Sennheiser XSW Radio Mics

[noise]

Hi all

 

Does anybody have any experience with these units? I seem to be struggling to set frequencies for 8 units on "Bank 1" (which has 12 available frequency presets). The presets either already have RF or AF interference. When I set them to tune automatically they struggled to find enough free frequencies each, even after scrolling through the 8 different banks. Bank 1 is Channel 38, so unfortunately I don't have a license to use any of the other banks. The units are the "GB" version with frequency range 606...630MHz.

 

I was under the impression it would be fine to use 8 units on Bank 1...

 

Any advice much appreciated.

 

Cheers

 

John

[cedd]

Are your transmitters on at this point? If not then I suspect the problem you have is nothing to do with the limitations of the equipment and everything to do with an interference problem.

 

If your transmitters are on then are they already tuned to your receiver frequencies or have you not got that far? Remember that even with the best equipment, a large number of transmitters very close to your receivers or aerials will cause some unpleasant results - the filtering just can't cope with it. Go a distance away from the receivers with your transmitters set to the correct frequencies and see how they behave then.

 

Are you using an aerial distribution system?

[PatrickSmith]

Are you metering RF interference even when all the transmitters are turned off?

 

You should be able to get 8 into channel 38 in a clean RF environment, but if there is a lot of other RF use in your vicinity all bets are off as to how many you will succeed with.

[noise]

Hi Cedd

 

Thanks for your advice. I've just been turning them on one at a time but yes, have been close to the receivers, however receivers have been switched on. I'll turn off all receivers and transmitters and then turn them on one at a time but will keep the transmitter at a distance. Not using an aerial distribution system, Will let you know how I get on - thanks!

 

Thanks Patrick - I'll only see RF interference on say the fourth unit, after I've already set the first 3.... Will give it another go!

[cedd]

Ok, let me suggest a fault finding order;

 

Turn off all transmitters, turn on all receivers, set all receivers to the frequencies you plan on using them on. Are you seeing any RF metering on the receivers? If so, how many of them?

 

If you are seeing stray RF on some of the receivers, try tuning one of the unaffected receivers to that frequency - does it now show the stray RF also? If so then you look to have an interference problem. Not sure if it's an option on the XSW's, but at this point it might be a good idea to switch off the pilot tone on the receiver, turn down the squelch and see if you can hear anything recognizable in the RF.

 

 

If all of the above tests out ok then it's time to start switching on transmitters. Switch each transmitter on individually, check that only its' corresponding receiver shows RF, then switch off again. Do this for each transmitter.

Then switch on all transmitters and take a look at the receivers - are they misbehaving? If so then turn off the corresponding transmitter and see what the RF display on the receiver does - if it meters something then it's most likely an intermod of 2 of your transmitters that are still switched on - try a different frequency.

 

It's very tricky to do RF fault finding by remote control, but if you carry out the above and let us know the results then it gives us a fighting chance of working out what's going on.

[noise]

Thanks so much Cedd - will follow above and let you know how I get on :-)

[paulears]

Bank 1 should be fine - using the free tuning feature is not a good idea with multi channel systems because you're looking for empty space, but not empty space that is intermod free. It's handy when you want to find just a single channel in the middle of loads of weaker, but troublesome frequencies. All the transmitters have output at low level on lots of other channels - it's not normally a problem, but doing a free frequency search with lots of transmitters locally will generate some weird results. The preset channels in Bank 1 are in the right band, and you should be able to pretty well use any of them to make up your 8 with no intermod issues. I think I'd start by selecting the 8 on the receivers, then seeing on the displays if any are already occupied. If they're free - then turn on the transmitters and all ought to be well. With Sennheiser kit I've always looked at the different models as they go up in price as almost identical audio quality, but gradually improving RF design and performance - so filtering and bandwidth improve. The lower priced kit can suffer from problems with local strong RF sources near the operational frequency, and the kit costing much more deals with it better. That said - unless you really are in an RF trouble zone, your needs are within the capabilities of the system.

[ramdram]

Ref Paul's last sentence, where are you trying to set up the kt?

 

If it is inside a granite walled structure eg. a medieval church then that adds yet another dimension to what is displayed on the rf "meter". I have had satisfactory readings of rf reception, which can vanish should the tx get near to a granite column.

 

However, what might be perplexing is that the AF will still sound almost reasonable even when there is no apparent rf signal on the meter/leds.

 

Might pay you to set up the kit away from said structure then, when back inside the structure, experiment to find the optimum(?) position for the rx aerial(s), and, be sure to have long enough leads (balanced) from rx to desk. (If you had a single aerial through an rf distribution amp then you have only the one aerial to worry about.)

 

 

You would be wise to have someone wondering about in the "acting space" wearing the tx pack and nattering away for satis audio while you move the rx around.

 

You could google up "multipath reception" if arsed. If nothing else it might help you get to grips with using rms in "iffy" spaces.

[noise]

Hi guys. Think the problem was having the transmitters and receivers all too close together. Tuned the units one at a time and moved them a few feet away from the receivers each time I'd tuned one. All working perfectly one Bank 1 :-) Thank you!