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Moving in to Channel 38
Channel 38 is the frequency range 606-614 MHz and is currently shared with Radio Astronomy. Use of channel 38 requires a UK Wireless Microphone Licence which permits access for low power wireless microphones and monitors. Other applications including high power audio links will need be to be licensed in alternative spectrum.
Radio Astronomy will vacate channel 38 by 21 September 2011 resulting in channel 38 being available virtually UK-wide. Channel 38 will be fully available once Digital Switchover (DSO) is complete in 2012, but until then Ofcom has provided temporary access to channels 39 or 40 in the areas where channel 38 is not fully available. The licence does not specify spot frequencies, instead licensees are required to use our ‘Ch38 Look-up tool’ to check exactly which frequency ranges can be used at their location prior to operation.
After DSO is
complete in 2012 the whole range 606·5 to 613·5MHz will
be available UK-wide.
Guard bands have been included at each end of channel 38 to avoid interference with future services in channel 37 and channel 39 and facilitate free-roaming use throughout the UK .
10 Channel plan
The UK Wireless Microphone Licence does not specify spot frequencies in channel 38 but the 10 channel plan below will ensure that all frequencies can operate in the same location without harmful interaction. This plan is a suggestion only. Users and manufacturers can devise their own plans that could involve any number of frequencies within the range.
| Channel 38 - 10 channel set ratings | |||||
|---|---|---|---|---|---|
| 2Tx IM(3) and 3Tx IM(3) | |||||
| 25k0 | 50k0 | 100k0 | Risk Index | ||
| 606.600 | 0 | 2 | 2 | 
1.50 |
|
| 607.500 | 0 | 3 | 5 |
2.75 |
|
| 608.150 | 0 | 4 | 2 |
2.50 |
|
| 609.150 | 0 | 3 | 4 |
2.50 |
|
| 609.950 | 0 | 3 | 6 |
3.00 |
|
| 610.550 | 0 | 4 | 4 |
3.00 |
|
| 611.250 | 0 | 2 | 4 |
2.00 |
|
| 612.300 | 0 | 4 | 3 |
2.75 |
|
| 613.150 | 0 | 3 | 1 |
1.75 |
|
| 613.500 | 0 | 0 | 2 |
0.50 |
|
| Score total | 22.25 | ||||
| Average |
2.225 |
||||
In developing the plan we ensured that each frequency is safely spaced apart. However interaction can sometimes occur between frequencies even when appropriate spacing is applied. This unwanted interference can occur when equipment is operated close together in the same vicinity. It is known as intermodulation or “mixing”.
In the real world these unwanted signals appear on or close to the frequencies being used. To help make sense of this we have devised a figure of merit that we have called the “Risk Index”. This is calculated according to the quantity of unwanted signals and their spacing from the frequencies we are trying to use. Closer spacings have a higher risk of causing interference so are given a higher weighting in the sum.
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Channel 38 look-up
Look-up which frequency range is available in your location.