Interference
Interference occurs when a transmission on one Network channel degrades or prevents the use of another. Because every allocation within the Velocity Interoperability Network is recorded in the Register of Allocations, the Communications Department of the Velocity Interoperability Network can in most cases identify the source of interference from the register and direct the changes needed to resolve it. This page sets out how interference is classified, how to give notice of it and what is expected of holders.
The Department's authority extends to every allocation and licence recorded in the register. It may vary an allocation, attach conditions to it or suspend it in order to resolve interference, and its directions take effect at the time stated in them. The Department does not adjudicate between holders; its concern is that the channels of the Network remain usable for the purposes for which they were allocated.
Categories of interference. Every notice is assigned to one of four categories on acknowledgement. The category determines the time within which the Department acts and the remedy it is likely to direct.
| Category | Description | Response | Usual remedy |
|---|---|---|---|
| 1 | Harmful interference to a Class A or Class D channel | Acknowledged within one hour; source directed to cease within four hours | Immediate variation or suspension of the interfering allocation |
| 2 | Harmful interference to a Class B or Class C channel | Acknowledged within one working day; resolved within five working days | Variation of one or both allocations |
| 3 | Degradation of a channel that remains usable | Acknowledged within one working day; resolved within twenty working days | Change of channel, power or antenna direction |
| 4 | Occasional or intermittent nuisance | Acknowledged within five working days; reviewed at the next renewal | Recorded against the allocation; conditions may be attached at renewal |
Interference with a Class A channel threatens the routing, timing and authentication of the Network itself, and interference with a Class D channel prevents official announcements and emergency notices from reaching members. Both are treated as Category 1 whatever the severity, and the Department may direct the interfering equipment to cease transmitting before its investigation is complete.
Giving notice of interference. The steps below apply to every notice. A notice that omits the information in the first step will be acknowledged but cannot be classified until it is supplied.
Step 1: Record what you observe
Note the channel affected, the date and time at which the interference began and ended, whether it recurs, and the effect on your service. Where your equipment records signal measurements, retain them.
Step 2: Check your own equipment
Confirm that the interference is not caused by a fault in your own installation or by equipment you operate on an adjacent channel. The Department will ask for this confirmation.
Step 3: Notify the Department
Send the record to the Department by email, stating the allocation you hold and the channel affected. A notice may be given by any member or by the operator of a shared service; a notice concerning a Class A or Class D channel may be given by anyone.
Step 4: Acknowledgement and classification
The Department acknowledges the notice, records it in the Register of Allocations and assigns a category. The category determines the time within which the Department acts.
Step 5: Identification of the source
The Department identifies the source from the register, first among allocations on the same or adjacent channels and then among licensed equipment in the area. Where the register does not identify the source, the Department may direct holders in the area to suspend transmission in turn.
Step 6: Direction and resolution
The Department directs the changes needed to resolve the interference. A direction may require a change of channel, power, antenna or operating hours, and may vary or suspend an allocation. The holder who gave notice is asked to confirm that the interference has ceased.
Step 7: Record of the outcome
The outcome is recorded in the register against both allocations. Where an allocation has been varied, the holder receives a revised allocation stating the new terms.
Notices are sent to contact@communications.gov.vin. Where interference with a Class A or Class D channel is observed outside working hours, the notice should be marked as urgent in its subject line; the Department monitors these channels continuously and will act on the notice when it is received.
Obligations of holders. The following obligations attach to every allocation and licence and are conditions of holding it.
- Operate within the allocation
- Transmit only on the channel, at the power and from the location recorded in the Register of Allocations. Any change requires a variation of the allocation before it takes effect.
- Maintain equipment
- Keep transmitting equipment within the limits of its certification. Equipment that drifts off channel or radiates outside its assigned width is the most common source of interference within the Network.
- Comply with directions
- A direction of the Department to change channel, reduce power or cease transmitting takes effect at the time stated in it. Failure to comply is grounds for suspension of the allocation.
- Give notice of interference
- A holder who becomes aware that its equipment is interfering with another channel, or that its own channel is being interfered with, gives notice to the Department without delay.
- Keep records
- Retain records of transmissions, faults and measurements for twelve months so that the source of interference can be established after the event.
Common questions.
The entry recorded against your allocation, including any notices of interference given or received, may be inspected on request. The bands and channels of the Network are set out under Spectrum Allocations, and the procedure for varying or renewing an allocation under Licensing. Further questions are answered in the frequently asked questions.