Sennhesier Evolution ADU Problems

[slim_mcslim]

We are currently having problems with a 4 way evolution rack. It comprises 4 x Evo 100 G2 recievers and 1 x ADU mounted in a 3u flightcase, with the outputs wired to a plate on the back. It seems that at any one time 2 of the recievers don't work properly, they all work 100% signal when the transmitters (usually bodypack) are within 10m of the receivers, however if you move much further away 2 of the recievers drop to half, sometimes its the bottom 2 receivers, sometimes its the top two. This rack pretty much always gets used with the same four body pack transmitters.

 

When the signal drops to half the audio quality going into the desk starts getting hissy and eventually drops out mid sentence.

 

Has anyone else had a similar kind of problem?

 

I am guessing that the ADU has had it, but I thought I would ask here first before swapping it out to one from another rack.

 

 

Paul....

[Peter Chivers]

I've had a similar problem with my Sennheiser Evolution radio mikes. According to the bench engineer that does our repairs, it is a fault on the receiver RF board, and is common to both G1 and G2 versions of the radio mikes.

Sorry to be the bearer of bad news as the boards are not cheap :) .

 

Peter

[StevieR]

A couple of other quick things to check before looking for faults...

 

1. Are you using AB2 antenna booster amps with the splitter? These will help make up for the losses introduced by the split. Also, make sure you use low-loss cable to connect the Antennas.

 

2. Are the 'Squelch' settings on the receivers a bit on the high side. If you are getting poor RF response, dropping the squelch threshold will keep the audio channel open longer before going into mute.

[cedd]

Have you used the supplied cable or your own?

 

Just have a quick check to make sure it's 50ohm loaded cable before you look at the expensive stuff.

[David]

Hi SLim

Hav sent a PM

 

David

[slim_mcslim]

As a further update, all the internal links in the rack are 50R cable and connectors, the links from the rack to external antenna are done on VDC pre made 50R cables.

 

I have used the antenna boosters, with the paddle aerials, standard aerials, and tried both without the unit and always seem to get the same level of dropoff. As a further update, I have stripped the units out of a rack and have them on a show with me now back on the individual power supplies and a forest of antenna's and they seem to be fine, all the RF is rock steady. So can only conclude that the orginal ADU must be kerputt

 

P.

[David]

Hi Slim

 

Thers nothing in the ADU to go kerputt. Its a power supply and a passive splitter.

 

David

[StevieR]

...all the internal links in the rack are 50R cable and connectors, the links from the rack to external antenna are done on VDC pre made 50R cables.

 

What is the type of cable for the antenna feeds - RG58, RG8X, URM67? And what length are they?

[Bobbsy]

Some parts of you description, particularly the fact that it's not always the same receivers that drop off, suggests to me that this may be a problem with your frequency plan. You may be getting intermod interference between the frequencies you have chosen which becomes more of an issue as the transmitters get farther away from the receivers.

 

If you want a quick and dirty check to see if we're on the right track, move the transmit packs to a "problem distance" and switch them on one at a time. If turning on another TX pack suddenly makes a receiver that was previously working properly drop in signal, then you likely have frequency problems.

 

A more scientific way to work out if your frequencies are compatible is to download the Sennheiser SIFM programme from HERE on their site and enter the required details. This should give you a prediction about any problems you might get with your frequencies or, used in another mode, suggest a working frequency plan for you. Obviously you have to be aware of what frequencies are legal to use with your licence (or unlicenced if you work that way). You don't mention anything about what frequencies you're using, but if you're trying to squeeze 4 EVO100 systems into the unlicenced band this is probably the problem.

 

Bob

[mackerr]

We are currently having problems with a 4 way evolution rack. It comprises 4 x Evo 100 G2 recievers and 1 x ADU mounted in a 3u flightcase,

When you say ADU I assume you mean antenna distribution unit, do you know the model number? Do you know if it is for the RF band your mics are in?

 

It is rarely a good idea to put an RF booster on wireless mic antennas. It is much more likely to cause issues with overdriven RF inputs to the receiver than to solve reception problems. A booster should only be used where the line loss in long antenna cables is a problem. Directional antennas should be used to help eliminate unwanted RF from the system.

 

If you are using RG58 for your antenna cable, you might be better off with 75 ohm RG59. The loss in RG58 is quite high at UHF frequencies, and since the actual source and load impedances of wireless mic anteanns and receivers is rarely 50 ohms, but rather somewhere between 50 and 90 ohms the slight impedance mismatch is unlikely to be any worse than 50 ohm. The best choice for wireless mic antenna cable is usually a double shielded low loss cable like LMR400 or RG213.

 

Mac