Question regarding FCC wireless spectrum in the 700mhz range

R

Ripper70

Active member
Hey All,

I'm curious if the Audio Technica ATW R-100 wireless lavalier transmitter/receiver combo can still be legally used since it has an operating range in the 656-668 as well as the 728-740 range.

If so, how would using only this range affect the performance of the system?

I'm new to the whole audio for film making world so I'm not sure about the rules in this particular instance.

Thanks for any input.
 
Using any wireless device in the range from 698 to 806 MHz has been illegal since 12-June-2010. So using that system on the 728-740 MHz range is illegal now. http://www.fcc.gov/encyclopedia/wireless-microphones

That doesn't mean that people aren't still using them because the range is so small, and the new uses/users have not taken over the band (yet), and because the FCC isn't very effective at enforcement in many areas. If you were in West Undershirt, Montana, you might be able to get away with it. But in New York City, it would just be silly.

Using the ~650 MHz band vs. the ~730 MHz band will not make any significant difference in performance, assuming the gear is still operating properly. However, the interference landscape must be accounted for. NYC and other large US cities are frequently referred to as "RF Hell" because of the concentration of so many spectrum users. Some wireless mic users have taken to using spectrum analyzers just to find a channel that is free for the morning, etc.

You can look up spectrum allocation on a new web page from the FCC: http://reboot.fcc.gov/spectrumdashboard/searchSpectrum.seam
 
Any ATW-U101 system was available in one of the two bands, but no system could run both (at least, the ones I owned which were in the 656-668MHz range).

So, don't use the systems that run in the 700MHz range and you'll be fine, assuming you aren't in an RF-crowded area.
 
Alex H. said:
Any ATW-U101 system was available in one of the two bands, but no system could run both (at least, the ones I owned which were in the 656-668MHz range).

So, don't use the systems that run in the 700MHz range and you'll be fine, assuming you aren't in an RF-crowded area.
Click to expand...

Ah, so it's an either/or thing. I thought the two ranges in the 600's and 700's were the reason they were called them 'diversity' units (as in each transmitter had multiple spectra to operate in).

As for my RF area (not sure what that means) I'm guessing Brooklyn, NY would be considered crowded. Should I give up on the idea of a wireless solution until I win the Lottery to pay for a top-of-the-line set-up?
 
Ripper70 said:
Ah, so it's an either/or thing. I thought the two ranges in the 600's and 700's were the reason they were called them 'diversity' units (as in each transmitter had multiple spectra to operate in).
Click to expand...

Diversity refers to the unit having two antennae, each with a separate receiver. The receiver unit is constantly analyzing the reception between the two, drawing from the one with the strongest signal. It bounces back and forth, and this helps minimize dropouts.

Ripper70 said:
As for my RF area (not sure what that means) I'm guessing Brooklyn, NY would be considered crowded. Should I give up on the idea of a wireless solution until I win the Lottery to pay for a top-of-the-line set-up?
Click to expand...

Yes, Brooklyn is going to be crowded. Top-of-the line isn't going to solve that problem if it's a unit that operates in a crowded band. Check the "Audio 101" sticky at the top of the sound forum. You'll find a link in there to Sennheiser's frequency finder, and you can check your area for the least-populated frequencies.
 
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Results within a 5 mile radius of my zip code (11201) were as follows. Why would all these 700Mhz frequencies be listed as 'vacant'? It does specify that the range in the darker green shaded area have been reallocated and 'may' become illegal.

Not sure what to make of this data.

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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: prx_col"]
[/TD]
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[TD="class: colPadding, align: left"]29[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: left"]51[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
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[TD="class: colPadding, align: left"]52[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD]
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[TD="class: colPadding, align: left"]57[/TD]
[TD="class: colPadding, align: center"]728-734[/TD]
[TD="class: colPadding, align: center"]Vacant[/TD]
[TD]
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[/TD]
[TD="class: colPadding, align: left"]Vacant[/TD]
[TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
[/TD]
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[TD="class: colPadding, align: left"]58[/TD]
[TD="class: colPadding, align: center"]734-740[/TD]
[TD="class: colPadding, align: center"]Vacant[/TD]
[TD]
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[TD]
[/TD]
[TD="class: colPadding, align: left"]Vacant[/TD]
[TD]
[/TD]
[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
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[TD="class: colPadding, align: left"]59[/TD]
[TD="class: colPadding, align: center"]740-746[/TD]
[TD="class: colPadding, align: center"]Vacant[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD="class: colPadding, align: left"]Vacant[/TD]
[TD]
[/TD]
[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
[/TD]
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[TD="class: colPadding, align: left"]60[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
[TD]
[/TD]
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[/TD]
[TD="class: colPadding, align: left"]Vacant[/TD]
[TD]
[/TD]
[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
[/TD]
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[TD="class: colPadding, align: left"]62[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
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[TD="class: colPadding, align: left"]63[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
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[TD="class: colPadding, align: left"]64[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
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[TD="class: colPadding, align: left"]65[/TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
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[TD]
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[TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
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[TD="class: colPadding, align: left"]67[/TD]
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[TD]
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[TD]
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[TD="class: colPadding, align: left"]Vacant[/TD]
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[TD="class: colPadding, align: center"]Vacant[/TD]
[TD="class: prx_col"]
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[TD="class: colPadding, align: left"]68[/TD]
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5 miles won't tell you enough. That may be fine for other wireless mic users, but you have to factor in TV and other transmissions that can occupy the same space.

While New York is the aforementioned "RF Hell," these wireless units are frequency-agile, meaning that you can filed tune them to one of a selection of frequencies in its given range. That ups the chances of finding one that works, as opposed to one of the cheap systems that offers only 2 or 10 pre-programmed frequencies (or even older systems that have only 1).

In a 70-mile radius, it looks like there are five major broadcasters that occupy the 656-668MHz range on licensed frequencies, so you might be able to operate in that range.

700MHz is listed as "vacant" because the FCC has reallocated them but the spectrum isn't being populated just yet. It's already illegal to use wireless mics in that range.
 
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Well, it turns out that the U100 transmitters in question are not the "x" series and, therefore, operate in the 700 Mhz range.

Just out of curiosity, what are the consequences of using this spectrum considering they're listed as "may become illegal" in the Sennheiser frequency finder chart?
 
Ripper70 said:
Well, it turns out that the U100 transmitters in question are not the "x" series and, therefore, operate in the 700 Mhz range.

Just out of curiosity, what are the consequences of using this spectrum considering they're listed as "may become illegal" in the Sennheiser frequency finder chart?
Click to expand...

The most practical issue with using spectrum that is allocated as 'illegal'... is that interference will(may...) occur that will impact your production. To be sure if someone somewhere notices your 'little' signal, and calls the FCC...an the FCC sends out the black Marias... there could be more impact in terms of some sort of 'criminal' activity... 'pirate radios' often last for a few days, sometimes more, even when broadcasting in standard AM/FM bands...

in the case of the 700 MHz and between 700-750, various major carriers are, or are planning, to use that portion for the LTE (great white hope of high throughput wireless service...) services. (There's also some Public Safety blocks in there as well...)...

While I've not looked at the New York City spectrum in these bands, these bands had 'crud' in them in Washington DC as of about 2009 or so... (Haven't been back to check of late...).

Furthermore, just because a frequency is licensed, does not mean there's a continual transmission... take a spectrum shot at 9 AM... it may be quite different at 12 PM...

For so called 'white space' devices, that is those devices which use various 'bands' at limited power, but can change frequency to some 'unused portion', they must look to a database of the FCC licensees (provided by private industry at popular prices...), check the spectrum as it is 'right now'... well at least on the order of 24 hours... and then one can transmit depending the results of the database look up. The FCC seems to have the option of 'sensing without database lookup' open until they see a device that can accurately 'sense' and not use the database look up method.

This allows fixed or 'intermittently, region confined mobile' use.
 
Black Marias! I certainly hope the NYPD wouldn't allocate such significant resources for little ol' me!

That being said, would it make a difference based on the location where they were used? For instance, I have a location in Manhattan that's a basement bar. Another that's a rooftop terrace in Brooklyn.

Do these locations present the same challenges in terms of broadcast/reception or would the rooftop be subject to more interference and "eavesdropping" than the subterranean location?
 
Ripper70 said:
Black Marias! I certainly hope the NYPD wouldn't allocate such significant resources for little ol' me!

That being said, would it make a difference based on the location where they were used? For instance, I have a location in Manhattan that's a basement bar. Another that's a rooftop terrace in Brooklyn.

Do these locations present the same challenges in terms of broadcast/reception or would the rooftop be subject to more interference and "eavesdropping" than the subterranean location?
Click to expand...

The UHF band of which 700-800 is part, has more 'penetrating' capability, than 2.5 and 5 GHz (WIFI) bands... which of course is why the UHF band was used for TV... distance and the ability to get reception inside the house...

That said... I'd say a basement, especially if it is a 'sub-sub-basement'... would have little or no reception... but the roof top... could see for miles and miles and miles...

For example, when I scanned the area here in 'north' San Diego County, I could 'see' stations up 20 -50 miles in the 'flat low areas'. But when I'd go to a hill top, perhaps 500 feet above the 'flat'.. see for 100 and occasionally 120 miles. When looking at some HDTV channels I was able to pull in some LA stations with a usable signal, some 90 miles away. Then again... on some days could even get transmitters 40 miles away... such are the vagaries of RF...

There are FCC 'contours' which define the official 'range' of a licensed transmitter. But the amount of 'interference' to you, with your requipment may or may not be impacted. On the other hand, if you are in a fringe area of a licensed transmitter, your 'mic' may impact some other receiver in the area, and that would indicate you are operating an unlicensed transmitter.

As a note... if you are high up and operating your transmitter, it's reach is increased by not having as much interference, as well as a few other attributes about how radio waves interact with 'ground' or 'water' that may be along the path to the receiver.

A low milliwatt transmitter can be seen 'straight up' in outerspace... (for those paranoid about spy satellites...)
 
Ripper70 said:
Well, it turns out that the U100 transmitters in question are not the "x" series and, therefore, operate in the 700 Mhz range.
Just out of curiosity, what are the consequences of using this spectrum considering they're listed as "may become illegal" in the Sennheiser frequency finder chart?
Click to expand...

The Sennheiser chart should say "HAS become illegal". There is no ambiguity of status or timing. It is a done deal.

IMHO, trying to get away with that in a major city is pretty terrible idea. I wouldn't touch it with a 10ft pole.
 
Richard Crowley said:
The Sennheiser chart should say "HAS become illegal". There is no ambiguity of status or timing. It is a done deal.

IMHO, trying to get away with that in a major city is pretty terrible idea. I wouldn't touch it with a 10ft pole.
Click to expand...

Understood. For the record, the Sennheiser chart says, "Unoccupied channel - channels 52-69 have been reallocated and may become illegal."

Perhaps I can find a location in West Undershirt, Montana. Always wanted to do a Western.
 
How does one distinguish between the x-system and the non-x system?I have a pair and am not sure if it is the x series or not.

On the receiver it says:
Model ATW-R100
FCC ID: JFZR100
Canada: 1752231187:

On the transmitter it says:
FCC ID: JFZT101
Canada: 1752231187 Model: ATW-T101 Also,I have lost the pouch with a clip on that the receiver is supposed to be put in and attached to your belt.Where can I buy it and for how much?Thanks




 
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I think all wireless gear (for the US) must have the operating frequency stated someplace on unit. I used to have a U100 system but don't recall if the frequency block was stated or where it was located. Possibly inside the battery compartment(s). If the model # doesn't have the "X", it's probably in the 700MHz range. Otherwise contact ATUS.
 
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