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Shure ua844 antenna distribution with passive shark fins


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I was helping a friend with his shure wireless system at an installed location. UA844 antenna distribution with 4x SLX4 receivers. He was having some reception issues using stock antennas and i gathered it was the location of the receivers. i offered to let him try my zaxcom bluefins on short bnc cables for better reception. If it will work he could invest in ua874 active fins. It hit me though will there be any issues with passive blue fins on a 12v active antenna cable line or should they work for testing purposes and bypass any power on the line?

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13 hours ago, osa said:

I was helping a friend with his shure wireless system at an installed location. UA844 antenna distribution with 4x SLX4 receivers. He was having some reception issues using stock antennas and i gathered it was the location of the receivers. i offered to let him try my zaxcom bluefins on short bnc cables for better reception. If it will work he could invest in ua874 active fins. It hit me though will there be any issues with passive blue fins on a 12v active antenna cable line or should they work for testing purposes and bypass any power on the line?

If there isn’t a capacitor to block the 12v in the antenna it definitely could damage them. Not sure if zax puts them in their fins or not. I know Lectro puts them in the SNA600a now to prevent damage from an accidental power application.

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19 hours ago, Trey LaCroix said:

If there isn’t a capacitor to block the 12v in the antenna it definitely could damage them. Not sure if zax puts them in their fins or not. I know Lectro puts them in the SNA600a now to prevent damage from an accidental power application.

Great thank you glad i checked here. I checked with Glenn and he also advised against it. He mentioned there is a 50ohm resistor that could possibly burn out if power is applied. I am going to remote via short low loss cables his stock antennas for now and advise he purchase the ua874 active fins. 

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1 hour ago, osa said:

Great thank you glad i checked here. I checked with Glenn and he also advised against it. He mentioned there is a 50ohm resistor that could possibly burn out if power is applied. I am going to remote via short low loss cables his stock antennas for now and advise he purchase the ua874 active fins. 

I used to use the ua874's and never had issues until I was outside in the rain. I only used them when remoting over long distances. I kept them dry but was having really bad RF/electrical noise when we would move them during the take to keep up with talent. My boom op at the time said that the Shures should really be thought of as installation antennas for live sound. This was of course well before the new Shure Axient system and I'm sure their new gear is more robust for production sound. Also, this was not a scientific test of any kind. However, I switched to the Lectro ALP690s and have not had the issue again. Just 2 cents.

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  • 2 weeks later...

Wanted to report back I ended up machining some brackets for the stock ua874 whip antennas for my friend, mounting them up high on mic stands with 10ft low loss 50ohm bnc in line of sight for transmitters and it made a world of difference. After this setup i realized the sharkfins might have been overkill. But for reference the passive zaxcom original bluefins do have a 50ohm resistor that could be potentially damaged by power, according to my discussion with Glenn so it is best to avoid powered distribution with passive antennas, unless you are using passive antennas specifically designed to block 12v power. 

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