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Author Topic: WWB vs AT-3000 Scan Groups  (Read 380 times)

Mike Karseboom

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WWB vs AT-3000 Scan Groups
« on: June 07, 2021, 12:37:41 PM »

I am trying to use 4 units of generation 2 and 3 AT-3000 series D band in the unlicensed portion of the 600Mhz "duplex gap".  So I am trying to coordinate 4 frequencies between 657-663Mhz.  I am pretty rural (Mt. Shasta, CA) and there don't appear to be any TV signals in that range.  Also, no other wireless concerns in this range.


The AT-3000 units can actually go from 655.500 - 680.375 (so technically not legal?) but I am keeping them in the 657-663 range.




My question is comparing WWB 6 analysis/calculation coordination results with AT-3000 gen 3 manual published "scan groups".  The scan groups are supposed to be a list of frequencies that coordinate well without interference.  There are 9 different groups with different coordinated frequencies but you are supposed to just stay in one group and use those frequency choices.


When I use WWB and lock 4 frequencies that are in AT's published scan group 1 and supposed to be coordinated, WWB reports some as being incompatible - primarily due to adjacent units too close.  Example:  658.000 and 658.375 are good in the AT list but WWB says they are too close.  This is with standard (not Robust) level in WWB.


On the other hand, if I let WWB generate a coordination list, I get frequencies that don't fit in any of AT's published scan groups.  Instead, WWB's generated list will include frequencies that cross into multiple AT scan groups.  Those would possibly not be coordinated according to AT.


AT's published lists cause violations when plugged into WWB and WWB's calculated frequencies don't fit into AT's lists.  Which coordination would be the best to use?  The published AT-3000 scan group or WWB's calculated frequencies.
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--Mike
"If you're not confused, you don't know what is going on"

Live Sound for the Mt. Shasta area
http://www.shastalivesound.com

Russell Ault

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Re: WWB vs AT-3000 Scan Groups
« Reply #1 on: June 07, 2021, 03:58:23 PM »

I am trying to use 4 units of generation 2 and 3 AT-3000 series D band in the unlicensed portion of the 600Mhz "duplex gap".  So I am trying to coordinate 4 frequencies between 657-663Mhz.  I am pretty rural (Mt. Shasta, CA) and there don't appear to be any TV signals in that range.  Also, no other wireless concerns in this range.

The AT-3000 units can actually go from 655.500 - 680.375 (so technically not legal?) but I am keeping them in the 657-663 range.
{...}

There won't be any TV stations there any more. The duplex gap exists as "dead air" between the new cellular uplink and downlink frequencies, so wireless microphones are about the only thing you'll see there now. And yes, just to be clear, operating those units in the duplex gap (or anywhere else in the US, for that matter) is now not legal.

{...}
AT's published lists cause violations when plugged into WWB and WWB's calculated frequencies don't fit into AT's lists.  Which coordination would be the best to use?  The published AT-3000 scan group or WWB's calculated frequencies.

This isn't particularly uncommon (I think I've even seen this with Shure equipment, for that matter). The important thing to know is that manufacturer-published compatible frequency lists represent a very, very small subset of the nearly infinite number of total possible combinations. Put another way, there are probably well over one million different ways to program those four wireless microphones so that they'll all work well together within 6 MHz of available bandwidth, and A-T has published 9 of them for your convenience, but the chances of WWB spitting out only frequencies that are on one of those lists are less than winning the lottery.

Conversely, the criteria that WWB uses for calculating frequencies isn't necessarily the same as the criteria A-T used when it was generating those lists, and WWB tends to err on the side of caution (but not as much as WSM). One example is that, in my experience, many manufacturers don't include 3T3O IMD products in their published list calculations, while WWB often does. In practice what this means is that WWB set to "Standard" will typically produce a coordination that is technically safer than the manufacturer's lists, although this sometimes comes at the cost of spectral efficiency (but the ability to tweak criteria in WWB still makes it the superior choice in my mind).

-Russ

Edited to fix a really unfortunate typo!
« Last Edit: June 07, 2021, 11:46:00 PM by Russell Ault »
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Mike Karseboom

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Re: WWB vs AT-3000 Scan Groups
« Reply #2 on: June 07, 2021, 09:49:16 PM »

Russell - thank you for your informative reply.  Gotta love PSW - leave for a year and come back to well crafted replies from knowledgeable people!


I managed to find a set of frequencies from the AT published list that WWB also likes.  So I will start with those.


I was not expecting any TV stations to still be around, but cell phones towers are going up all the time and T-Mobile is making some inroads here.  Plus, I try to be legal and compliant.  Thus, also staying out of the licensed part of the duplex gap even though nobody, including EMS, seems to be using any of that block.


-Mike
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--Mike
"If you're not confused, you don't know what is going on"

Live Sound for the Mt. Shasta area
http://www.shastalivesound.com

Russell Ault

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Re: WWB vs AT-3000 Scan Groups
« Reply #3 on: June 07, 2021, 11:44:44 PM »

{...}I was not expecting any TV stations to still be around, but cell phones towers are going up all the time and T-Mobile is making some inroads here.  Plus, I try to be legal and compliant.  Thus, also staying out of the licensed part of the duplex gap even though nobody, including EMS, seems to be using any of that block. {...}

Oh shoot. I'm very sorry, there was a typo in my previous post (which I'll go fix now):

Operating those wireless microphones in the duplex gap is not legal. It is illegal. If you wish to comply with the law, do not operate those microphones in the duplex gap. The only wireless microphones that can be legally operated in the duplex gap are ones that have been designed and certified (or redesigned and recertified) to only operate on the still-legal frequencies. Older wireless microphones that just so happen to cover that range don't qualify.

Also, just to be clear, the whole point of the duplex gap is that there aren't any cellphone signals there (people more knowledgeable about cellphone technology can explain it better, but in basic terms it can be thought of as a way to prevent cell phone towers from desensing themselves), and the licensed portion of the duplex gap is reserved for licensed wireless microphone users, not LMR.

{...} I managed to find a set of frequencies from the AT published list that WWB also likes.  So I will start with those. {...}

If it were me I wouldn't bother; there's no magic to the frequencies that A-T publishes, so if you're using WWB anyway all you're doing by referring to A-T's lists is making more work for yourself.

-Russ
« Last Edit: June 08, 2021, 12:10:42 AM by Russell Ault »
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Mike Karseboom

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Re: WWB vs AT-3000 Scan Groups
« Reply #4 on: June 08, 2021, 04:53:11 PM »

Russ - thanks for the correction.  I thought I might have lucked out being "legal" but I guess not.   Where is  the ebay.mexico when you need one?


P.S.  Got you email and PM, thanks for your thoroughness.
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--Mike
"If you're not confused, you don't know what is going on"

Live Sound for the Mt. Shasta area
http://www.shastalivesound.com

Russell Ault

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Re: WWB vs AT-3000 Scan Groups
« Reply #5 on: June 08, 2021, 05:29:12 PM »

{...} I thought I might have lucked out being "legal" but I guess not.   Where is  the ebay.mexico when you need one? {...}

Selling them internationally is probably your best bet; it sounds like A-T's trade-in program ended last September (and most other manufacturers ended theirs quite a while ago).

{...} P.S.  Got you email and PM, thanks for your thoroughness.

You're welcome! I try really hard to avoid encouraging people to break the law, so when it happens by accident I feel like "thorough" is about the only way I can hope to wipe the egg off my face. :)

-Russ
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Re: WWB vs AT-3000 Scan Groups
« Reply #5 on: June 08, 2021, 05:29:12 PM »


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