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borjam

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Everything posted by borjam

  1. A microwave oven uses an enormous amount of power of course. The thermal effects due to using a mobile phone are negligible compared to walking under the sun. Of course some of the more surreal "studies" are suggesting exotic explanations linked to oxidative stress, "artificially polarized radiation" and whatnot. Not so much. 3G and 4G are working on the frequency bands used formerly for television broadcasts. When I say "radio" I mean radio transmissions in general, including TV. And humans have been exposed to powerful radar transmissions on higher frequencies, such as 5 GHz (meteo radar) and 10 GHz (shipping radar) for many years. What may cause just certain frequencies to be dangerous and not others? And what about the powerful infrared radiation emitted by the now phased out common incandescent lamps? Depends on how far of the multi KW transmitter you are. Go to a roof in an urban area and check with a spectrum analyzer. The strongest signals (around -20 dBm on the roof of the University here) are the FM broadcasts. They interact with each other like two people speaking simultaneously. If the signals are strong you can even suffer intermodulations of course. However, will two improperly set up transmitters cause damage to the receiver? No They don't interact with each other, the problem is in the receiver if the spectra of the signals somehow overlap or one of them causes non linear effects (distortion, intermodulation) on the receiver. The classification as "possible" is not even a hint. Lots of substances and agents are classified as "possible". It was a statistical artifact. I don't have the explanation here (I can dig it) but it really didn't prove anything. Also, there was no indication of dose response. And we are talking about a study done with mice especially susceptible to cancer. Well, statistically in a population of millions of people using mobile phones and wireless devices daily not all of the cases would develop at the same pace. We would have seen it already. There are lots of poorly made studies pretending to show something. The well done studies show nothing. Yet there are some people succeeding in keeping some "controversy" around the subject, the same kind of "controversy" around evolution or vaccines. It is impossible to prove that something is harmless. However, if you fail to prove any harm you can have a pretty good assurance that it's not harmful. My apologies, this is a peaceful forum and I am not intending to begin a war on the subject. But, really, unless substantial proof is shown (so far there is none) I won't stop using wireless devices.
  2. Digital systems such as Deity Connect rely on the feedback sent from the receiver to the transmitter in order to work. The receiver will acknowledge received packets and maybe send information on received signal quality so that the transmitter can decide to retransmit, switch frequency and/or even data coding. So, in an Orwellian way, war is peace and receivers are transmitters Larry gave a really good suggestion above, increasing the packet transmission rate so that interference moves to ultrasound frequencies. It depends a lot. As a general rule there are two possible effects here: Either the radio equipment is transmitting interference outside the intended frequency band (unlikely, the certification process should detect that) or the recorder/preamplifier/microphone is detecting radio frequency. The latter could be solved by proper filtering and shielding but it's pretty expensive to develop. The RF Explorer manufacturer sells a set of near field antennas for electromagnetic compatibility testing but they are intended for a different application, such as detecting harmful emissions from devices not supposed to transmit such as monitors, power supplies, etc. Now I got curious, I will try to torture my MixPre 3. I am a radio amateur and I can try recording while I transmit on HF or V/UHF frequencies and expose it to heavy WiFi traffic. But if I am not wrong according to the internal photos its inputs seem to be transformer coupled, and transformers are a natural low pass filter.
  3. First: Physics. Remember that we are made of atoms. We do know pretty well what happens when electromagnetic radiation interacts with matter. Especially, we do know pretty well that in order to obtain a non-thermal you need a pretty high energy photon. EMR with such high energy photons is known as "ionizing radiation" and its frequencies are above those of visible light, slightly above ultraviolet-A. If UHF "photons" were dangerous, visible light photons would be lethal. Second, electomagnetic radiation in the UHF frequencies used by mobile phones is not new. Some of the bands have been used by analog TV broadcasts since the 50's or so, with transmission powers in the order of several KW. I remember an image in Madrid, around Torrespaña (a large telecommunications tower surrounded by residential areas). Houses around it had the TV antennas attached to windows and balconies instead of the typical pole on the roof. Is there a know cancer cluster there? Not at all. That adds some historical data to the "we would already know" argument. The radio spectrum is quite densely populated. It's not only mobile phones, but radio and TV broadcasts, utility radio, radar, microwave links, etc. For example, have you ever visited a harbor or boarded a small ship with radar? Civil marine radars usually work on the 10 GHz band (5x to 10x frequency of the mobile phones), transmit pulses (some phobiacs now claim that pulsed transmissions are more harmful) and with powers up to 45 KW. I guess fishermen have a higher risk of skin cancers, but, is it the sun or the radar? So what's different between the old analog system around 450 MHz, GSM, 3G, 4G and 5G? Some frequency bands have been reused. And the more modern the technology, the more efficient its transmissions, which means that they require less energy to transmit the same amount of information. I guess some people became paranoid with GSM mobile phones because the transmission is so incredibly dirty interference can be heard on a nearby passive loudspeaker. There are no increases in cancer cases that you could link to mobile phone usage and it's been more than twenty years now. The cancer cases linked to people working around radars are not caused by the radar microwaves (non ionizing) but by X-ray leaks affecting operators (X-ray is well above ultraviolet, so it's certainly ionizing radiation and very harmful). Mainteinance staff can be at risk of inhaling harmful substances when repairing power electronics because well known dangerous substances are used. Again, nothing related to radio transmissions. I don't think we have reasons to think that it's dangerous. Of course tobacco companies denied the harm while lung cancer cases were raising dramatically. The same thing is sort of happening now with the controversy around diesel. Better than gasoline in the long term (it emits less CO2) but really bad in the short term (it emits very harmful pollutants linked to lots of cancer cases in urban areas). There is no physical effect that might explain any kind of harm. Frequency or application selective? Forget it. Cancer cases? Nothing. Studies? A large long term study carried out recently with mice gave a quite convincing result: nothing. Actually, as a statistical artifact EMR was beneficial! Yes, there is a well known Spanish biologist claiming that EMR is decimating bird populations. The guy even dared publishing a "paper" in which he showed that he was unable to distinguish mobile phone transmissions from radio broadcasts in a spectrum analyzer and he quoted the "measured radiation levels" in plain dB. Not dBµ, dBm or whatever. Even the surroundings of Chernobyl, where there is indeed a lot of extremely harmful nuclear radiation, have become a wild life haven. Yes, there are no cell towers there. Might as well be a worthy experiment to plant several active cell phone mast simulators there and see what happens. I really don't think we have any reasons to worry at all. I am deeply worried about the impact of social networks and instant communication on democracy but that's an entirely different matter. So far there's no proof, not even indirect. Meanwhile we have really strong reasons to think that it's harmless. And as a research subject for a physicist it would be like a dream. Someone proving and describing such a harmful effect would be a good candidate to become a Nobel laureate on Physics or Chemistry. It would certainly demolish a lot of what we know about matter.
  4. Oh no, no antennaphobiacs here, please! If mobile phones were dangerous at all we would be seeing the effects years ago. Wondering about the insane "talent" embracing homeopathy, anti vaccine movements, 200$ a shot "detox" smoothies and all that crap, how do they react to radio mics?
  5. I wonder if part of the problem is that envelope of the transmitted bursts is too sharp. I remember with horror the terrible GSM phones, I always wondered how that utter crap could be approved.
  6. Ferrite beads on the audio cables should be more effective than a copper sheet I guess. After all the F4/F8 cabinet is metal, right? I am wondering about the internal antennas in the Deity receiver. Can they be disabled through firmware?
  7. I admit I use it on my iPad sometimes, and I keep it on the Apple users forum because some people asked for it, but it't a royal piece of crap. Last week I lost a long, thoughtful post on a bird watching forum because Tapatalk decided out of the blue to truncate my post to a couple of paragraphs. It wasn't any kind of configuration limit, it even broke a phrase in the middle. My stance on it (on the forum I administer) is: As long as the headaches it causes are markedly less than the bunch of users demanding it stays. The moment it becomes a chore itself it will be deleted summarily So, my recommendation as a forum admin: avoid it because it already caused some headache. (LarryF, you would love that forum thread, I am fighting some "antenophobiacs" who preach about an electromagnetic genocide of sorts. You know, radio transmissions causing a decline of insects, birds, etc)
  8. That's curious, is Invision updated? I run a Mac users forum with more user activity and it's working for me. Although, well, both Tapatalk and Invision sofware are rather kludgy.
  9. This insanity has other serious consequences as well. Macos X is a very robust operating system and you don't need to keep your audio computer in a sort glass box for fear of damaging something. I use the same machine for audio edition, software development and general Internet surfing. But Protools is a serious problem (I use Digital Performer). If you have to wait for Digidesign's blessing to install an operating system update you might be at risk. Some contain important security fixes. I usually advise Protools users to use Firefox as a web browser instead of Safari. You can update Firefox without affecting the operating system in any way.
  10. I wonder what's wrong with Avid's software development. Most Mac OS X version transitions, especially since 10.6, have been rather uneventful for software developers. I guess Protools might still have some Jurassic code in it. I kept using some Elemental Audio plugins until Apple removed Carbon in 10.13. The plugins were so old, the authorization generator only worked on PowerPC so I had to copy the license files carefully when moving to one machine from a new one, being unable to regenerate them.
  11. Although limited, you can use two cardioids for the S channel. Place them perpendicularly to the axis of the M microphone, one pointing to the left and another one to the right. S will be the sum of the left microphone and the right microphone with the polarity reversed. Try to place the diaphragms as close as possible to minimize phasing issues though. Sound Devices added polarity reversal to the MixPre 3, so you can do this trick with it.
  12. Rycote offers a really excellent selection of spare lyres with different degrees of stiffness. Last month I ordered some to modify a Rode Blimp. I'll need to make a couple of small spacer adapters but it's certainly easy. I ordered the spares from Audiosense (Belgium) but I imagine any Rycote dealer can supply them. This is the reference pages for the Lyres and other upgrade parts, http://mymic.rycote.com/products/lyre/ And, for example, Audiosense lists them on their web page. They had a 3 week lead time though, in my case they didn't stock the parts. Confusingly, they list them as "Shockmounts and Suspensions" rather than "Spares" or "Upgrades". Still, really useful and I found the prices more than reasonable. https://www.audiosense.be/en/store/microphone-accessories.html?brand=rycote&category=shockmounts-suspensions&limit=96
  13. Oh well, the signal integrity requirements are certainly different. Digital signals tolerate certain amounts of noise that would make a transmission channel unusable for quality analog transmission. But of course at the end of the day signals are signals and common transmission line problems can ruin your day. Exhibit one, a silly example. Unterminated RS485 serial bus (note the overshots). It worked but before terminating resistors were installed it tended to fail sometimes. I guess when someone went near the unshielded twisted pair cable with a mobile phone. The second image shows a better terminated bus. Now, modern networks at high speeds enter the realm of microwaves, where circuit design needs to take Maxwell's equations into account rather than simple Kirchoff's Laws Try to assemble a digital circuit on a simple breadboard. It will work at 1 MHz. Now try 100 MHz I understand that he means "no analog gain stages" or even "no active components in the analog signal path".
  14. Hehe, a recorder with a single tape reel letting the tape loose (or, better yet, shooting it away at a speed of 15 ips) would fit in this collection (An arrangement of eraser head right after the recording head wouldn't be so obvious for a casual observer!)
  15. I wonder wether the detuning effect caused by the body in the near field has been taking into account. That effect should be maybe a little less for higher frequencies. I remember when I mentioned the 60 GHz band, with a wavelength of 5 mm the body would be in the far field. I guess the detuning effect is worse than absorption? I remember two years ago I saw some flat magnetic antennas designed to sit on metal enclosures. It was a discreet antenna (so it could be used in vending machines without stupid users breaking them off for fun) and indeed they didn't tune properly if placed on a wooden table (according to my toy VNA). But they worked pretty well when attached to a metal surface. The same manufacturer has a model or two designed to be taped on glass as well.
  16. Thank you, my information source was indeed the FCC internal photos. When looking at the ADC specs I was indeed a bit surprised! So that explains it
  17. Hope I wasn't too blunt! I was just thinking about beginners getting confused with the terms. That would make sense, modern A/D converters implementing better digital filtering. This one is used in MixPre-3: https://www.akm.com/akm/en/file/datasheet/AK5558VN.pdf And it has some nice features such as four different types of digital filters. I was puzzled when I read that they used 32 bit converters, maybe that's the reason. Also I noticed that it can use a neat trick (summation) to increase S/N ratio. Cirrus Logic explain it very well here. I had never heard of this, you can learn new tricks everyday https://statics.cirrus.com/pubs/appNote/AN331REV1.pdf
  18. Hmm. I think you are confusing bit rate with resolution. Bit rate is the product of resolution (bits/sample) by sampling frequency (sample/second). But both factors are not interchangeable. Increasing resolution won't affect the Nyquist frequency which is determined *only* by the sampling rate. It's true that perfect analog filters do not exist, so the behavior of the filter is not so good at frequencies close to the Nyquist frequency. So yes, oversampling is a solution to that. You can use a simpler analog filter with the cutoff frequency much higher than the intended maximum frequency of your application, and add a digital filter (which is cheaper and more effective to implement) to "clean" the bandwidth portion between your intended maximum frequency and the actual Nyquist frequency of the oversampled converter. Trying to make it clearer. Let's imagine an A/D converter with an intended band pass of 20 KHz (good old audio) and a "visible" sampling frequency of 48 KHz. We can make it the straightforward way, adding an analog filter in front of the converter. Let's say the cutoff frequency is 24 KHz. But it will affect the phase of a signal being sampled depending on its frequency. The closer to the limit, the worse. And of course it won't cut frequencies right above the cutoff frequency very well. Now, let's do 2x oversampling. We sample at 96 KHz, so we can put the filter on, say, 48 KHz. So in the digital domain we have a sampled signal with a bandwidth of 48 KHz. We still need to clean up it before down converting to 48 KHz sampling or aliasing will happen. The analog filter is always necessary. Aliasing is an irreversible phenomenon. Once a signal outside of the Nyquist limit has been sampled it becomes indistinguishable of a signal below it. That's the reason why ultrasound can create aliasing. But with oversampling you can relax the analog filter specifications a lot and rely on a cheaper to implement and more flexible digital filter. Reality is a bit complicated and the actual problem with aliasing is to pretend to sample frequencies *both* above and below the Nyquist limit, but this phenomenon mostly has applications in other fields. You can search for information about "Nyquist Zones" but unless you are into software defined radio or other similar applications it won't have much interest for you The first Nyquist zone would be from 0 to Fs (Fs = sampling frequency), the second zone would be Fs to 2Fs, etc. So, you can sample signals between Fs and 2Fs as long as your anti aliasing filter is a (Fs, 2Fs) band pass filter.
  19. But bear in mind that the MD441 is maybe the most expensive dynamic microphone currently available and the RE-20 is in second or third place in the ranking. The RE20 has a clever design that minimizes proximity effect despite being directional. It’s more popular in USA as far as I know and it was designed for radio stations. i have only tried it on a double bass and the result was pretty good.
  20. borjam

    scorpio!

    It doesn't look like the Kashmir preamp at all. Remember that the Scorpio offers adjustable limiters while the MixPres have a fixed time constant and threshold level.
  21. At least in Spain the MD441 is the standard microphone at radio stations. I love it for live concerts, especially horns. It also saved my life with a violin once in a very difficult concert. A friend who had a voice over studio in Spain was a big fan of the CAD e300, which is not expensive. And speaking of "emulations", Austrian Audio, from the ashes of AKG, have announced a really curious beast: the OC 818. https://austrian.audio/produkt/oc818/ It's a dual diaphragm LDC which allows the user to record the output of both capsules, including a plugin to process them and adjust a custom polar pattern with programmable crossover points. The idea sounds interesting.
  22. Speaking of recommended mics, there is a Belgian seller on eBay offering AKG SE300B+CK93 at a very good price. I purchased a SE330B+CK93 combo and an additional CK93 and they are in perfect condition. Only complaint, the seller insisted on charging for the shipping of _each_ item.
  23. Now that I think of it, the main advantage of those 32 bits will be a better limiter implementation in software without degrading resolution.
  24. Yes and no As I intended to say, I can imagine an instrumentation microphone emulating the "personality" of another one intended for music. With limits of course (off axis response would be impossible!). But I am really sure my old SE2A microphones won't emulate a Schoeps! Don't get me wrong, *part* of a microphone characteristics come down to some eq, but there is a lot of reluctance against it and many multi microphone lockers could be almost equivalent to a lesser collection. In hindsight I think in the past I heard about audio plugins purportedly emulating different microphones.
  25. I think I heard of them some time ago. Interesting to somewhat copy the frequency response and distortion of popular microphone models. But what about the off-axis response which can be so important in an untreated room? Or, as they show the EV RE-20 as one of the emulated microphones, how to reproduce the lack of proximity effect? Will the plugin have a control to state the distance between speaker and microphone? I am really skeptical about this, I guess you can achieve similar results using some EQ in post. Last month I tried to explain a physicist friend what's the difference between the sound of different microphone models and why it's so important. I explained him that not only the on axis frequency response (which would be reasonably easy to replicate with EQ) matters, but also the off axis response and distortion. Of course it was trivial for him to understand frequency responses, noise floors and maximum SPL. But there are many sound characteristics that we are unable to represent just with a bunch of numbers. After all distortion is a non linear complex phenomenon and a mere percentage doesn't tell the whole story.
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