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    Assigning a frequency already in use
    Topic posted July 31, 2012 by monty412Competent 
    108 Views, 3 Comments
    Assigning a frequency already in use
    So I've run into this issue on multiple occasions. When I turn on my rack in a new city and find interference on some frequencies, I'll let the Spectrum Manager give it a new one. Sometimes it will deploy a frequency that is currently being used by another receiver, causing an error on the second receiver and requiring that one to get a new frequency also. Shouldn't the Spectrum Manager know not to give out a used frequency?



    • Nick Wood
      Yes, the Spectrum Manager should only deploy a frequency to one channel, it should never 'double book' them. One thing to check is just to make sure the Spectrum Manager is definitely set up to control all the receivers in question. The easiest way to do this is probably from the front panel menu of the SM, in Manual>Devices. That will get you a list of all the Device ID's that the Spectrum Manager thinks it is controlling. You can Flash any one of them to identify the receiver with its LEDs.
      Another way to check is from the Receiver which was already on a frequency deployed by the Spectrum Manager. At the bottom of the Radio menu it will tell you the Spectrum Manager serving it frequencies (if any).

      If a receiver somehow was removed or did not get added to the Spectrum Manager's control during setup, that might explain why the frequency was considered available. It would also have to have been a clear frequency at the time.

      I hope this helps, please let me know if that wasn't the issue.
    • monty412
      Thanks Nick, I'm pretty sure that all the receivers are talking with the SM for their frequencies. The only times it happens is when turn on the rack, switch the channels that have interference and then when I fire up all the transmitters I see that there is a conflict.
    • Nick Wood
      Sorry for the delay getting back to you.
      If this is primarily happening when transmitters are getting powered on then it may be that the receivers are on the new frequency list but the transmitters are still on their old frequencies for a moment while they are coming online.
      The ShowLink association when the transmitter is first powered up can take a few seconds, at which point it immediately goes to the frequency of its linked receiver but during this time there could be conflicts or imd if you are doing a new coordination for every show. This may or not be an explanation depending on how fast the transmitters are getting powered on, but if so here are some suggestions:
      - power up transmitters into RF Mute state. The trick for this is to power on while simultaneously holding the 'set' and down buttons. Granted this is a little tricky, especially on the handheld, but the transmitters also remember this state if you power them down after RF Muting them through easier methods. When the transmitters come back on they will get their new frequencies and you can re-enable the carriers whenever needed from the regular transmitter menu, or the receiver front panel or Workbench.
      - staggered power on of transmitters. If the Access Point is set up and they are already linked from previous usage, this shouldn't require more than 6 seconds or so to let the transmitters settle on the new frequencies. That may reduce the amount of potential interference at one time
      - Leave receivers in Prompt or Detect Only Interference detection mode during the transmitter power up. The red backlight of the LCD indicates the actual presence of an interference condition, after which the alert stays up in Prompt mode but gives you a timer indicating how long ago it happened. After a few seconds the red backlights should go away and you can clear the prompts when convenient. If the receivers are set to Detect only you won't need to hit Ignore either since there is no Prompt, but you will then need to change the mode back if you want Interference Avoidance.

      You could also leave the receivers on their old frequencies while transmitters are coming on, but this probably depends on what else is going on at the moment.


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