Author Topic: Spectrum Analyzer - Rigol DSA815  (Read 615563 times)

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Offline olsennTopic starter

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #25 on: April 11, 2012, 10:10:29 pm »
Another thing I have noticed is that if you manually override the sweep time to something lower than the recommended one, or in the case of (for example) a RBW of 100Hz in Full Span (1.5GHz) mode (where you are forced to use a sweep time lower than what would be recommended if the device could sweep longer than 1500s) a little blue "UNCAL" box shows up at the top of the screen to let you know that the device can't meet its specs at this setting. You can see this in Figure 1 in the document previosuly posted.

To prevent confusion, the DSA815 is not limited to RBW's of 100Hz, 1KHz, 10KHz, 100KHz, and 1MHz. Additionally, you can select a RBW of 300Hz, 3KHz, 30KHz, or 300KHz. This is known as the 1-3-10 sequence 
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #26 on: April 11, 2012, 10:37:49 pm »
olsenn,

Thanks much for the clarifications. So, do you LIKE your DSA815? Is it worth the money ($1,200-$1,500) ?
 

Offline olsennTopic starter

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #27 on: April 11, 2012, 10:57:26 pm »
Quote
Thanks much for the clarifications. So, do you LIKE your DSA815? Is it worth the money ($1,200-$1,500) ?

To be honest, I'm still getting used to it. I've never owned a SA before, and I still have much to figure out about this one. So far I do like the device and I think it is pretty safe to say that the DSA815-TG is the only real contender for a sub $2000 spectrum analyzer.

I still need to hack together some sort of active probe to get any real use of the tracking generator, and apart from Rigol charging extra fro the advanced measurment functionality (which I have not purchased) my only real complaint so far would be the lack of a probe power port on the device. Don't buy the cheaper unit without the tracking generator by the way; that would be stupid. The tracking generator must be purchased with the unit, but the other add-ons can be purchased later if you wish, and all you need to do to activate them is enter an alphanumeric code in the device... perhaps eventually someone will leak some codes out over the internet (unless they're tied to the serial number of the device). I've tested its programmability through VISA commands and that works like a charm.

One thing that frightens me, and this affects all spectrum analyzers out there, is the 50-ohm input. I have a 30db attenuator in the mail that I purchased on ebay, which will hopfully add sufficient input protection. Fortunately, the DSA815 is AC coupled, so you can have a DC offset of up to 50V without damaging the device. 20dbm, or little over 2Vrms AC can damage the device if no external attenuator is present; although in the datasheet Rigol does claim that a protection switch will be enabled if more than 25dbm goes through the input. When I connect my Rigol DG2041A function generator up to it (directly) I get unexpected amplitude readings, although I'm sure this is my fault for being an idiot, haha. Actually, it may be 1/sqrt(2) of what I was expecting???

Most importantly, it also functions as an AM/FM radio :)

 
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #28 on: April 11, 2012, 11:48:58 pm »
I like these guys for attenuators:

http://www.jfwindustries.com/catalog/Fixed_Attenuators-4-1.html

Another late comment from the Rigol Tech Support rep:


Quote
"I didn't mention that the Peak Hold feature of the analyzers will allow
you to do "N" sweeps capturing the peak value in each "bin".   That way
you can see all the hops or transmitters that come up over time."
« Last Edit: April 11, 2012, 11:53:05 pm by NukerDoggie »
 

Offline rf-loop

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #29 on: April 12, 2012, 05:22:26 am »
Well, here's the response from Rigol on the DSA815:

See attached pdf from Rigol.

Looks pretty decent to me - what do the rest of you think?

In attached pictures there can see many things.

Of course Rigol AD man can tell:
 
"Typical -135 dBm Displayed Average Noise Level (DANL)"

Really typical - owb

And after then careful people look more deep and example these Rigol pdf pictures and...

I remember some year around  ~1980 I buy US made some "Hi-Fi" amplifier... wow.. AD paper brochyre in shop tell it is 100W amplifier...
Well... yes it was... total power consumption from AC line was round 100W.

Dream image what AD give is sometimes far way from real world truth or sometimes people believe AD tell same what he think but maybe they are different things... just example amplifier... AD talk total power consumption but I think amplifier output power... and I believe AD talk just this. (without looking more deep what they really talk)

But, Rigol... not bad at all in this 1k$ price class.
« Last Edit: April 12, 2012, 05:24:49 am by rf-loop »
I drive a LEC (low el. consumption) BEV car. Smoke exhaust pipes - go to museum. In Finland quite all electric power is made using nuclear, wind, solar and water.

Wises must compel the mad barbarians to stop their crimes against humanity. Where have the wises gone?
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #30 on: April 13, 2012, 02:10:13 am »
My primary interest in the DSA815 is in using it for EMF / EMC. I manufacture prototype medical devices in the field of photo-biostimulation, employing arrays of 820nm infrared LEDs that are mounted in a custom-molded fiberglass casting that fits a particular patient's neck/shoulders. I'm in the medical trials phase presently. I'm treating patients with neurological disorders (like MS and PLS) by irradiating the cervical spine in order to dissolve scar tissue in the regions where the upper motor neurons and the lower motor neurons interact with each other. This takes time (many months) and requires that the patient wear the casting for 10 minutes, 3 or 4 times a day, while the little devils (240 infrared LEDs) happily irradiate their tissues. These are 100ma LEDs arranged in 16 strings of 15 LEDs each.

Since the casting is in very close (intimate) contact with the patient for up to 40 mins every day, and I'm using 24vdc and PWM intensity control, we've got lots of nice sharp square waves with RF ringing all around the patient's neck and near his/her head. So controlling EMF is a big issue. The FDA requires that you keep it under certain levels, for obvious reasons. So the DSA815 looks goos for my purposes, at first glance.

Of course, some of that nasty RF ringing is in the scope probes - but how much? An SA configured to monitor the EMF spectrum is very desirable (no, a necessity). I already have several EMF meters that I use to verify the levels are very low (thanks to countermeasures taken) but a visual and more respectable confirmation via a decent SA is what I'm after.

Any comments or suggestions would be much appreciated.
 

Offline dfnr2

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #31 on: April 13, 2012, 05:45:01 pm »
Since the casting is in very close (intimate) contact with the patient for up to 40 mins every day, and I'm using 24vdc and PWM intensity control, we've got lots of nice sharp square waves with RF ringing all around the patient's neck and near his/her head. So controlling EMF is a big issue. The FDA requires that you keep it under certain levels, for obvious reasons. So the DSA815 looks goos for my purposes, at first glance.

I believe that if the device meets the EN/IEC 60601-x standards, then any FDA standards will not be an obstacle.  Some devices, such as MRI coils, produce strong RF near fields, resulting in RF deposition and patient heating, and are subject to additional FDA regulations, but I doubt those would apply to your device.

for EMC precompliance testing, I have an HP 8591E with the quasi-peak detector, but I believe the quasi-peak detector really not necessary--I haven't used it yet.  If, as you indicated, you baked the EMC precautions into the device, then hopefully all the peaks will be within spec anyway, and if not, you want to bring them down as much as possible.  The quasi-peak detector will be useful for those borderline peaks you just can't reduce any farther--they may actually meet requirements if measured with the quasi-peak detector, since that's how the standard is defined.

Looking at the Rigol, it appears very attractive.  Certainly very portable, which is a plus.  If you get one, I'd be very interested to hear how it works out.

Dave
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #32 on: April 14, 2012, 02:55:22 am »
I would dearly LOVE to see a review and teardown of the Rigol DSA815-TG!!!

Please!!!
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #33 on: April 14, 2012, 04:31:34 pm »
Response from David L. Jones:


Quote
Test gear doesn't just magically arrive for review, I have to somehow acquire it first :-> But as it so happens I am talking to Rigol US about reviewing gear, and that one was on the list. So maybe it will happen.

David L. Jones
www.eevblog.com
The Electronics Engineering Video Blog
 

Offline olsennTopic starter

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #34 on: April 14, 2012, 09:48:56 pm »
Quote
Looking at the Rigol, it appears very attractive.  Certainly very portable, which is a plus.  If you get one, I'd be very interested to hear how it works out.

Here is a photo to show how the size of the device compares against some of my other tools.


free picture hosting
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #35 on: April 15, 2012, 12:07:49 am »
That 8" screen on the DSA815 is really nice!

Well, since EMC is going to be my primary application for the DSA815, I'm looking into acquiring a suitable wideband antenna - perhaps a dipole or maybe a log periodic antenna (array of dipoles). They can be very expensive, a lot more than the SA itself - I want one of my own, I don't want to rent.

I'm wondering if I can build one and get it calibrated/certified, or at least compare it to one that is and document the variances?

http://glendash.com/Dash_of_EMC/Log_Periodic/Log_Periodic.htm

Hate to try to re-invent the wheel, so to speak, but funds are limited at this point. I'll be able to purchase the SA but I'm not in a position to spend another $800 to $1,500 or more on an antenna. And the Rigol EMC measurement kit, though fairly reasonably priced, may not be suitable for my needs. They don't tell you much about it. I'll have to investigate further to see exactly what it consists of.

I'll have to admit that, even though I'm probably not being real practical, the idea of designing and constructing my own EMC antenna is intriguing and revs up my motivation quite a bit. ( I LOVE anything RF!)

If anyone here has links or any suggestions at all, I'd like to hear them.
« Last Edit: April 15, 2012, 04:54:42 am by NukerDoggie »
 

Offline olsennTopic starter

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #36 on: April 16, 2012, 01:24:51 pm »
Quote
I manufacture prototype medical devices in the field of photo-biostimulation, employing arrays of 820nm infrared LEDs that are mounted in a custom-molded fiberglass casting that fits a particular patient's neck/shoulders. I'm in the medical trials phase presently. I'm treating patients with neurological disorders (like MS and PLS) by irradiating the cervical spine in order to dissolve scar tissue in the regions where the upper motor neurons and the lower motor neurons interact with each other. This takes time (many months) and requires that the patient wear the casting for 10 minutes, 3 or 4 times a day, while the little devils (240 infrared LEDs) happily irradiate their tissues. These are 100ma LEDs arranged in 16 strings of 15 LEDs each.


NukerDoggie, it sounds to me like you want to use this thing for advanced medical research? I would imagine someone of your expertise would have to be able to afford better equipment than a cheap Rigol SA? Furthermore aren't there requirements that your test equipment be certefied to NIST standards and capable of verifying FDA or other medical standards?
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #37 on: April 16, 2012, 02:38:06 pm »
Quote
I would imagine someone of your expertise would have to be able to afford better equipment than a cheap Rigol SA?

Yep - but if you've ever been thru the FDA approval process then you know how expensive it is! While you're in trials, you are allowed a somewhat relaxed set of regulations. But once you try to get to production, you will have had to meet all the most strenuous regulations and specs. For that phase I'll have to use an EMC lab.

There's never ANY guarantee you'll ever get out of the trial phase, either. I'm not made of money, dude! I've already spent more than $250K getting to this point. It's been a long hard slog aready. And there's not much money left in the till by now.

But there are rewards - the technology does work. We can break up sclerosis (scarring) of the upper and lower motor neurons, though it takes many months to accomplish a measure of such progress.
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #38 on: April 16, 2012, 04:58:44 pm »
Another point - all indications are, at this preliminary point anyway - that the Rigol DSA815 is inexpensive, but not necessarily "cheap", meaning that they certainly appear to have done a pretty decent job producing a worthwhile instrument. I hope it turns out to be true, anyway. I'm encouraged at this point.

For those interested in EMC, here's some pretty nice EMC probles I located:

http://www.beehive-electronics.com/probes.html

There are other mfgs of such probes too, and you can spend more than the Beehive ones cost.

The nice thing about this approach to EMC is that probes such as these are designed to EMI-test your device without the need for a Faraday cage. The probes are quite sensitive to very near-field EMF (especially when used with a preamp), but not so much to the rest of the RF garbage floating around your lab. This allows you to better pinpoint what's actually coming out of your DUT. These look like they would be a nice match to the new Rigol DSA815-TG.
 

Offline jahonen

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #39 on: April 16, 2012, 05:14:32 pm »
In my experience, near field probing is quite difficult, at least to tell if the device will pass EMC limits or not. It takes quite a while to get a gut feeling what is normal and what is not.

This is because it is not usually the PCB what radiates. PCB directly radiates only if the layout is extremely poor. Furthermore, most PCB's have reactive nearfield which does not cause any EMC trouble but just shows up on near field probe making you think that this field is the source of a problem.

The dominant source (and much more difficult to get rid of) of the radiation is usually wires and cables attached to the device, so called common mode radiation. Much better indicator is to put each wire through those loop probes and then scan along the wire length to determine if the levels rise.

Regards,
Janne
 

Online nctnico

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #40 on: April 16, 2012, 05:44:06 pm »
For serious EMC work you'll need a shielded chamber. Its better to locate a company nearby where they have such a chamber + equipment for rent. In one afternoon you know which frequencies are causing problems. With that knowledge you can use probes to find where the problems are and fix them.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #41 on: April 16, 2012, 07:36:00 pm »
Great suggestions, jahonen. Very much appreciated!

nctnico - yes, for final certification I'm way less equipped and sophisticated than is required. I'll have to use a lab. But your approach sounds very practical indeed for pre-cert work, which is where I'm at now.

You guys are really helpful - thanks much!
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #42 on: April 17, 2012, 03:44:58 am »
Very crude indications of the level of EMF radiated from my device:

What electronics hobbyist doesn't like to occasionally disturb civilian radio reception??? When I started out, we used vacuum tubes, the ones with plate caps. Get an old TV power supply transformer (about 750VAC), recify it with some big flippin' selenium rectifiers (you know, those ones with the big fins) and filter it with some oil-filled caps, and then use it to power a raunchy Hartley oscillator operating in the AM band. Makeshift antenna made out of left-over wire, and we were able to drive the neighbors daffy when they tried to listen to their AM radios. We made some vacuum tube plates glow red-hot too!

Anyway - that was in the 1960s. As a matter of fact, an ordinary AM/FM radio isn't a bad detector for lower-freq EMF. Real crude - but at least you can get a general idea of how badly your DUT is radiating RF in the lower frequencies.

Out of curiosity I hooked up a non-shielded power pigtail (48 inches long) to my prototype medical device (the one with the LEDs pulsing away at 24vdc and 752 hz. Then I turned it on and brought an AM radio closer and closer - about 18 inches away I began to very faintly hear the 752hz whine, and at 1 inch away the whine was pretty loud. You could see (hear, actually) the inverse logarithmic relationship between power and the distance from an RF source. On FM - nothing - no interference at all.

Anyway - the device seems fairly quiet, by this crude test. I've got a great antenna - the unshielded power pigtail. I'm only 'transmitting' 18 inches. I could interpret this rudimentary test to mean I've got only a small EMF problem. Granted, I'm missing a whole lotta frequencies in my test. And this can NEVER take the place of a truly scientific approach. But, it is encouraging.

Or is it? Comments?
« Last Edit: April 17, 2012, 04:58:20 am by NukerDoggie »
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #43 on: April 20, 2012, 04:13:23 pm »
Well, I'm just 1 week away from ordering my new Rigol DSA815-TG. I got final approval from my boss (er, I mean, my wife). Of course, I DO wear the pants in the family ('cause she lets me). I plan to order a set of near-field EMC probes (Beehive-Electronics) and also a set of in-line fixed attenuators (JFW Industries) to go along with the instrument.

Pretty excited! I've lusted after a decent SA for several years, but could never justify the expense. Now I can! Thanks Rigol, and thanks Tequipment.net (I'm buying from them next week).
 

Offline olsennTopic starter

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #44 on: April 20, 2012, 04:41:05 pm »
Quote

Well, I'm just 1 week away from ordering my new Rigol DSA815-TG. I got final approval from my boss (er, I mean, my wife). Of course, I DO wear the pants in the family ('cause she lets me). I plan to order a set of near-field EMC probes (Beehive-Electronics) and also a set of in-line fixed attenuators (JFW Industries) to go along with the instrument.

Pretty excited! I've lusted after a decent SA for several years, but could never justify the expense. Now I can! Thanks Rigol, and thanks Tequipment.net (I'm buying from them next week).

You won't be dissapointed! I have been playing around with mine a fair bit and I am starting to get the hang of what all it can do. It is a very nice tool indeed. Please let me know what you think of those EMC (beehive) probes once you get them.

The real question is, does she let you NOT wear pants!
 

Offline wkb

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #45 on: April 20, 2012, 05:35:01 pm »
Quote

The real question is, does she let you NOT wear pants!

A kilt instead I presume?
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #46 on: April 20, 2012, 06:07:15 pm »
olsenn asks:

Quote
The real question is, does she let you NOT wear pants!

No! She doesn't like turkey legs! (yech!!!)

But I let her not wear anything she doesn't want. Wait a minute - double-negative there? Oh well.

I'm glad you're feeling better and better about your DSA815-TG. I really think Rigol's got a winner there, on specs and on price.
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #47 on: April 26, 2012, 01:57:05 pm »
Well, I've gone on the Rigol-USA waiting list, hoping to nab a DSA815-TG in about two weeks when they expect a shipment to arrive from the factory. Right now everyone is sold out of the instrument!

I placed my order today with Tequipment.net - lead-time is only 5-7 business days + shipping - so within a couple 'o' weeks I should be in EMC heaven!
« Last Edit: April 27, 2012, 09:45:25 pm by NukerDoggie »
 

Offline NukerDoggie

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #48 on: May 03, 2012, 01:54:22 am »
To the Moderator: I understand if you decide to move this post to another thread that is more relevant to the subject. I just wanted to get this experiment with RF shielding on record.

In my pre-compliance EMC efforts regarding my prototype medical device I must accurately measure the EMI being radiated from the DUT. To do that I need a good spectrum analyzer, an ultra-wide-band listening antenna and an RF isolation cage so as to block out virtually all RF but that coming from the DUT.

This post has to do with the RF isolation chamber. I have been experimenting with such a chamber and here are my findings, for the benefit of anyone else with similar needs.

I have a portable battery-powered transmitter-receiver pair mfg by Linx Technologies that operates at about 430 Mhz. These are being used as test assets to demonstrate when and if I have achieved a desired measure of RF isolation. I place the receiver in each of my experimental chambers and try to ping it with the transmitter from only a few feet away. If I can, then I have not achieved the level of RF isolation I am seeking. The receiver is extremely sensitive - able to receive signals at levels down to -118Dbm - which equates to little more than 1 picowatt - a very tiny signal level!

I have successfully tested this transmitter-receiver pair at a distance in excess of 2500 feet of separation from each other, with the standard whip antennas, just to illustrate how very sensitive the receiver really is. If I can get this receiver to 'go dead' within an RF isolation chamber then I have really accomplished something.

I have succeeded in doing just that. Here are the details:

I used 10 mil aluminum foil to construct a foil box with a lip all around where the lid clamps on, and a lid itself. The box itself has no holes or voids of any kind, except of course the open top where the lid fits onto it. The lid is clamped onto the box lip all around using large binder clips like you get at Staples office supplies. The box is a cube of about 18 inches square, but the shape doesn't matter. I use 10 to 12 binder clips to secure the lid in place all around, after placing the receiver inside the box. The homemade Faraday cage is not grounded. It need not be in order to snuff out RF radiation.

This cage demonstrates virtually 100% RF isolation at the 430 Mhz frequency. The transmitter is unable to reach the receiver at all. However, if I remove only a couple of binder clips from the lid and wiggle the lid edge just a little, then the signal gets thru. And I mean only a very, very slight gap being allowed between the box and lid.

But with all clamps in place, RF isolation is 'perfect'. No significant gaps exist for RF to leak into the cage, and the clamps also help ensure that box and lid are electrically One Conductor - very important for any Faraday cage.

 I was very pleased to discover that this very high level of RF isolation can be achieved so easily with materials that are cheap. Now, in practice, my isolation chamber won't be made of 10 mil foil, but rather of 0.090" or 0.125" aluminum plate, so as to make a chamber with good structural integrity. But you don't have to spend a lot of money - you just have to be very careful in the design and construction of your Faraday chamber.

Soon - a post on my EMC UWB antenna that is now under construction.
 

Offline amspire

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Re: Spectrum Analyzer - Rigol DSA815
« Reply #49 on: May 03, 2012, 02:04:24 am »
NukerDoggie, you may as well start a new thread on how your EMC work progresses.  I think it will be interesting and it deserves its own thread.

Richard.
 


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