Our wireless future is in question

[Captain Pierce]

Well, part of the problem with the 6Ghz Spectrapulse is that the FCC will only license them to broadcast 75 feet, indoors ONLY, when the technology is capable of something like 2.5 miles outside. At least according to AT... Of course, part of the problem here is that these outfits are still competing with each other even as they're working together to fight the WID's. Sennheiser, for one, is really dismissive of the Sabine 2.4GHz technology, but (as much as I like Sennheiser and my Sennheiser rep, who's come through for me as a dealer several times) I have a different experience with the Sabines... (BTW, while we're talking about higher-frequency systems not having the range, those Sabines have better RF performance for me than my Shure UC systems, which are about the only wireless system I've ever seen have dropouts on a regular basis.)

I had a 2.4GHz cell phone that killed my Netgear Wireless-G router every time it came in the same room (although, oddly enough, it was OK as long as it wasn't in the same room); but, like I said, the Sabine 2.4GHz wireless can co-exist with Wi-Fi in my real-world experience. Now, the question is, if (for example) Sennheiser and Shure were both to start shipping 2.4GHz, how crowded would that band get? Or, for that matter--as I brought up to the AT guy yesterday--assuming the FCC does let them crank up the power on the 6Ghz systems, how are those going to interfere with each other?

 

[puredrifting]

Hi Captain:

According to my conversations with Lectrosonics and a few other engineers, just one problem. The higher the operating frequency, the shorter the range and the more susceptible to intererference a sound wave is. The 2.4gHz band is already very crowded with cordless phones and Apple Airports and other wireless routing.

Based upon what I know, 2.4gHz is not the practical solution to our woes. 6gHz, as some of the manufacturers are testing, is definitely not good for anything other than close proximity conference rooms. Fine for AV installs but no good for us as sound mixers in the field, the range is really short and the signal strength is not robust at the higher frequencies.

This issue really is a conundrum.

Dan

 

[John Willett]

All true Dan,

but you have forgotten to mention something - these very high frequencies (GHz ranges) are actually microwave frequencies - I don't think people would like to have a microwave transmitter strapped to their body in close proximity to their genitals.

The solution is to find frequencies lower down.

But do Government listen ...........................

 

[puredrifting]

All true Dan,

but you have forgotten to mention something - these very high frequencies (GHz ranges) are actually microwave frequencies - I don't think people would like to have a microwave transmitter strapped to their body in close proximity to their genitals.(

Thanks for the heads-up on that, I, along with probably most users, did not know that.

Dan

 

[moonlitnite]

All true Dan,

but you have forgotten to mention something - these very high frequencies (GHz ranges) are actually microwave frequencies - I don't think people would like to have a microwave transmitter strapped to their body in close proximity to their genitals.

The solution is to find frequencies lower down.

But do Government listen ...........................

Hi John,

Too late! Everyone already keeps their AT&T GSM phones (iPhone, etc) in their pants pocket - it regularly transmits a 2 GHz keep-alive handshake to the cell site, keeping our family jewels nice and toasty...

Michael

 

[Thebes]

Ok, I am a total noob when it comes to wireless mics. I had planned to get a low end 2-channel system with lavs.

Am I to understand that there is no such system now which will be immune from likely interference over then next couple of years? Or does this only effect some current systems?

 

[Steve House]

Ok, I am a total noob when it comes to wireless mics. I had planned to get a low end 2-channel system with lavs.

Am I to understand that there is no such system now which will be immune from likely interference over then next couple of years? Or does this only effect some current systems?

Unless you have a pressing need for a new system right now you might want to wait 6 months or so until the dust settles. One thing is certain, low end systems are more likely to have problems in the new environment than will the higher level systems.

 

[mumin]

guys ,I have two Lectros 401 block 28 Should I start getting rid of them?

 

[puredrifting]

guys ,I have two Lectros 401 block 28 Should I start getting rid of them?

No, but you should contact Lectrosonics and find out how much they will charge you to change the boards out for lower spectrum frequencies. It should be around $500.00 per set, a lot cheaper than losing your rear on selling them.

Lectros also are one of the most powerful systems on the market and I am convinced that their filtration and power of their amplifier will be helpful on rejecting and overriding interference better than almost any other brand. Lectros are a great tool.

Dan

 

[Captain Pierce]

Hi Captain:

According to my conversations with Lectrosonics and a few other engineers, just one problem. The higher the operating frequency, the shorter the range and the more susceptible to intererference a sound wave is. The 2.4gHz band is already very crowded with cordless phones and Apple Airports and other wireless routing.

Based upon what I know, 2.4gHz is not the practical solution to our woes. 6gHz, as some of the manufacturers are testing, is definitely not good for anything other than close proximity conference rooms. Fine for AV installs but no good for us as sound mixers in the field, the range is really short and the signal strength is not robust at the higher frequencies.

This issue really is a conundrum.

Dan

Dan,

As I said before, I realize we're well into "he said/she said" territory here, but again, Audio-Technica claims that the 6GHz SpectraPulse is capable of a 2.5-mile range--eventually. The key word there is "eventually," because they're not trying to tell us that the system is capable of that now--because (as you very accurately say) currently it's "not good for anything other than close proximity conference rooms." But the gist of what they said is that they believe that SpectraPulse is their future, and that eventually the FCC will license them to run those systems at greater ranges and outdoors.

Of course, that's their story, and obviously Lectrosonics is going to tell you something different because they want you to buy their gear. (Not that there's anything wrong with their gear; before the flood, I had a couple of very old CR185 systems that I would have used a lot more if they weren't both on 169.505... ) Now, unfortunately, my company doesn't sell near enough Lectro to get to talk to their guys regularly (more's the pity), but at this point, you just know that they have to working on something outside the traditional UHF band, just in case.

but you have forgotten to mention something - these very high frequencies (GHz ranges) are actually microwave frequencies - I don't think people would like to have a microwave transmitter strapped to their body in close proximity to their genitals.

Most of us have 2.4GHz Wi-Fi running, and I'm guessing a large portion of us have 5.8GHz cordless phones (particularly those of us with Wi-Fi running ), so I don't really see the danger here. (But I always clip the body pack to the back of my belt anyways, so I have a certain amount of built-in protection for the family jewels... )

 

[moonlitnite]

Dan,

As I said before, I realize we're well into "he said/she said" territory here, but again, Audio-Technica claims that the 6GHz SpectraPulse is capable of a 2.5-mile range--eventually. The key word there is "eventually," because they're not trying to tell us that the system is capable of that now--because (as you very accurately say) currently it's "not good for anything other than close proximity conference rooms." But the gist of what they said is that they believe that SpectraPulse is their future, and that eventually the FCC will license them to run those systems at greater ranges and outdoors.
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Hi Captain,

Err, I don't think you will get AT to put it in writing that they'll have small FCC-approved wireless 6GHz tranmitters with a 2-5 mile range! At those frequencies, it would take much more power than our existing 30 milli-watt tranmitters; remember, the higher the frequency the greater the attenuation when it's not line of sight. I'm sure you've noticed microwave towers with parabolic antennas are up high on a hill or on towers to ensure an unimpeded path. And usually when dealing with very weak signals like a cellular signal, the receiver site has expensive low-noise receivers using exotic technologies like spread spectrum modulation. Seemingly not the kind of thing a manufacturer could affordably produce for our applications. But the thought of having talent hold a microwave dish while doing their lines does make me smile...

If someone has better info, please give us some details.

Happy Trails, Michael

 

[John Willett]

6GHz *is* microwaves - I would not want a radio transmitter at those frequencies on my body. rogar-KnockedOut(D

 

[j1clark@ucsd.edu]

The beacon testing that was conducted to see if the "white space" wireless internet devices could recognize already used spectrum by wireless microphone users was an inconclusive failure.

Dan

I don't know where you obtained the 'inconclusive failure' determination... but currently, given that the available today FM mics have no 'spectrum sensing', you are more likely to experience mutual interference from another mic.

What is also interesting, is that in your post, there was reference to moving mics up to say, 2.4 GHz... if that is not now already over crowded, and would require some form of 'sensing' to avoid interference from not only 'evil' white space devices... but your neighbor's Microwave Oven... radar, everyone on the block's WIFI device, Bluetooth devices, and any other kitchensink RF device... I have no clue how that is seen as some sort of solution.

Adding some form of encoding on the pilot frequency of the mic, some form of spectrum sensing and some form of moving to new channels, seems like a benefit in any case.

Sure it may be 'nice' for some to have 200 MHz of 'wide open' spectrum, now that many broadcasters have discontinued over-the-air broadcasts in the 512-698 MHz region... but that obviously is a waste for other applications.

 

[Captain Pierce]

OK, I'm no radio engineer, but...

The microwave range includes ultra-high frequency (UHF) (0.3–3 GHz), super high frequency (SHF) (3–30 GHz), and extremely high frequency (EHF) (30–300 GHz) signals.

and

While the name may suggest a micrometer wavelength, it is better understood as indicating wavelengths very much smaller than those used in radio broadcasting.

The way I read this is that "microwave" has less to do with frequency than with wavelength.

I'll also offer into evidence A-T's white paper on the Spectrapulse Ultra-Wide-Band (UWB) technology: http://www.audio-technica.com/cms/r...5cbf16ed2b64/spectrapulse_uwb_white_paper.pdf One of the more interesting quotes from this is:

Traditional FM microphone systems transmit about
50 milliwatts of average power. The SpectraPulse system transmits 40 nanowatts average power. This is approximately one million times lower than an FM system.

Finally, (and also according to Wikipedia), the 3.1 - 10.6 GHz band is also being developed for Wireless USB and possibly Bluetooth 3.0.

I'm really not trying to turn this into some sort of commercial for Audio-Technica or this technology, because currently it's not suited for most applications and anything else is purely speculation at this point. But the technology is here, it's working (in those limited applications), and having seen it in person, I can guarantee that there are no microwave dishes. (Although, during the demo, a number of Hot Pockets that were in the refrigerator in the kitchen next to our conference room were mysteriously cooked... rogar-Love(DBG): )

 

[moonlitnite]

Hi Captain Pierce,

Thanks for pointing out the interesting article. It will be interesting to discover AT's specs for typical working distances for their TDMA-based design. Let's hope they've taken these factors into consideration for their spread-spectrum ultra-low power gizmos:

Microwave System Equations

Again, I'm a "doubting Thomas" for this technology to effectively cover long distances.

Thanks again, Michael

 

[j1clark@ucsd.edu]

Finally, (and also according to Wikipedia), the 3.1 - 10.6 GHz band is also being developed for Wireless USB and possibly Bluetooth 3.0.

And also recall that Bluetooth distances are about a few hundred feet in 'good' conditions... or so... I would imagine this would be the same for the higer frequencies as well...

It may be useful for some apps, but for those apps that I could imagine for entertainment, such a distance may be limiting.

Then there's line of sight...

You can sort of approximate this with your WIFI or Bluetooth device, which operate in the 2.4 GHz band, and find out how far you can go... like maybe the parking lot next to the Starbucks that has WIFI hotspot...

Then there is the 'pringles' antenna to get 'miles' out of a 100 mW WIFI device...

(As note, one of my script ideas for someone who has been kidnapped by terrorists is for the victim to get access to a micro wave oven and point it straight up and send Morse Code SOS signals that are picked up by a spy satellite...)

 

[John Willett]

Also remember - the higher the frequency, the more signal is lost in body absorption and the more signal is lost down antenna cables..........................

The 50-Ohm RG58-CU cable used for radiomics has an loss of dB per 100m as below:-
20dB @ 145 MHz (VHF)
24dB @ 200 MHz (VHF)
47dB @ 500 MHz (UHF)
272dB @ 5 GHz (Microwave)

(source)

So your signal loss down the antenna cable will be about x5 the amount that you are now getting - as well as a much shorter range.

Things to be aware of.....

 

[Bucknfl]

http://www.lectrosonics.com/PressReleases/whitespace/whitespace.htm

"The Sky is not Falling" from Lectrosonics

 

[Bucknfl]

Block 27, 28, and 29 will no longer be legal as of June 1, 2009 and Lectrosonics are not building any wireless systems in these frequencies. Anyone know if the old wireless will work at all in 27, 28, and 29 after June 1st?

 

[Bucknfl]

A lot of used wireless systems in block 27, 28, and 29 are for sale on ebay. It looks like a lot of people are dumping them.