OT antenna splitter

[Andy Follett]

This is way OT but didn't see anything on the web that would help.

I have 10 sennheiser G3 iem systems in use. All the antennas are the little 4" or so stock ones that came with them and are less than an inch away from each other in the back of the rack - not ideal but it works - for the most part.

My problem is the guy(s) standing closest to the rack, usually me, gets pops, static, etc. thru the iems - unless I find a sweet spot and don't move. The guys 10' or more from the rack/antenna "farm", experience pretty much no problems or they put the pack on the other side of their belt and the problem is solved. I need to be near the rack to run the board and such otherwise the stupid simple answer is just move 10' away from the rack.

Sennheiser makes a splitter solution for $925 that will power and combine 4 iems units/antennas. I already built a power supply that powers all 10 with a wiring harness so I really don't care about the power.

Does anyone have any experience with a "generic" splitter that might fit as a solution. Spending nearly 3K on three of those units..... ouch. Maybe a radio shack (TV) antenna splitter(s) into one of those splitter units would work all 10???

I appreciate any insight.

[Butch Bos]

They are transmitters not receivers like wireless mics so NO the radio shack stuff will NOT work and that is why the Sennheiser units are expensive

You might try removing the antenna from YOUR receiver that will drop the sensitivity on it by about half

Butch

[cgrafx]

This is way OT but didn't see anything on the web that would help.

I have 10 sennheiser G3 iem systems in use. All the antennas are the little 4" or so stock ones that came with them and are less than an inch away from each other in the back of the rack - not ideal but it works - for the most part.

My problem is the guy(s) standing closest to the rack, usually me, gets pops, static, etc. thru the iems - unless I find a sweet spot and don't move. The guys 10' or more from the rack/antenna "farm", experience pretty much no problems or they put the pack on the other side of their belt and the problem is solved. I need to be near the rack to run the board and such otherwise the stupid simple answer is just move 10' away from the rack.

Sennheiser makes a splitter solution for $925 that will power and combine 4 iems units/antennas. I already built a power supply that powers all 10 with a wiring harness so I really don't care about the power.

Does anyone have any experience with a "generic" splitter that might fit as a solution. Spending nearly 3K on three of those units..... ouch. Maybe a radio shack (TV) antenna splitter(s) into one of those splitter units would work all 10???

I appreciate any insight.

You not looking for a Splitter your looking for a combiner. Yes the are expensive. The 4 channel one for my Shure PSM 900s was $1800, and the 8 channel version runs $3800. They do help, both with improved signal performance and reduced clutter. In my case, it reduced 4 antenna's to one. I've also just purchased a separate high-gain antenna that can be stand mounted for better position if needed.

[Naturally Digital]

I would start by checking your frequency coordination. What are you using to come up with your frequencies? You need to make sure you have a proper coordination otherwise you could have intermods that are causing problems like that, especially when you're standing next to the rack. The closer together all the antennae are, the worse the intermods. One option is to physically separate the transmitters. That might help a bit.

Once you know you have a solid coordination, you could try dropping the transmit power on the units. IIRC those have a high and low setting (100mw and 10mw perhaps). I could be wrong but it's something to look for.

There's a possibility that all those tx frequencies in close proximity (antennae locations) are summing in the air and overloading the receiver front end in your pack. Especially if all your freqs are close together in the spectrum. 10 channels is a lot to try and operate in the manner you're doing (without the active tx combiners and a single antenna). I know you likely don't want to, but one of your cheapest and simplest options might be to physically locate the tx units in different places around the stage.

If the antennae are 'buried' in the back of the rack, the problems will be worse because of the multipath interference bouncing around in the rack. On the cheap you could make something that moves the antennae out of the rack or to the top/back of the rack etc. A little panel with pass-through BNC connectors and short cables to the tx units, then you mount the little antennae to the panel.

If you go the active route, this is the first kit to purchase.

If you ever need to split antennae passively (for use with receivers, not IEMs) then don't go to Radio Shack, look for these units.

What you're experiencing is a bit of a common problem when standing close to the tx units.

Drop back in and let us know if you improve things. Good luck!

[Andy Follett]

I'm using the software that came with Sennheiser iems to manage the frequencies. My mics and iems are all networked together. Doesn't seem to matter about resetting the freqs when it comes to the pops. I'll check into the reducing the power setting on my iem - if there's a setting for it in the software. That sounds like a great idea. Anyone know offhand (read without me looking) where/if there is a setting for that?

I'll also look into the short bnc's to a antenna "panel" in the back. Thanks for the suggestion.

I've worked hard to get my two rack cases as organized and compact as possible so relocating half the rack to the other side of the "stage" is just not a viable option at this point. Trailer space, running snakes, plugging feeds in/out at every gig... "nothing can go wrong". Currently all my vocal mics, iems, and gtr are wireless. One 8 channel snake for the drums/bass and I'm up and running. A few extra runs when I have horn players or keys or whatever.

We get a stage about 1/2 of the time at a gig. The rest of the time it's an area in a corner or whatever in a banquet room. I don't have the manpower or time to manage the logistics for another rack in a separate location. I'll put up with the pops if I have to vs. that scenario.

Thanks for the replies.

[Andy Follett]

No settings in the software but you can set the "RF Power" on the transmitter with the menu on the front panel. High or Low are the choices. I set it to Low - I'll let you know if it helps.

[tartan]

I realize this topic is about combiners, but here's a great video on splitting signals, DIY. It may get you thinking in the right direction for combining.

https://www.youtube.com/watch?v=SH3VKHcwDj0


BTW, Mipro has 470~960MHz combiners for IEM transmitters:
http://avlex.com/product_categories/...tenna_systems/


Josh

[RBIngraham]

I realize this topic is about combiners, but here's a great video on splitting signals, DIY. It may get you thinking in the right direction for combining.

https://www.youtube.com/watch?v=SH3VKHcwDj0


BTW, Mipro has 470~960MHz combiners for IEM transmitters:
http://avlex.com/product_categories/...tenna_systems/


Josh

No you can not take a simple passive spliter and use that to combine multiple RF outputs into a single antennae. Combining is a lot more complex than simple splits, it requires that you filter out the outputs from other transmitters so it doesn't get into the output stage of the transmitter. So for example if you have four transmitters the connection to trans #1 needs to filer out the output from Trans #2-4.

I don't understand the process to explain it any better but my father, the long time amateur radio guy, explained it to. It's basically the same technology they use for a radio repeater where they have a receiver and transmitter connected to a single antenna.

[RBIngraham]

More than likely what is happening is not that the RF output from your transmitter is too high or too weak. Most likely the front end of the receiver on your beltpack is being desensitized by all the incoming RF signals since you are very close to all the transmitters. The output from your transmitter could be overloading the RF input I guess but I suspect the front end on the beltpack receiver just isn't good enough to filter out all the noise. In this case the noise being all the other 9 transmitters that it's trying to filter out.

If your transmitter is overloading the RF input on your receiver another solution might simply be to buy a single piece of coax cable and just remote your own antennae to the other side of the stage. That puts your transmit antennae further away from you but doesn't require very much expense or a ton of work. Leave all the others alone. That is probably the first thing I would try really.


If your receiver is just being overloaded by all the "noise" from the other IEM sets then a better solution might be to put everyone else's transmitter on low power, not your transmitter. If this is the problem lowering your signal (your transmitter's output) is just going to make the noise floor (others' transmitters) even worse and likely make the issue worse. If this is the problem even an antennae combiner likely wouldn't solve the issue, you're pack's RF front end would still be overwhelmed, you would just have a neater set up. Although you could then remote the transmit antennas further away I guess and not have a giant cluster of RF energy all in one place, which should help some.

[tartan]

No you can not take a simple passive spliter and use that to combine multiple RF outputs into a single antennae. Combining is a lot more complex than simple splits, it requires that you filter out the outputs from other transmitters so it doesn't get into the output stage of the transmitter. So for example if you have four transmitters the connection to trans #1 needs to filer out the output from Trans #2-4.

I don't understand the process to explain it any better but my father, the long time amateur radio guy, explained it to. It's basically the same technology they use for a radio repeater where they have a receiver and transmitter connected to a single antenna.

Oh ya ya -- I wasn't suggesting that a passive splitter could get the job done for combining. I spent my early career in the days when cablemodems had downstream (input) and upstream (output) connections wired to two, separate jacks. So we had to install what was called a diplex filter along with the cablemodem, to separate the different frequency space using by the up- and down-streams. So the same thing *kinda* applies here. It just gets really complicated with 10 wireless IEMs on stage.