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Author Topic: 900MHz Band IEM Combining  (Read 373 times)

Craig Swoverland

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900MHz Band IEM Combining
« on: May 21, 2021, 01:26:15 PM »

Hello. New member. New to Wireless IEM. I am not an expert, and I am looking for guidance. :)

I have 3 units VocoPro (IEM-Digital) that operate on the 900MHz band. These units are simply installed in the rack with our mixer (XR18) and an amp for our subs, and we're utilizing the built-in antennae on each unit. In our rehearsal space, the units seem to be working well, however, we have had *some* dropouts. My research (which includes quite a bit of content from this forum and other places) leads me to believe that we could better our setup by adding a combiner and using a single antenna.

With regards to combiners, I understand that Shure, Sennheiser, RF Venue make products for this purpose, however, they are pricey and may or may not support the 900Mhz band. I am a tech dude by trade, so I have an uncontrollable urge to research and find out if I can "do it cheaper".

Without considering cables and connectors (which I assume I can plan to move from BNC to COAX to N or SMA etc) I have identified some solutions for passive combining on the 900Mhz band, and I am looking for your good guidance on whether my analysis is on point, or if I am completely misguided. My proposed solution is:

Combiner: Ebay has several used PASSIVE combiners for sale which seem to support the 900 band. Is passive OK for an IEM application?
Example: https://www.anixter.com/en_la/product-detail.OC-8D-BLONDER-TONGUE.169871.html


With regards to antenna, I have seen wideband and focused 900Mhz antennae for sale.  I do not understand everything about this market segment either. I have found this:
https://www.arcantenna.com/products/laird-pac-wireless-od9-5890-950-mhz-5-dbi-low-cost-outdoor-fiberglass-omni-antenna-with-n-female-connector

I know the Shure systems usually promote a more directional antenna, but some of my research indicated that in many cases (with smaller stages etc) an omnidirectional antenna can be more appropriate. Any input on this topic?

I figure that I could either use a spare cymbal or Mic Stand to mount the antenna and get it up in the air a bit, or perhaps add functionality to my rack (hardware on the side) to mount the antenna when in use.


Can anyone speak to the approach I am taking here? Am I on the right track with regards to the combiner and antenna, or am I totally missing something? I know that there will be some cost in getting my patch cables from the 6-8 BNC connectors on my VocoPro units to F inputs on the combiner, and then some conversion from F out of the combiner to whatever connector the antenna uses. Anything I need to be wary of in this regard?

Thanks in advance for any input you might be able to provide.


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Mac Kerr

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« Reply #1 on: May 21, 2021, 01:38:11 PM »

Hello. New member. New to Wireless IEM. I am not an expert, and I am looking for guidance. :)

Thanks in advance for any input you might be able to provide.

Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules displayed in the header at the top of the section, and in the Site Rules and Suggestions in the Forum Announcements section, and on the registration page when you registered.

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Craig Swoverland

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Re: 900MHz Band IEM Combining
« Reply #2 on: May 21, 2021, 01:42:22 PM »

Done deal. Thanks. (Now I feel foolish) :)
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Henry Cohen

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Re: 900MHz Band IEM Combining
« Reply #3 on: May 21, 2021, 06:33:51 PM »

Hello. New member. New to Wireless IEM. I am not an expert, and I am looking for guidance. :)

I have 3 units VocoPro (IEM-Digital) that operate on the 900MHz band. These units are simply installed in the rack with our mixer (XR18) and an amp for our subs, and we're utilizing the built-in antennae on each unit. In our rehearsal space, the units seem to be working well, however, we have had *some* dropouts. My research (which includes quite a bit of content from this forum and other places) leads me to believe that we could better our setup by adding a combiner and using a single antenna.

With regards to combiners, I understand that Shure, Sennheiser, RF Venue make products for this purpose, however, they are pricey and may or may not support the 900Mhz band. I am a tech dude by trade, so I have an uncontrollable urge to research and find out if I can "do it cheaper".

Without considering cables and connectors (which I assume I can plan to move from BNC to COAX to N or SMA etc) I have identified some solutions for passive combining on the 900Mhz band, and I am looking for your good guidance on whether my analysis is on point, or if I am completely misguided. My proposed solution is:

Combiner: Ebay has several used PASSIVE combiners for sale which seem to support the 900 band. Is passive OK for an IEM application?
Example: https://www.anixter.com/en_la/product-detail.OC-8D-BLONDER-TONGUE.169871.html


With regards to antenna, I have seen wideband and focused 900Mhz antennae for sale.  I do not understand everything about this market segment either. I have found this:
https://www.arcantenna.com/products/laird-pac-wireless-od9-5890-950-mhz-5-dbi-low-cost-outdoor-fiberglass-omni-antenna-with-n-female-connector

I know the Shure systems usually promote a more directional antenna, but some of my research indicated that in many cases (with smaller stages etc) an omnidirectional antenna can be more appropriate. Any input on this topic?

I figure that I could either use a spare cymbal or Mic Stand to mount the antenna and get it up in the air a bit, or perhaps add functionality to my rack (hardware on the side) to mount the antenna when in use.

Can anyone speak to the approach I am taking here? Am I on the right track with regards to the combiner and antenna, or am I totally missing something? I know that there will be some cost in getting my patch cables from the 6-8 BNC connectors on my VocoPro units to F inputs on the combiner, and then some conversion from F out of the combiner to whatever connector the antenna uses. Anything I need to be wary of in this regard?

First, if you're operating this equipment in the US, it seems this unit is not in fact certified by FCC, which means it's not legal to operate in the US. If you can find an FCC ID No. on a label o the base transmitter, post it and I can look it up.

Secondly, from what I can see this unit operates in the 902-928 MHz ISM band, so any peripheral equipment you're considering must cover this frequency range.

As for active vs passive combining, active is definitely be better [when done correctly]. The RF Venue Combine4 is very reasonably  priced for it's features/performance and operates past 930MHz. Conversely, if you can tolerate the ~5dB loss of a passive 3-way combiner, this Mini-Circuits 3-way splitter/combiner is an excellent option (will likely need adapters for the connectors). The Blonder Tongue unit you link to is an 8-way passive and has over 11dB of insertion loss, which would be very detrimental.

As for the antenna, it's a question of the coverage pattern you need. If you need 360 degree, or thereabouts, coverage about the antenna, then an omni is the best choice. Higher gain can be better if you can give up vertical beamwidth. If OTOH, your antenna is off to one side with respect to the desired coverage area, a directional antenna is preferred as it will focus (to a certain degree) the RF energy where it's required. Lot's of options for both types. 
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Henry Cohen

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ProSoundWeb Community

Re: 900MHz Band IEM Combining
« Reply #3 on: May 21, 2021, 06:33:51 PM »


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