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Author Topic: WWB IMD calc problem...  (Read 791 times)

Gian Luca Cavalliini

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WWB IMD calc problem...
« on: August 23, 2020, 04:31:08 am »

For what I know, WWB use IMD data in profiles just from receiving point of you.
Problem: machines (almost) not generating IMD (Sennheiser System 6000) AND others systems generating IMD...
1) System 6000 profile doesn't permit to take into account IMD from other machines
2) Other Machines take into account non relevant IMD from System 6000...

Is that correct?
How is best way to operate in this case?

Thanx

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Gian Luca Cavalliini

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Re: WWB IMD calc problem...
« Reply #1 on: August 23, 2020, 04:55:27 am »

The best I can think:

1) coordinate all IMD systems
2) FIX them
3) insert in the coordination plan "no IMD" machines with modified profiles and coordinate them not taking into account compatibility issue in the fixed coordinated frequencies.

What do you think about it? Are there better ways?

Thanx!
GLuca
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Ike Zimbel

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Re: WWB IMD calc problem...
« Reply #2 on: August 23, 2020, 12:45:30 pm »

The best I can think:

1) coordinate all IMD systems
2) FIX them
3) insert in the coordination plan "no IMD" machines with modified profiles and coordinate them not taking into account compatibility issue in the fixed coordinated frequencies.

What do you think about it? Are there better ways?

Thanx!
GLuca
I'm not totally sure I'm following you here, but what I think your main issue is whether IMD, from, say, PSM-1000's, can land on frequencies allocated to the Sennheiser 6000. The answer is "yes, they can", and that can create problems. I think the best practical approach is to band plan the two so they are as far apart as possible in the spectrum you are using. And, this may seem counter-intuitive, but you then want to coordinate your IMD producing transmitters fairly close together, say as close as 400-450 KHz apart, and up from there. I routinely put 8 IEM's in one 6 MHz TV channel. Why? because the IMD products are going to land above and below the range that you've allocated them in. So, for example, if you have IEM-1 at 500.000 MHz and IEM-8 at 506.000 MHz, you're going to have IMD's at 494.000 and 512.000 MHz. Spacing your IEM's further apart is going to push those IMD's further out-of-band.
I'm not familiar enough with WWB to give you advice on how to deal with this directly in WWB, but this gives you an idea of the basic issues in play.
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Don Boomer

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Re: WWB IMD calc problem...
« Reply #3 on: August 23, 2020, 12:53:46 pm »

Some good graphics here to help explain the idea of clustering to avoid IMD.

https://www.rfvenue.com/blog/configuring-mics-ears-together-part-2
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Jason Glass

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Re: WWB IMD calc problem...
« Reply #4 on: August 23, 2020, 01:35:52 pm »

For what I know, WWB use IMD data in profiles just from receiving point of you.
Problem: machines (almost) not generating IMD (Sennheiser System 6000) AND others systems generating IMD...
1) System 6000 profile doesn't permit to take into account IMD from other machines
2) Other Machines take into account non relevant IMD from System 6000...

Is that correct?
How is best way to operate in this case?

Thanx

It's my understanding that WWB6 is a bit more sophisticated than IAS in this regard.  In WWB6, you can open Tools > Equipment Profiles, then select a Manufacturer/Model/Band, then click the Filtering & Intermods tab.  Unchecking Intermod Source check box allows the algorithm to ignore calculated IMD products emitted by this Manufacturer/Model/Band if the user doesn't expected it to generate significant noise while still having it avoid frequencies where other devices are expected to emit IMD products.  In the example below, I made my own custom model for EM6000 bands.  I have done this for many digital models, which I use when forced into giant channel-count coordinations where taking chances like this are necessary.  IMHO, it's sometimes a better option than Robust/Standard/More Frequencies or globally deselecting different IMD orders.

« Last Edit: August 23, 2020, 01:41:05 pm by Jason Glass »
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Jason Glass

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Re: WWB IMD calc problem...
« Reply #5 on: August 23, 2020, 01:36:34 pm »

Some good graphics here to help explain the idea of clustering to avoid IMD.

https://www.rfvenue.com/blog/configuring-mics-ears-together-part-2

What a great blog post!  So clear and concise.

Gian Luca Cavalliini

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Re: WWB IMD calc problem...
« Reply #6 on: August 23, 2020, 04:42:51 pm »

Thanx all!

Ike and Don, I know "clustering" tecnique to limit the extension of IMD but... not enough space for the number of frequency in use in this case and the loss of "free space". Only thing I can do is separate tx and rx ranges with inclusion function in WWB.

All systems are requested to move in a big open space in Italy, tons of DVB-T (8MHz), not so much free space... TV events, I can't go wrong.
I've done past years similar events with different setup, but not all systems had to move everywhere, so I'd like to be prudent.
BTW in Italy things are moving for 5G, phone companies are allowed to test in the 700 MHz range, so I'd like to limit range in use above 694MHz.

Jason, I also made a lot of custom profiles in WWB... so bad I've never noticed "Intermod source" button!!!
Thanx!  :D
I think this could be the right way to do, maybe with a bit more conservative spacing to receiving IMD for System 6000 (most of them will move in the entire Arena, more than 100 metres long - no audience inside).

Thank again to all and, as usual, be patient with my not so good english language  ::)

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Jordan Wolf

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Re: WWB IMD calc problem...
« Reply #7 on: August 24, 2020, 10:59:31 pm »

So, in WWB you are looking to (1) have the System 6000 units considered non-IMD-generating and (2) have the other systemsí IMDs be calculated against the System 6000 frequencies?

You might be able to use two zones in WWB - one for all devices EXCEPT the System 6000 units and one for ONLY the System 6000 units.

Check the Channel-to-Channel and Channel-to-Intermod boxes for the IMD-Generating Devices zone as referenced to the System 6000 zone. This should have IMD products considered for the IMD-Generating Devices zone with respect to the System 6000 zone.

I hope that makes sense and I didnít misunderstand the question.
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Gian Luca Cavalliini

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Re: WWB IMD calc problem...
« Reply #8 on: August 25, 2020, 03:31:57 am »

You might be able to use two zones in WWB - one for all devices EXCEPT the System 6000 units and one for ONLY the System 6000 units.

Check the Channel-to-Channel and Channel-to-Intermod boxes for the IMD-Generating Devices zone as referenced to the System 6000 zone. This should have IMD products considered for the IMD-Generating Devices zone with respect to the System 6000 zone.

I hope that makes sense and I didnít misunderstand the question.

Thanx Jordan!
I'm already using 3 "real" zones in this case and that could be a bit confusing... But that's also a good way to go :-)
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Jordan Wolf

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Re: WWB IMD calc problem...
« Reply #9 on: August 25, 2020, 08:46:43 am »

Thanx Jordan!
I'm already using 3 "real" zones in this case and that could be a bit confusing... But that's also a good way to go :-)
Just figured Iíd put it out there if you hadnít yet considered it.
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Re: WWB IMD calc problem...
¬ę Reply #9 on: August 25, 2020, 08:46:43 am ¬Ľ


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