove that the force is directional and not just a vibration.
But it shows that the peak only occurs around the resonant frequency of 24100 MHz for which the cavity was designed - and stops when no modulation is applied or the frequency is too much off the center frequency.
What I didn´t check yet is if the picked up signal is just the EMI of the transceiver. I´ll check it later of course - anyway to avoid trolls to call my science "bad" - more tests will follow

Additional information: The peak is not at the modulation frequency (76 Hz) but in the kHz range - it changes when I change the modulation frequency. Is it an alias effect or maybe a harmonic on the mechanical resonance frequency - I´ll have to take a closer look. The HDSDR software is usually used with an radio receiver so the frequency display under the waterfall was wrong (so I blacked it out). I´ll need to make the correct settings to see the correct audio frequency of a peak - I´ll do it in the next post.
Anyway this result is just preliminary, I posted quickly what I just did - I´ll check if it´s also happening when the electret capsule is not attached to the cavity but just nearby.

Discussions

zephir wrote 05/14/2016 at 12:14

Can you hear some acoustic noise or pitch during run of the device? The human ears are quite sensitive detector at times...

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Paul Kocyla wrote 05/14/2016 at 17:26

No, nothing with the ear. Just a weak signal through the microphone. I even needed to sample it through SDR software which makes an FFT and integrates the signal to make it visible. But it was there :)

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willemstaal wrote 05/17/2016 at 14:25

Try to use a old piezo speaker like the ones they use for christal radios . these things are sensitive enoegh.

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Michelle wrote 02/15/2016 at 18:03

Hi Paul,

I think your doing very nice work and are to be congratulated on it. What I found interesting is the orange area on your graph where I think can be seen your resonance. In my testing at 2.45GHz the resonances were not identical on either side of the center Fo. Traveling up from center, the higher frequency cutoff of the chamber degraded the and caused a faster fall out of resonance. I wonder why we don't see that same effect here and see almost a mirror image?

SeeShell (Drive Builder

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Paul Kocyla wrote 02/16/2016 at 13:51

Thanx. The two identical lines are the peaks of the acoustic pick up from the cavity, not the driving frequency.
I modulated the RF power on/off with about 80 Hz and looked if the cavity setup will mechanically resonate at its natural ringing frequency. The acoutic measurement seemed more sensitive than the balance scale as I only have 100mW of RF.
I used an electret capsule to measure mechanical vibrations, so the peaks show the vibration frequency - which has been around 2.7 kHz.
The RF driving frequency for the cavity was fixed to 23890 MHz in this experiment.
The spectrum software I used for measuring the vibrations requires an I/Q - Signal, because it´s originally for radio reception. If only a real signal is put in, like in my case an electret microphone, the spectrum is mirrored around the center (DC, 0Hz a the big orange line), that´s what happens when you perform a fourier transformation for a signal without a complex component.
The peaks degrade when I detune the driving frequency about +/- 30 MHz.
Take a look into the next post. I put some more mass onto the cavity to look if the mechanical resonance frequency will be lower - it was :)
Thanx for your comment - and congratulations for your build, too. Good work!

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Michelle wrote 02/16/2016 at 17:29

Thanks Paul. It makes sense now as to what I was seeing. It is wise to detail out all the internal and external reactions the DUT might see. From external thermals, air currents, Lorentz, and yes even vibration harmonics. It is one small step, isn't it?

Thanks for the kuddos on my build.

Shell

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IslandPlaya wrote 02/15/2016 at 11:31

Some commentators have mentioned that you are just messing around having a laugh by not labeling the axes of your graphs and such like. They suggest that maybe you are not entirely serious in your investigations of claimed anomalous force produced by this sort of device.

Have you or will you address this concern in future tests?

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Paul Kocyla wrote 02/15/2016 at 16:59

I´m not doing the project to satisfy any internet community - I am doing it for personal passion. If they want to critisize me, they should first provide the results of their work - no one of these kind of commenters ever did.
From my experience the most incopetent people are the first to bark at those who actually DO something.

I explained the reason for not labeling the axes at least twice, so here I´ll do it again:
The ADC values had offsets, so the displayed phase angle won´t be correct, that´s the reason I didn´t display them before having eliminated the offset.
Anyway the phase information is visible in the graph.
I also described which axis displays which signal. Some people just don´t read or just want to throw some negative comment.

I am open to constructive criticism - but some stupid sarcastic comments or trolling from people who just fart into their sofa have no value for me.

However there are many great people leaving great comments who helped me a lot in progressing with that project. Many thanx to them!

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pomezi wrote 02/14/2016 at 05:47

Apparently, some writers have claimed the Emdrive's anomalous force or thrust is the result of Lorentz force interactions. (http://arxiv.org/abs/1510.07752).

In commenting on your test, one of the authors noted this in a recent blog posting:

There is a direct link from the resonance to the the electret capsule signal: DC supply of the RF amplifier increases when cavity is in resonance; which in turn creates EMI to change the electret capsule's output signal.

Have you or will you address this concern in future tests?

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Paul Kocyla wrote 02/14/2016 at 07:52

Yes, I am aware of this issue, had to fight with parasitic effects many times.
Anyway this experiment implies that I found the resonance frequency.
I´ll take a closer look to the VNA measurements according this frequency and will prepare a long time test on the scale - in both directions and 90° turned.

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EMDrive Cavity V3 test measurements

True mechanical oscillation

Discussions

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