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Author Topic: Combining Digital and Analog Wireless  (Read 397 times)

Mark Hannah

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Combining Digital and Analog Wireless
« on: November 14, 2017, 04:55:25 pm »

Based on the AES seminar descriptions, I missed out on a lot of knowledge about RF.  So here I come to ProSoundWeb!  Again...

In general, I'm looking for guidance and best practice when working with digital and analog wireless together.

More specific...
1) If you need to squeeze a lot of digital RF into a coordination, how many MHz would separate the digital and analog before being comfortable turning off 5tx and 3x3 IMD tests?  I know the mics will function fine with only 500KHz spacing.  Best if 600KHz.
2) If you know your digital mics' CNR is 11 dB and have a low level DTV, do you risk coordinating on top of it?

Thank you...
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Ike Zimbel

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Re: Combining Digital and Analog Wireless
« Reply #1 on: November 14, 2017, 05:06:59 pm »

Based on the AES seminar descriptions, I missed out on a lot of knowledge about RF.  So here I come to ProSoundWeb!  Again...

In general, I'm looking for guidance and best practice when working with digital and analog wireless together.

More specific...
1) If you need to squeeze a lot of digital RF into a coordination, how many MHz would separate the digital and analog before being comfortable turning off 5tx and 3x3 IMD tests?  I know the mics will function fine with only 500KHz spacing.  Best if 600KHz.
2) If you know your digital mics' CNR is 11 dB and have a low level DTV, do you risk coordinating on top of it?

Thank you...
Yes, that was a good panel, a lot of good information there. WRT #2, yes you can. For example, on an awards show this past summer, outdoors, the guitar tech for a BIG BAND called me over to look at his rig because he was seeing some activity on the bottom LED on his ULXD-4. My scan that I had imported into IAS showed a slight increase in the noise floor in that area and a double check with my TTi confirmed that we were on top of a very low level DTV channel (around -90 dbu). I showed this to the tech, had him turn on one of his packs and showed him the difference between his signal and the noise floor. He was satisfied with the explanation and their performance came off just fine.
« Last Edit: November 16, 2017, 10:02:29 pm by Ike Zimbel »
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~Ike Zimbel~
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Henry Cohen

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Re: Combining Digital and Analog Wireless
« Reply #2 on: November 15, 2017, 08:18:40 am »

1) If you need to squeeze a lot of digital RF into a coordination, how many MHz would separate the digital and analog before being comfortable turning off 5tx and 3x3 IMD tests?  I know the mics will function fine with only 500KHz spacing.  Best if 600KHz.

This depends on the design of the respective wireless systems and the analog system's selectivity as well as linearity. The analog system will always have the potential for creating IM products in the transmitters, and the antenna multicoupler(s) for the digital wireless will likely have a potential for IM creation as well. Thus, you need to approach IM avoidance for a mixed environment in the same manner as an all analog environment.


Quote
2) If you know your digital mics' CNR is 11 dB and have a low level DTV, do you risk coordinating on top of it?
Ostensibly yes, but you have to leave enough link budget above the noise floor for mic transmitter signal attenuation as the talent moves about the performance area. Simply having the talent turn so their body is between the TX and RX antennas can cause a 40dB drop in signal level reaching the RX antenna.
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Henry Cohen

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John Daniluk (JD)

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Re: Combining Digital and Analog Wireless
« Reply #3 on: November 21, 2017, 02:56:26 pm »

one of the issues that I have run into when using analog with digital devices is the delay with the digital devices.   If you have one person using an analog wireless standing close to a person with a digital wireless you may notice some delay.  It will sound like a delay processor very low in the mix.   

jd
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