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#3600 by Monomorphic on 24 Apr, 2017 20:19
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14.8V 10,000mAH lipo battery arrived. This is what will power the 30W main amplifier. This is the biggest lipo i've ever held! This is a very dangerous battery so it must be stored in a metal box and never left unattended while charging/discharging.
Beware to excessive temperature variations especially high temperatures which can cause a thermal runaway reaction that ignites a fire and consequently cause an explosion.
Normally Lithium battery aging is reduced if its storage (no charging) is made at low temperature (no freezing).
This battery has a maximum safe discharge rate of 100A. As I will be running it below 10A, I do not think overheating will be an issue. -
#3601 by Bob Woods on 25 Apr, 2017 01:26
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Hi Jamie, I'm in Charleston WV on my way home to Oregon after a wet an fulfilling March for Science in DC. I just wanted to let you and the others know that while my trip blog has been getting 30 to 50 reads a day, my blog on you is currently at 262!14.8V 10,000mAH lipo battery arrived. This is what will power the 30W main amplifier. This is the biggest lipo i've ever held! This is a very dangerous battery so it must be stored in a metal box and never left unattended while charging/discharging.
Beware to excessive temperature variations especially high temperatures which can cause a thermal runaway reaction that ignites a fire and consequently cause an explosion.
Normally Lithium battery aging is reduced if its storage (no charging) is made at low temperature (no freezing).
This battery has a maximum safe discharge rate of 100A. As I will be running it below 10A, I do not think overheating will be an issue.
Keep up your good work. -
#3602 by Mezzenile on 25 Apr, 2017 11:40
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This battery has a maximum safe discharge rate of 100A. As I will be running it below 10A, I do not think overheating will be an issue.
Fine !
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#3603 by Monomorphic on 26 Apr, 2017 13:21
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Some images I received of a build out of Poland. Jakub Jędrzejewski is using a magnetron. I'm advising him to add a circulator so he's not burning through magnetrons as quickly as I was. Looks like a nicely machined cavity with constant diameter tuning section.
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#3604 by Peter Lauwer on 26 Apr, 2017 13:48
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Some images I received of a build out of Poland. Jakub Jędrzejewski is using a magnetron. I'm advising him to add a circulator so he's not burning through magnetrons as quickly as I was. Looks like a nicely machined cavity with constant diameter tuning section.
It looks quite professionally machined. But also quite heavy. And steel bolts.
Is he going to use a torsion balance to measure forces? -
#3605 by Peter Lauwer on 26 Apr, 2017 13:52
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14.8V 10,000mAH lipo battery arrived. This is what will power the 30W main amplifier. This is the biggest lipo i've ever held! This is a very dangerous battery so it must be stored in a metal box and never left unattended while charging/discharging.
I guess I have to use a beast like that if I want to power the 3.4-3.7 GHz/20 W amplifier I bought [*]. It's supposed to consume 12 V/8.5 A.
[*] It is not functioning, though. It short circuits the power supply (>10 A) even in the OFF mode. The seller has offered to send another one if it turns out it is not functioning well: delay. -
#3606 by Peter Lauwer on 26 Apr, 2017 14:15
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In the meantime, apart from testing the RF amplifier, I have been testing some loops (picture) with a special cavity for that purpose and the Windfreak SynthNV signal source/network analyzer. I measure the transmission (S21), so I make them in pairs. Next week I'll try the loops as Zhang (2013) [1]described, see last figure.
Great device, this SynthNV, example of a measurement in the next posting where it is compared with the a measurement with a professional network analyzer.
The copperplates for the first frustum arrived, I have to buy some tools still... The electronics of the torsion balance isn't working well yet. Still lots of things to do. Could be a matter of weeks before everything is working.
I haven't bought any batteries yet. And I haven't decided/figured out how to do the communication. If the balance is opereational, I will test what the influence of 3 tiny copper wires near the torsion wire is. The USB connection will only need these wires. If there is any disturbance of the balance, I will have to use a wireless option.
[1] Hai Zhang et al., Research on Novel Loop Antenna in Microwave Cavity Measurement of Permittivity, Int. J. of Information and Electronics Engineering, Vol. 3, No. 4, July 2013.
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#3607 by Peter Lauwer on 26 Apr, 2017 14:24
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The Windfreak SynthNV network analyzer
The pictures below give an impression of how a S21 measurement with the Windfreak SynthNV network analyzer compares to one with a professional network analyzer. A cavity (length tunable, not completely the same in both measurements) of inner diameter 98 mm and two loops at both ends. The range in the measurement with the SynthNV is 2-4 GHz, that with the Agilent is 1-5 GHz.
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#3608 by Monomorphic on 26 Apr, 2017 17:05
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It looks quite professionally machined. But also quite heavy. And steel bolts.
Is he going to use a torsion balance to measure forces?
I don't know the answer to that yet. Will ask. I've also told him he will have problems with runaway thermal heating unless he finds a better way to heat sink the magnetron. -
#3609 by Monomorphic on 27 Apr, 2017 00:21
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Image showing umbilical cables as I install the Windfreak NV software on the torsional pendulum control computer. 12V 8.5A power supply, HDMI, USB spectrum analyser, and USB data.
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#3610 by ThatOtherGuy on 27 Apr, 2017 09:05
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Some images I received of a build out of Poland. Jakub Jędrzejewski is using a magnetron. I'm advising him to add a circulator so he's not burning through magnetrons as quickly as I was. Looks like a nicely machined cavity with constant diameter tuning section.
It looks quite professionally machined. But also quite heavy. And steel bolts.
Is he going to use a torsion balance to measure forces?
I just hope he won't use this method to measure forces
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#3611 by ThatOtherGuy on 27 Apr, 2017 09:46
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Image showing umbilical cables as I install the Windfreak NV software on the torsional pendulum control computer. 12V 8.5A power supply, HDMI, USB spectrum analyser, and USB data.
Sounds like you cleaned things up quite a lot ! This may help speeding up the characterization/calibration and reducing the noise and also help removing the (darn) ground loops; way to go !
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#3612 by ThatOtherGuy on 27 Apr, 2017 09:56
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In the meantime, apart from testing the RF amplifier, I have been testing some loops (picture) with a special cavity for that purpose and the Windfreak SynthNV signal source/network analyzer. I measure the transmission (S21), so I make them in pairs. Next week I'll try the loops as Zhang (2013) [1]described, see last figure.
Great device, this SynthNV, example of a measurement in the next posting where it is compared with the a measurement with a professional network analyzer.
The copperplates for the first frustum arrived, I have to buy some tools still... The electronics of the torsion balance isn't working well yet. Still lots of things to do. Could be a matter of weeks before everything is working.
I haven't bought any batteries yet. And I haven't decided/figured out how to do the communication. If the balance is opereational, I will test what the influence of 3 tiny copper wires near the torsion wire is. The USB connection will only need these wires. If there is any disturbance of the balance, I will have to use a wireless option.
[1] Hai Zhang et al., Research on Novel Loop Antenna in Microwave Cavity Measurement of Permittivity, Int. J. of Information and Electronics Engineering, Vol. 3, No. 4, July 2013.
Peter, since you're experimenting with antennas (and btw cavities), check out the attached PDF
[Edit]
Since we're at it, this other PDF may be of interest as well
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#3613 by Monomorphic on 27 Apr, 2017 15:25
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Sounds like you cleaned things up quite a lot
! This may help speeding up the characterization/calibration and reducing the noise and also help removing the (darn) ground loops; way to go !
Using the Windfreak NV signal generator/power detector has allowed me to eliminate two pre-amps and the spectrum analyser.
The signal also looks cleaner. I'm getting solid 34dBm (2.5W) into the cavity without any issues. I can also run the experiment using a single application now when before I had to use two.
Next step is to clean up the rat's nest of twisted power cables by replacing those with shielded twisted pair, and then run a series of tests at this power level and configuration before working on adding the new 30W main amplifier.
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#3614 by Peter Lauwer on 27 Apr, 2017 15:54
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In the meantime, apart from testing the RF amplifier, I have been testing some loops (picture) with a special cavity for that purpose and the Windfreak SynthNV signal source/network analyzer. I measure the transmission (S21), so I make them in pairs. Next week I'll try the loops as Zhang (2013) [1]described, see last figure.
Great device, this SynthNV, example of a measurement in the next posting where it is compared with the a measurement with a professional network analyzer.
The copperplates for the first frustum arrived, I have to buy some tools still... The electronics of the torsion balance isn't working well yet. Still lots of things to do. Could be a matter of weeks before everything is working.
I haven't bought any batteries yet. And I haven't decided/figured out how to do the communication. If the balance is opereational, I will test what the influence of 3 tiny copper wires near the torsion wire is. The USB connection will only need these wires. If there is any disturbance of the balance, I will have to use a wireless option.
[1] Hai Zhang et al., Research on Novel Loop Antenna in Microwave Cavity Measurement of Permittivity, Int. J. of Information and Electronics Engineering, Vol. 3, No. 4, July 2013.
Peter, since you're experimenting with antennas (and btw cavities), check out the attached PDF
[Edit]
Since we're at it, this other PDF may be of interest as well
Hi OtherGuy, that are VERY interesting papers. Thanks! I will study them.
Peter -
#3615 by ThatOtherGuy on 27 Apr, 2017 17:59
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@monomorphic
If you want to do it on a shoestring, consider using an RG8 shielding as a cable duct
@Pete
Not sure those may be suitable, just throwing some ideas:)
Oh and please, if you can, forgive me for sometimes spamming the forum, I'm just trying to help as much (little) as I can
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#3616 by tukatsinsky on 27 Apr, 2017 23:23
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Hi everyone! Want to introduce an interesting hypothesis about the nature of how emdrive may work, it was first proposed by Dr. Nickolay Gorkavyi(http://www.gist.us/staff.htm), former russian scientist:
he proposes that there is constant very dense field of primordial gravitational waves in the universe with a peak frequency about 2.4-2.5 GHz, which originates from a big bang. As the emdrive is an unsymmetrical cavity resonating at the same frequency as those grav. waves, it might be a crude detector of them. So there is no need for violating momentum conservation law because emdrive draws energy for it's thrust directly from this gravitational waves background and power that need for it to function is only need to make it resonating with the background. -
#3617 by graybeardsyseng on 28 Apr, 2017 01:42
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As Peter said - very interesting papers. I would mention that WRT in particular the cavity backed antennas (first paper - RongLin Li et al) , the gain patterns can get somewhat complex (a shown in several of the diagrams.). Most experimenters seem to be staying close to either Omni directional or simple gain (dipole, loop) antennas. If you go with an antenna with a more complex gain pattern there are all sorts of additional questions wrt coupling into the resonant cavity, resonate modes etc. These antennas are most frequently used in communications applications where the most important question is do they satisfy the link budget.In the meantime, apart from testing the RF amplifier, I have been testing some loops (picture) with a special cavity for that purpose and the Windfreak SynthNV signal source/network analyzer. I measure the transmission (S21), so I make them in pairs. Next week I'll try the loops as Zhang (2013) [1]described, see last figure.
Great device, this SynthNV, example of a measurement in the next posting where it is compared with the a measurement with a professional network analyzer.
The copperplates for the first frustum arrived, I have to buy some tools still... The electronics of the torsion balance isn't working well yet. Still lots of things to do. Could be a matter of weeks before everything is working.
I haven't bought any batteries yet. And I haven't decided/figured out how to do the communication. If the balance is opereational, I will test what the influence of 3 tiny copper wires near the torsion wire is. The USB connection will only need these wires. If there is any disturbance of the balance, I will have to use a wireless option.
[1] Hai Zhang et al., Research on Novel Loop Antenna in Microwave Cavity Measurement of Permittivity, Int. J. of Information and Electronics Engineering, Vol. 3, No. 4, July 2013.
Peter, since you're experimenting with antennas (and btw cavities), check out the attached PDF
[Edit]
Since we're at it, this other PDF may be of interest as well
Not trying to discourage ANY experimentation - just saying everyone using these needs to be aware of the potential impacts. In particular location, orientation and polarization should be examined; driving an emdrive cavity **may** be (much??) more sensitive (or not we just don't know yet).
graybeardsyseng
Herman
p.s. also not criticizing any cavity backed antennas. Have used various configs. in professional and amateur radio applications with great success over the decades.
graybeardsyseng. -
#3618 by graybeardsyseng on 28 Apr, 2017 02:10
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LOL are you building a bomb, by chance
?
Seriously, what about the attenuator ?
Jamie's approach to handling and using these big LiPo batteries is very prudent and well thought out. He is very right to express caution about them for others using them. In some sense they are a bit like a "bomb". Like many things in the world they are quite safe when handled correctly and quite dangerous when mis-handled or handled carelessly. Note - careless may just be because of ignorance but none the less it can be very dangerous. Learn proper handling and storage for these big batteries. There is a LOT of energy stored in there.
The only accidental fire, that occurred in engineering /program management offices, which I have witnessed in nearly 3 decades of work occurred when LiPo batteries were improperly stored. These were smallish batteries about the size of cell phone batteries and they were tossed casually into a file cabinet. Given that much chance Mr. Murphy made sure that at least one battery short circuited across a part of the file cabinet locking mechanism. Instant loud bang, smoke, flames, fire alarms and general fun and festivities for the rest of the day. OBTW - Mr. Murphy got a two-fer. The heat damaged the locking mechanism and the fire department had to chop into the cabinet with an axe.
LiPos must be charged and discharged with a purpose built charger/maintainer. Further they need to be stored in such a way as to positively PREVENT short circuiting the terminals. Special care must be taken when hooking them into a circuit - particularly multiple batteries in series or parallel configurations where sneak circuits can sometimes cause a short circuit. An accidental explosion or fire can ruin your EMdrive setup, your lab, and possibly several fingers.
DON'T take my word for this and this is NOT sufficient information or "training" on handling large lipo. Google is your friend. . . or Bing or whatever - research - learn - stay safe.
Again - not saying don't use LiPos - I use them quite a bit myself - just insure you know what you are doing and do it right.
Safety Rant Off - sorry if this rant ran on too long.
Herman
Graybeardsyseng
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#3619 by Monomorphic on 28 Apr, 2017 02:25
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All power cables have been replaced with shielded twisted pair. I also made generous use of ferrites. Looks nice and clean!
The signal also looks cleaner. I'm getting solid 34dBm (2.5W) into the cavity without any issues. I can also run the experiment using a single application now when before I had to use two. 