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Author Topic: Shure ULX-D power level  (Read 1564 times)

Helge A Bentsen

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Shure ULX-D power level
« on: February 13, 2021, 03:47:30 pm »

I've been experimenting with power levels on Shure ULX-D beltpacks lately. Most folks I run into use them at 10mW, I've been turning them down to 1mW to save batteries for long production days and it works. I can run a whole day with rehearsals in the morning and streaming in the evening on one set of batteries. IME there doesn't seem to be any more dropouts, I'm using 8-16 channels, the receivers are feed by Shure active antennas, 2x5m coax cables and cascaded internally in the rack. It's a pretty "short throw" application,  I think I'll struggle to get any belt pack more than 20m away from the antennas before I'm out of the room.

So, I'm trying to get a better understanding for setting power levels.
Are there any "hard & fast" rules to determine the "correct" power level for these beltpacks?
In what kind of applications would you choose 10mW/1mW?
Etc..


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Ike Zimbel

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Re: Shure ULX-D power level
« Reply #1 on: February 13, 2021, 03:52:32 pm »

I've been experimenting with power levels on Shure ULX-D beltpacks lately. Most folks I run into use them at 10mW, I've been turning them down to 1mW to save batteries for long production days and it works. I can run a whole day with rehearsals in the morning and streaming in the evening on one set of batteries. IME there doesn't seem to be any more dropouts, I'm using 8-16 channels, the receivers are feed by Shure active antennas, 2x5m coax cables and cascaded internally in the rack. It's a pretty "short throw" application,  I think I'll struggle to get any belt pack more than 20m away from the antennas before I'm out of the room.

So, I'm trying to get a better understanding for setting power levels.
Are there any "hard & fast" rules to determine the "correct" power level for these beltpacks?
In what kind of applications would you choose 10mW/1mW?
Etc..
One short answer I like to give on the Tx power question is "All you need is enough". If it works at 1mw in your situation, you're good.
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Brian Jojade

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Re: Shure ULX-D power level
« Reply #2 on: February 13, 2021, 04:36:42 pm »

One short answer I like to give on the Tx power question is "All you need is enough". If it works at 1mw in your situation, you're good.

Yep. That's the perfect technical explanation.

There is NO advantage of running at 10mw if 1mw is enough.

At higher power, you're simply burning through more battery power, and with higher power, you also can create other issues such as interference with other devices, overpowering your receivers, etc.

If you have problems at 1mw, try cranking up to 10mw.
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Brian Jojade

Don Boomer

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Re: Shure ULX-D power level
« Reply #3 on: February 13, 2021, 08:26:21 pm »

The way to determine how much power you'll need beforehand is to create a link budget.
https://www.rfvenue.com/blog/rf-training-session-2-distributed-antennna-systems-0-0
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Don Boomer
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Rui Lisboa

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Re: Shure ULX-D power level
« Reply #4 on: February 14, 2021, 04:52:16 am »

My experience in transitioning from analogue to digital has led me to rethink transmission power levels in absolute terms.

First because of the resilience digital devices have enduring weaker CNRs. I now tend to use less power.

Second because the PARP on digital modulation is different. For the devices I manly use (Shure AD) the PARP is 5dB. So by using it @10mW there is roughly 31,5mW peak power in transmission. This usually suffices taking into account a properly designed system by effectively doing a link budget.
I really don't recall using analogue systems @30mW that often specially in larger venues doing TV shows manly because a lot of older systems were fixed on 50mW.

I don't know ULXD's PARP but 1mW always leaves me a bit edgy specially on longer recordings and reality TV as there is usually a lot of absorption from the body going on. Although measures are usually taken to prevent isolation of the antenna from the body or damp clothes a short on the antenna might bring unpleasant surprises probably to a higher extent than bothering talents to change a battery once more.
The batteries on Shure's products are very well designed. We usually push the ADX1 to more than 8,5 hours @10mW. So usually we leave it at 10.
I still find amazing how this was achieved as there are other brilliant systems on the market that have a modulation scheme with lower PARP that end up being less effective on battery duration with similar transmission power levels.


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Henry Cohen

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Re: Shure ULX-D power level
« Reply #5 on: February 14, 2021, 12:52:14 pm »

My experience in transitioning from analogue to digital has led me to rethink transmission power levels in absolute terms.

First because of the resilience digital devices have enduring weaker CNRs. I now tend to use less power.

Second because the PARP on digital modulation is different. For the devices I manly use (Shure AD) the PARP is 5dB. So by using it @10mW there is roughly 31,5mW peak power in transmission. This usually suffices taking into account a properly designed system by effectively doing a link budget.
I really don't recall using analogue systems @30mW that often specially in larger venues doing TV shows manly because a lot of older systems were fixed on 50mW.

I don't know ULXD's PARP but 1mW always leaves me a bit edgy specially on longer recordings and reality TV as there is usually a lot of absorption from the body going on. Although measures are usually taken to prevent isolation of the antenna from the body or damp clothes a short on the antenna might bring unpleasant surprises probably to a higher extent than bothering talents to change a battery once more.
The batteries on Shure's products are very well designed. We usually push the ADX1 to more than 8,5 hours @10mW. So usually we leave it at 10.
I still find amazing how this was achieved as there are other brilliant systems on the market that have a modulation scheme with lower PARP that end up being less effective on battery duration with similar transmission power levels.

"PARP"? I think you might mean PAPR, Peak to Average Power Ratio (maybe a language translation thing)? I'm not certain, but I don't believe PAPR has much relevancy in a single carrier system, such as that used in digital wireless microphones (be it Shure, Sennheiser, Zaxcom or anybody else's). PAPR is a metric usually applied to multi-carrier transmission schemes such as LTE in which there are multiple subcarriers and it's important to know the average subcarrier peak power as compared to the overall composite power level witihn the emissions mask (e.g. OFDM). How did you arrive at 5dB for the AD?

In a single carrier digital emissions system, it is important to know the mean power level; that power spread across the occupied channel bandwidth (165kHz in the case of the ULXD).
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Rui Lisboa

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Re: Shure ULX-D power level
« Reply #6 on: February 14, 2021, 01:32:03 pm »

Indeed Henry did not notice the acronym was misspelled. Thinking in a different language.
All the manufacturers I have spoke with have been very convincing stating PAPR (got it right this time  8)) on a digital transmission leads to peak power numbers similar to the sum of TX power + PAPR's equivalent on analogue.
Shure's numbers might be checked with themselves.
Either way I've had this conversation with the manufacturers (Lectrosonics and Shure) and was told PAPR is indeed relevant on single carrier transmission.


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Henry Cohen

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Re: Shure ULX-D power level
« Reply #7 on: February 14, 2021, 01:54:53 pm »

Indeed Henry did not notice the acronym was misspelled. Thinking in a different language.

No problem. Thought that might be the case,


Quote
All the manufacturers I have spoke with have been very convincing stating PAPR (got it right this time  8)) on a digital transmission leads to peak power numbers similar to the sum of TX power + PAPR's equivalent on analogue.
Shure's numbers might be checked with themselves.
Either way I've had this conversation with the manufacturers (Lectrosonics and Shure) and was told PAPR is indeed relevant on single carrier transmission.

So it sounds like the conundrum the OEM's have been facing when trying to explain relative performance between digital and analog systems in terms of RF power. I don't think the original purpose of PAPR was intended for this, since it's used for defining an attribute within a single system (not as a comparison between disparate systems types), but it may be the best existing term, though I think a better term would be PEPR; Peak to Envelope Power Ratio, as it's the envelope power of the digital channel as compared to the unmodulated CW carrier of an analog FM carrier.
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Henry Cohen

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Rui Lisboa

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Re: Shure ULX-D power level
« Reply #8 on: February 14, 2021, 02:09:54 pm »

PEPR. That makes all the sense!
Either way stating power equivalencies between analogue and digital is telling a tenth of the story. The behaviour of the digital systems specially on RF populated environments namely in high channel counts makes me eager to prepare each new project going the digital route.
Even systems such as the SLXD that are peaked @10mW seem to cover unthinkable areas with small battery consumption (for a digital system).
SLXD and ULXD are not true diversity, they`re receiver sensitivity and possibly error correction are not on par with top tier systems and they still work brilliantly @10mW.
And they're batteries last more time on set without a break than my stomach and ears.
« Last Edit: February 14, 2021, 02:22:07 pm by Rui Lisboa »
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Helge A Bentsen

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Re: Shure ULX-D power level
« Reply #9 on: February 14, 2021, 02:34:11 pm »

The way to determine how much power you'll need beforehand is to create a link budget.
https://www.rfvenue.com/blog/rf-training-session-2-distributed-antennna-systems-0-0

Great video, thanks  :)

I "think" I have a better understanding for selecting power levels now, there was a lot of new things to digest in that video.
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ProSoundWeb Community

Re: Shure ULX-D power level
« Reply #9 on: February 14, 2021, 02:34:11 pm »


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