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[Kevin Maxwell]

New IEM system added to church.

A church that I have been helping out with their tech needs for a while, wants to change to some IEMs for their singers. They have been playing with a couple of Shure PSM 300 pro systems and want to have a total of 7 of them.

The transmitters will be in a closet backstage and I want to use an antenna combiner and run coax out to the stage area which should be a run of less than 25feet. I was thinking of one 8way combiner but the cost of one of them is a lot more expensive than 2 - 4way combiners and 2 antennas especially the Shure PA411 compared to the PA821B. Is the 8way really needed and is it really worth the extra money? I was thinking of one PA805 directional antenna or 2 of them if I use the PA411 4 way combiner. How close can 2 of these antennas used for IEM transmitters be to each other?

The receivers for their wireless mics are in the same closet as the amps for the system. The amp rack is about 6 feet tall and full, the DSP and wireless rack is about 3 feet tall the 2 racks are 90degees out from each other. There are antenna distros for the receivers and 2 antennas out above the stage. This has all worked just fine. And they have a bunch of wireless mics thru out their building. I just ran a Wireless Work Bench test to see if their current configuration can coexist with 8 new channels of IEM and it looks like a lot of the mics will need to be retuned to make this all work but it can work. I also took into account the loss of most of the 600MHz band but I didn’t take into account the repack down in 500MHz. But form what I have seen this area don’t look like it will be impacted much by that. 

I was going to put another wooden rack on top of the 3 foot wireless mic receives rack with the new IEM transmitters on the top end of the new rack. There will be an X32 Rack at the bottom of the new rack. The wireless mic receivers and the IEM transmitters should be at least 12 rack spaces apart. Is this far enough apart? I was thinking of putting a metal rack shelf at the bottom of this new rack for a little help with isolation. 

Any words of caution or is anything wrong with my plan? Thank you for any help you can be.

[Jerome Malsack]

1/4 wave separated is optimum  so 8 inch to 24 inch is beyond the 1/4 wave depending on the frequencies used.  Same is true if the receivers are near by.  Another point on the antenna is that some like to use the helical antenna.  This works for both polarizations, horizontal and vertical.  preventing dropouts.
The RF Venue  CP Beam is one of these  https://www.rfvenue.com/products/cp-beam   

You may also find that the prices are better. 

[Ike Zimbel]

New IEM system added to church.

A church that I have been helping out with their tech needs for a while, wants to change to some IEMs for their singers. They have been playing with a couple of Shure PSM 300 pro systems and want to have a total of 7 of them.

The transmitters will be in a closet backstage and I want to use an antenna combiner and run coax out to the stage area which should be a run of less than 25feet. I was thinking of one 8way combiner but the cost of one of them is a lot more expensive than 2 - 4way combiners and 2 antennas especially the Shure PA411 compared to the PA821B. Is the 8way really needed and is it really worth the extra money? I was thinking of one PA805 directional antenna or 2 of them if I use the PA411 4 way combiner. How close can 2 of these antennas used for IEM transmitters be to each other?

The receivers for their wireless mics are in the same closet as the amps for the system. The amp rack is about 6 feet tall and full, the DSP and wireless rack is about 3 feet tall the 2 racks are 90degees out from each other. There are antenna distros for the receivers and 2 antennas out above the stage. This has all worked just fine. And they have a bunch of wireless mics thru out their building. I just ran a Wireless Work Bench test to see if their current configuration can coexist with 8 new channels of IEM and it looks like a lot of the mics will need to be retuned to make this all work but it can work. I also took into account the loss of most of the 600MHz band but I didn’t take into account the repack down in 500MHz. But form what I have seen this area don’t look like it will be impacted much by that. 

I was going to put another wooden rack on top of the 3 foot wireless mic receives rack with the new IEM transmitters on the top end of the new rack. There will be an X32 Rack at the bottom of the new rack. The wireless mic receivers and the IEM transmitters should be at least 12 rack spaces apart. Is this far enough apart? I was thinking of putting a metal rack shelf at the bottom of this new rack for a little help with isolation. 

Any words of caution or is anything wrong with my plan? Thank you for any help you can be.

If you are remoting all of the antennas, the proximity of the TX and RX units in the rack is not an issue, BUT, make sure you use good quality BNC cable. Typically the cable that Shure sells will be fine, just don't buy cheap crap on Amazon.
WRT the PA411 combiners, see this note from the Shure sitehttp://www.shure.com/americas/support/find-an-answer/pa411-units-combining-the-rf-outputs

[Kevin Maxwell]

1/4 wave separated is optimum  so 8 inch to 24 inch is beyond the 1/4 wave depending on the frequencies used.  Same is true if the receivers are near by.  Another point on the antenna is that some like to use the helical antenna.  This works for both polarizations, horizontal and vertical.  preventing dropouts.
The RF Venue  CP Beam is one of these  https://www.rfvenue.com/products/cp-beam   

You may also find that the prices are better.

Thank you for your reply. I was looking at the RFVenue stuff and I don’t feel in this application a Helical Antenna is needed. The distance from antenna to receivers shouldn’t be more then about 35feet with a clean line of sight to their backs where the receivers will be.

[Kevin Maxwell]

If you are remoting all of the antennas, the proximity of the TX and RX units in the rack is not an issue, BUT, make sure you use good quality BNC cable. Typically the cable that Shure sells will be fine, just don't buy cheap crap on Amazon.
WRT the PA411 combiners, see this note from the Shure sitehttp://www.shure.com/americas/support/find-an-answer/pa411-units-combining-the-rf-outputs

Thank you for your reply. I will most likely be making the cables myself, I have made a lot of them over the years. This way I can use the shortest length of cable needed to reach the antennas. I am aware that for antennas I need to use 50ohm coax. Someone gave me about half a 1000foot roll of Belden BL-1505a RG59/20 SDI coax cable in Violet. Too bad it wasn’t 50ohm stuff.  I wasn’t planning on trying to combine 2 PA411s onto the same antenna; I will just use 2 antennas. I just talked to Shure support about this whole thing and it looks like 2 PA411s make the most sense.

[Don Boomer]

Thank you for your reply. I was looking at the RFVenue stuff and I don’t feel in this application a Helical Antenna is needed. The distance from antenna to receivers shouldn’t be more then about 35feet with a clean line of sight to their backs where the receivers will be.

The issue isn’t distance, but rather it is polarty.  You do not have a diversity system as in wireless mics to protect you.  The signal from someone bending over can drop by 30 dB and any reflections off anything metal will flip polarity by 180°.  And you don’t wanna crank the power up to try to make up for it as that would cause additional IM issues for everything. 

As far as “good cables” ... I’m sure Ike is implying using double shielded (100%) coax such as RG8x or LMR-195.

[Kevin Maxwell]

The issue isn’t distance, but rather it is polarty.  You do not have a diversity system as in wireless mics to protect you.  The signal from someone bending over can drop by 30 dB and any reflections off anything metal will flip polarity by 180°.  And you don’t wanna crank the power up to try to make up for it as that would cause additional IM issues for everything. 

As far as “good cables” ... I’m sure Ike is implying using double shielded (100%) coax such as RG8x or LMR-195.

The other issue with the Helical Antenna is the look of it. I don't think I can find a place to hide it.

[Jason Glass]

Thank you for your reply. I will most likely be making the cables myself, I have made a lot of them over the years. This way I can use the shortest length of cable needed to reach the antennas. I am aware that for antennas I need to use 50ohm coax. Someone gave me about half a 1000foot roll of Belden BL-1505a RG59/20 SDI coax cable in Violet. Too bad it wasn’t 50ohm stuff.  I wasn’t planning on trying to combine 2 PA411s onto the same antenna; I will just use 2 antennas. I just talked to Shure support about this whole thing and it looks like 2 PA411s make the most sense.

Since you're making the cables yourself, create an account at Tessco and buy Belden 9913F7 by the foot for $0.87 per.  https://www.tessco.com/product/55310  It's the best deal available for the best cable for the job.  Use BNC connectors designed for LMR-400, preferably crimped style.  If you're not already well experienced in making those, own the proper tools, and are equipped and educated to conduct VNA and/or TDR testing on your cables, DO NOT MAKE THEM YOURSELF.  Take the $ hit, buy finished assemblies, and reap the benefits of support from the manufacturer.

The best deal anywhere for appropriate antennas for your described application is the Audio-Technica ATW-A49 LPDA.  https://www.audio-technica.com/cms/accessories/02531fd0511b76c3/index.html  A light coat of spray lacquer (I prefer Ace Hardware brand) in whatever color makes them most invisible in your venue will not affect performance.  Just be sure to well mask the connector before painting.

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