Frequency band usage

[bencordy]

So here goes my first post heard lots about the forum looking forward to contributing.

 

First I have a little question I'm stuck for an answer for. One of the venues I use fairly regularly has a pair of ew100g2 Sennheiser wireless receivers with associated mics (one belt pack one handheld). Presently they run on the frequencies 835.500 and 831.300. These haven't been adjusted for some time or so im led to believe. As far as I understand these frequencies aren't for free use or not anymore anyway. Is that correct? If so can the ew100 units operate in the free bands. Struggled to find a clear answer as to what those bands are.

 

Thanks for any help given!

[Speakercon]

They are on channel 66, but in band E. You should change them to channel 70 (863-865) so something like mic 1 - 863.100mhz & mic 2 864.300mhz. This is assuming you don't have any other UFH mics in channel 70 already & that there no are venues next door that are using them. Try it and find out with frequencies in channel 70 until you get something that works but there should be at least .5mhz in-between each mic.

[paulears]

Picking channels is not quite as simple as just keeping a fixed distance away -you have to consider intermodulation, so common 4 channel pairings in ch 70 are like these:

863.100 MHz

863.900 MHz

864.500 MHz

864.900 MHz

 

or

 

863.250 MHz

863.750 MHz

864.625 MHz

864.990 MHz

 

As you can see, the relationship between channels is not just a simple bit of maths - and even these frequencies may not work with all makes and even versions of similar products. When the band gets busy, you can also imagine what happens when somebody goes bang between these frequencies - as in 864.625 used in the same area may create problems for 864.9 and 865.5.

[mackerr]

Picking channels is not quite as simple as just keeping a fixed distance away -you have to consider intermodulation, so common 4 channel pairings in ch 70 are like these:

863.100 MHz

863.900 MHz

864.500 MHz

864.900 MHz

 

or

 

863.250 MHz

863.750 MHz

864.625 MHz

864.990 MHz

 

As you can see, the relationship between channels is not just a simple bit of maths - and even these frequencies may not work with all makes and even versions of similar products. When the band gets busy, you can also imagine what happens when somebody goes bang between these frequencies - as in 864.625 used in the same area may create problems for 864.9 and 865.5.

 

On the other hand, if the 2 mics the venue has are the only devices in that physical area, intermod is not an issue. You need 3 or more devices before you can suffer interference from intermodulation products generated by those devices.

 

Mac

[paulears]

I agree - my thoughts were that the likelihood of 3 or 4 is very likely at some point - so working on a compatible band plan seems sensible.