Wireless Radio Installation CH70 Issues

Robin9

My church has a wireless lapel/hand mic installation operating on CH70 - our mics are around 770 Mhz. We hold a PMSE license for these frequencies.The speakers are hardwired .Original installation 2013.

Since 2016 we have experienced brief bursts of "noise" - quite unpredictable.

I am aware of the withdrawal of CH70 by May 2020 and we are registered for the grant - we expect to do a complete replacement and then operate on CH38.

Could this issue be 4G related - we have two masts within 1/2 km. ?

Will the change to CH38 solve the problem.?

Norman_Castle

Could you tune a radio to the ch38 frequency to check for interference?

Robin9

Thank you for the suggestion - however to change from CH70 to CH38 means a complete change of transmitter and receiver which are made specific to the channel

Biggus_Dickus

Robin9 wrote: »

Thank you for the suggestion - however to change from CH70 to CH38 means a complete change of transmitter and receiver which are made specific to the channel

• (Ch.70) Directly below 863MHz there is 4G mobile phone data transmission, there is no buffer so it is possible that some users may experience interference at the lower end of Channel 70 (around 863MHz).

The alternative to shared spaces, deregulated or licenced, and generally considered the best option for churches is a ‘fixed site licence’, (aka ‘interleaved’ or ‘co-ordinated’ frequency Licence). These are individual radio frequencies specifically allocated to each radio system you have at your church location. They help ensure interference free operation. These frequencies will likely be dotted around the radio spectrum so it is advisable to obtain them first before purchasing radio mic equipment. However, as not all products will tune to all possible frequencies and research is required to find a clear frequency in your area we strongly recommend we administrate this process for you on a yearly basis.
• Around £40 per Licence (renewed yearly) including DM administration.
• Best option for interference free operation.
• Radio Mics can only be used at the church.
• Requires research to select a usable frequency in your area
• Requires Radio Mic Systems capable of tuning to the licenced frequency – see our Choosing the Right Radio Mic equipment guide.

https://www.dmmusic.com/radio-mic-frequencies-licensing/

Norman_Castle

Robin9 wrote: »

Thank you for the suggestion - however to change from CH70 to CH38 means a complete change of transmitter and receiver which are made specific to the channel

I might be misunderstanding the equipment you have but am assuming it is a low power transmitter transmitting on 770mhz which any AM radio should be able to tune in to. If this works at your current frequency can you then use the same method to check the ch38 frequency. The only equipment you would need is an AM radio.

thorganby

Nobody can tell you if moving from PMSE Channel 70 to the new PMSE allocation of Channel 38 will solve your noise burst problem because it basically depends on the ability of the new equipment to reject unwanted interference that may swamp your radio mike systems receiver.

Currently your radio mikes operating on Channel 70 (863-865 Mhz) are more likely to suffer irregular interference from 4G mobile handsets up link, rather than 4G base stations which transmit on higher frequencies than the mobiles up link.

There is no point trying a radio mike system operating on Channel 38 at the moment because only when the 700 Mhz band is cleared of current users, will it then be used to expand 4G mobile.

It is likely that the new PMSE equipment will be much better at rejecting unwanted signals than your current set up which was only required to reject low level signals from distant transmitters rather than locally generated higher powered transmissions from 4G mobile handsets e.g. mobile handsets often operate in close proximity i.e. in the same room using adjacent channels with no interference to each other.

Owain_Moneysaver

The people on the Blue Room forum are pretty knowledgeable about radio mics and licencing

https://www.blue-room.org.uk/index.php?showforum=3

virgo17

Norman_Castle wrote: »

I might be misunderstanding the equipment you have but am assuming it is a low power transmitter transmitting on 770mhz which any AM radio should be able to tune in to. If this works at your current frequency can you then use the same method to check the ch38 frequency. The only equipment you would need is an AM radio.

770Mhz is a UHF frequency will need a scanner or other more specialised receiving equipment. 770 Khz is a low frequency which could be received on a basic LW/MW domestic receiver.

This post relates to UHF frequencies which are co-existing between mobile phone networks and other (PA & Microphone) users, at present.

System

Norman_Castle wrote: »

I might be misunderstanding the equipment you have but am assuming it is a low power transmitter transmitting on 770mhz which any AM radio should be able to tune in to..

Not a chance in hell of an AM radio of the type you're thinking of tuning into that. You seem to be confusing Kilohertz with Megahertz.

thorganby wrote:

]Nobody can tell you if moving from PMSE Channel 70 to the new PMSE allocation of Channel 38 will solve your noise burst problem because it basically depends on the ability of the new equipment to reject unwanted interference that may swamp your radio mike systems receiver.

Yes they can, until I sold some of my gear I could, and I only do radio at a hobby level as a radio amateur.

To the OP, what you need to do is find someone with a spectrum analyser or a receiver that covers the frequencies intended to be used, you may find if you contact your local amateur radio club they have someone who can help. They then need to visit the location, fire up the analyser/receiver, see what is being received by that on the frequencies you're intending to move to. The one I used to have, which was a budget level Rigol 815, would allow me to listen to the signals it received.

Heedtheadvice

Interference from mobile phones (transmitters where you have no control over their use) and the like is a common problem for radio mics, hence reliable systems use those dedicated licensed frequencies mentioned in another post. These are generally well controlled to prevent interference.
System design can also alleviate or prevent the interference. Often the problem is worst in built up or industrial areas where there are more transmitters in the local area and where there is sub optimal signal between mic and receiver.



Does your receiver have an external antenna?
If so is it just a simple dipole (straight stick like)/stub type?
If so replacing with a directional antenna and moving closer to the mic transmitter might aleviate or even cure the problem.
The uhf antenna stub types are often omni directional and can be replaced by difectional types, wideband suitable for channel 38 and 70(and those between) etc. so probably can be reused when you move channels. Your receiver manufacturer may even sell one. They improve your signal reception and help reject the interfering signal(s) on a directional basis.

Cost often below £200.

Heedtheadvice

As an example only to give you an idea https://www.rock-tech.co.uk/cms/products/directional-active-uhf-antenna-470-870-mhz-all-uhf-channels-21-to-70?web-page-id=194
is a powered one but there are also passive ones requiring no power......and other suppliers and manufacturers!!!