Sennheiser wireless remote antennas

Bgarrett74

Bgarrett74

Member
Hello,
I own 15 evolution ew300 g3 Sennheiser wireless systems with countryman H6 headsets. I also own 10 evolution ew100 g3. I use them together for musicals. I recently have been having issues with RF interference. I have the A band frequency. 516-558. I have to put the receivers at FOH. The throw distance is about 70'. I have two racks of ten with the original antennas on them. They are all racked right on top of each other. I do have the shallow wireless racks so the antennas are exposed.
I was wondering if anyone is using the omni remote antenna kits that Sennheiser makes. They only come in sets of four for the remote antennas but my racks are in sets of 10. It seems like that is the best configuration for our shows. Currently I am in a show that uses eight mics which gives me two backups. Plus as they continue to take frequencies away for wireless mic use, I wonder if the remote antennas would work as I upgrade my wireless system.
If anyone has any suggestions that would be great. Also if you have some pictures of your set up I would like to see them. I am always looking for good ideas and this forum usually has them.
Thanks,
Brent
 
If you are suddenly having RF issues that you didn't have before assuming your system has been static, it means there is a new source of RF interference in your area that you need to coordinate around. If you added stuff and you suddenly have issues, you are the cause of your issues. The first step in any RF system is to properly coordinate your wireless so you are sure that you are a. clear of outside interference from TV stations and neighbors using wireless and b. aren't stepping on yourself with intermodulation products.

As for antenna distribution, it is advisable to get some sort of antenna distribution with a system that large. I am spoiled in that I can call up any of the rental shops in NYC and get a 16 or 24 port antenna distribution system that has cascade outputs that allow me to get as large as I want (Check out PWS - Professional Wireless Systems). The sets of antennas you are referring to are intended to be used with some sort of distribution amplifier (ex. Sennheiser ASA-1, Senheisser ASA3000). As for antenna selection, I would go with the Sennheuser UHF-2003-A "Sharkfin" as it is more directional. Omni's are great as transmit antennas for things like RF Intercom, but you don't need to be picking up all the things behind and around you with your RF Rack is at FOH. If it's in your budget, pick up 2 ASA3000's and 2 UHF-2003-A's. Because your distribution probably won't have input attenuation, make sure you get the same length cables to go to both antennas to keep your RF Diversity intact (in moderate loss cable you will see around -2.5dBm attenuation per 25'), I commonly suggest RG-213 for antenna cable and RG58 for patch cable. Properly coordinate your wireless, and you should be good.
 
With the transmitters off and the receivers on, check the RF level of each receiver. You should be able to tell if there is some new RF noise source, and get an idea of the frequency it is at by seeing which receiver has the highest RF level on it then check the frequency preset on that receiver. A big culprit in the A band is some of the new LED lights out there. (Not theater fixtures, but direct replacement lamps used in regular fixtures.) Go back to the Sennheiser chart and select factory channels as far away from that frequency as you can cram them, or, if you have software, create your own chart. I ran into this last fall and it was so bad that I thought the mics were on! Still, I was able to thread the needle and everything worked out fine.
 
JD said:
With the transmitters off and the receivers on, check the RF level of each receiver. You should be able to tell if there is some new RF noise source, and get an idea of the frequency it is at by seeing which receiver has the highest RF level on it then check the frequency preset on that receiver. A big culprit in the A band is some of the new LED lights out there. (Not theater fixtures, but direct replacement lamps used in regular fixtures.) Go back to the Sennheiser chart and select factory channels as far away from that frequency as you can cram them, or, if you have software, create your own chart. I ran into this last fall and it was so bad that I thought the mics were on! Still, I was able to thread the needle and everything worked out fine.
Click to expand...

Nothing beats starting with a good coordination from an intermodulation computer program and proper antenna placements. As far as LED RF Interference goes, it isn't the LED's themselves but their switching power supplies that cause the interference look for lamps stamped with the FCC Part 47 stamp guaranteeing no EMI emissions. That being said, the interference put out from LED Lamps is commonly from 30mHz-300mHz -- so not in the ranges of UHF RF. Even their second order harmonics would most likely not have the power to cause issues.

Looking at RF levels on the front panel of the display is imprecise and messy. Selecting factory preset freqs is cool as long as you aren't near any TV transmitters (or know the TV stations in the area you want to avoid) and as long as you stay in the entire bank -- When you have 12 preset banks each with 12 freqs, they have guaranteed that each individual bank is intermod free, it is up to you to figure out which bank you can work in and you have to stay within the bank only. Trying to go "as far away" from a problem freq isn't really great advice, assuming intermod products don't exist and wouldn't be an issue and LED lamps actually spew RF interference that could junk up UHF RF you could probably tune up a half a megahertz from the problem freq and be just fine, it's such low power that it's probably narrow band interference. I have inserted photos below to show this, below the photo are freqs I coordinated plus the intermod products I am living next to just fine.
HLHelical520-530.png


You can see in this photo I have RF at 520.475, 522.250, 528.650, and 529.675. Knowing this, you can see how close I am to large points of interference (Intermod from the rest of my wireless) at 521.9, 529.9, 524, 524.25, 528, and an intermod product that dwarfs my regular RF at 528.250 (less than half a megahertz from the good freq I am using).

HLHelical580-590.png
This one just shows what a TV station does to wireless and why you can't beat a TV station.
 
Thank you for the responses. This is the first time that I have worked in this theater with wireless mics. I did do a scan of frequencies with the transmitters off. I took the squelch on the receiver that was scanning down to its lowest setting. With the transmitters off I was only getting a little RF on the receivers. It was very low. None of them would come of RF mute with the little signal it was picking up. Once the actor came out on stage and was standing still the signal would be solid. The minute they would start to move the RF would drop enough to create some static and some RF interference. The transmitters live under the actors clothes in a neoprene pouch with the antenna coming out of the pouch. There are some LED lights above the FOH position but the are not on during the performance.
I am curious about the spectrum software that you are using. Who makes this software? What is needed to use the software? Antennas?
My biggest question is should I spend the money on the antenna amplifiers. They are very expensive and I can start to slowly acquire one a year till I have enough to cover all the wireless mics I own (25). However by the time I have the antennas will I need to upgrade to a system that doesn't work with the antenna amps that I have purchased? Is digital the way to go? The 2.4 ghz range. Our school just upgraded their wifi system in the 2.4ghz band. Is the range for those any better than the analog system I have? Any responses would be greatly appreciated.
Thanks,
Brent
 
Bgarrett74 said:
I did do a scan of frequencies with the transmitters off. I took the squelch on the receiver that was scanning down to its lowest setting. With the transmitters off I was only getting a little RF on the receivers.
Click to expand...

Did you coordinate your wireless for intermod after you did a scan? You can do all the scans in the world, but unless you are making sure you aren't stepping on yourself you'll still have issues. Squelch won't usually be something you have to care about when you do a scan, though you will care about it when you are actually using RF in a noisy environment -- you can use Squelch like you would use a noise gate on your audio console. Don't use a lot of it and you'll open yourself up to low-level transients, use too much of it and your signal may not punch through at the outer edges of your range.


Bgarrett74 said:
I am curious about the spectrum software that you are using. Who makes this software? What is needed to use the software? Antennas?
Click to expand...

The particular software in the images was Touchstone Pro, I was testing it out a few months ago on a gig comparing it to a few other programs along with a variety of antenna combinations on a particularly troublesome gig. In that instance it was connected to an RF Explorer that was analyzing a PWS S8089L Helical LHCP through that RF systems Antenna Distro (Masque Sound 24 channel Attenuator/Splitter) so I could analyze exactly what my RF Receivers would be seeing. I took the data off the scans and imported it into PWS's Intermod Analysis System for my coordination.

Bgarrett74 said:
My biggest question is should I spend the money on the antenna amplifiers. They are very expensive and I can start to slowly acquire one a year till I have enough to cover all the wireless mics I own (25). However by the time I have the antennas will I need to upgrade to a system that doesn't work with the antenna amps that I have purchased?
Click to expand...

Buy wideband amplifier/splitters, you don't need to purchase into Sennheiser's system, there are other 3rd parties that offer plenty of options that cover the entire UHF spectrum. There is a marked improvement over using the 1/4 wave whips.

Bgarrett74 said:
Is digital the way to go? The 2.4 ghz range. Our school just upgraded their wifi system in the 2.4ghz band. Is the range for those any better than the analog system I have?
Click to expand...

There is a difference between digital wireless and 2.4gHz wireless. I would stay away from wireless in the 2.4gHz range, last time I tried them out (a few dozen units on a moderately large gig) it was mayhem fighting with multitude of building networks. The cost is good if you are running 1 or 2 units, but if you are running as many as you are, UHF is still the way to go. The expensive digital wireless on the market (Sennheiser 9000 Series, Shure Axient) are still using UHF transmission but with a digital signal instead of an analog signal -- it comes with performance benefits and better sound, but at a significant cost for the quality ($30k for 8 channels!).
 
themuzicman said:
The expensive digital wireless on the market (Sennheiser 9000 Series, Shure Axient) are still using UHF transmission but with a digital signal instead of an analog signal
Click to expand...

Last I checked, Axient was still using an analog FM carrier, just with the smarts of on the fly frequency changing and the like...
Am I remembering wrong?
 
Chris15 said:
Last I checked, Axient was still using an analog FM carrier, just with the smarts of on the fly frequency changing and the like...
Am I remembering wrong?
Click to expand...

Nope, you're right, my bad. I've only actually used the 9000 series, just pulled the top 2 expensive products and forgot the specs. Axient is traditional FM with a fun diversity scheme to frequency hop, analog transmission with computerized backend.
 
You should also check out a company called rf venue they make a few unique products that could be very useful and are cost effective as compared to some other products out there. We just own some of their stuff along with pws shure akg etc ... so I'm pretty familuar with all the gear.

There is a great article on rf venues blog about noise floor and how maybe a big Ole gain antenna may not be the best for your setup because if you gave interference it's just picking it up stronger. ..

My first thought would be the spotlight antenna and a helical ... place the spotlight as close to stage as possible with appropriate level of booster gain ...

Another product they have that I really like for theaters is the diversity fin directional amd omni reception ... +1 for the pws stuff it's awsome also.

You need antenna combines it will help your receptuon with that many channels.

Have you tried remoting receivers to "monitor world" think concert sidea stage ... and running mic lines back to foh??
 
brin831 said:
There is a great article on rf venues blog about noise floor and how maybe a big Ole gain antenna may not be the best for your setup because if you gave interference it's just picking it up stronger. ..

My first thought would be the spotlight antenna and a helical ... place the spotlight as close to stage as possible with appropriate level of booster gain ...

Another product they have that I really like for theaters is the diversity fin directional amd omni reception ... +1 for the pws stuff it's awsome also.
Click to expand...
A Spotlight and a Helical is an odd choice for an indoor theater, I would always start with a cardioid antenna like the UHF-2003-A and work my way to a tighter pattern depending on usage. Helicals are great outdoors when you don't have the room giving you RF reflections back to your antenna, but indoors they are usually rather useful on IEM's so you can point them and know you can keep the pattern tight. In an indoor venue, let the room help you, so you keep the pattern more open on the Rx antenna.

After extensive testing of the RF Spotlight, it's hard to recommend it for use as a main antenna for a large musical RF system, unless your stage is rather tiny. The Spotlight is a remarkable product, but in a very narrow band of applications, you lose about -10dBm of reception, which means your system is less prone to transient RF interference, but at the expense of RF operational range -- I found it to be an especially awesome tool to add to my RF toolbox in 3 distinct areas,

1. When you have a few speakers in a single area, and you want to make the RF rock solid.

2. When you need to add a 3rd antenna into your diversity system and the 3rd area is a trouble spot in a set (yes, uncommon, happens a lot in large-scale theatrical productions, I do at least 2 or 3 shows a year that require having a 3rd antenna on a traditional 2 antenna diversity system), you do this by padding the heck out of the antenna so you have no chance of comb filtering your diversity system with the tertiary antenna and using a combiner to add them to whichever antenna is the weaker of the 2 in the trouble spot.

3. When you need rock solid IEM coverage of a single person in a tough RF environment. You can get your antenna literally right on top of the person needing the IEM and you can keep transmit power super low this way.

You really need to find a way to build it into the show deck, you don't want to toss the spotlight center stage on a show and have people walking over the cable all show.
 
FWIW, I use the EW300's and the ASA-1 and 2 of the A2003 yagi (cardio) directionals spaced 1/4 wavelength apart (~5 inches) positioned out at the FOH booth. So far always solid RF path even in
dense areas of SOCAL. Of course sounds like you would need 4 or more of those so gets expensive quick. As someone mentioned above you can get a similar set up from other vendor. Other nice
thing is the ASA-1 powers 4 of the EW300's so only 1 power plug/wallwart per clock of 4. Maybe not a big deal if you already have them racked up and powered.
 
If the transmitters and receivers that far apart, the gain of a helical is what you want. (If you put your eye 12" behind the back plate of a Shure/PWS helical and look through the barrel, what you see is what you receive from. At 70', the coverage will be plenty wide.)
 
My 2 cents: I'm running 13 (lucky number) Sennheiser Ew100 G3's, and recently added an RF Venue Distro and Diversity Fin antenna to my rig. I have seen a HUGE improvement in signal quality, loss of drop out, etc. Originally I as using small antennae on the Sennheiser Antenna Distro's. The move to the Diversity Fin is like day and night for signal reception.
 
Thanks for the replies. I will put this info to good use.
Since I have racks of 10 receivers does anyone have a good way to combine all the power of the receivers to one DC to AC plug. I have a good idea but maybe someone out there has done this a better way. Since I have 10 receivers I don't want to have 10 wallwarts. It gets pretty messy. I know the antenna distros can do that but I don't currently have the money to buy them.
Thanks,
Brent
 
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