[cma-l] DAB trials

[Two Lochs Radio]

Yes, the multiplex signal itself is one size fits all. The 'couple of stations' does refer to economic factors rather than technical. For 10 stations each with a budget of (say) £1m sharing a 10kW transmitter the cost equation is a bit different from from a couple of stations each with, say, £30,000 budget buying a 100W transmitter.

The old first-principles way of measuring the average rms power of any arbitrary signal is to feed it into a resistive load and measure how much heat it generates. But more usually nowadays, spectrum analyzers, which are needed anyway for commissioning a broadcast transmitter, can easily measure the total rms power of a signal at an instant or averaged over time. Often there is an add-on pack for spectrum analyzers that contains extra bits (such as a directional coupler/SWR bridge and extra software) that calculates the various radio-related parameters such as power, spectral occupancy, out-of-band harmonics etc. 

And for all I know the digital signal processors in the SDR can also calculate  the average total power at the same time as they are doing all the amazing on the fly maths to create the signal in the first place - just a little bit more arithmetic for them to do on the side!

Alex

  ----- Original Message ----- 
  From: Tony Bailey 
  To: tlr at gairloch.co.uk 
  Sent: Tuesday, March 10, 2015 3:45 PM
  Subject: Re: [cma-l] DAB trials


  Thanks,

  Arising from that (without boring the readers!) I was under the impression that the mpex carrier was one lump, i. e. independent of the number of programme feeds, so presumably the "couple of stations" is an economic rather than technical factor?  How do you arrive at an average power figure for 1500 parallel carriers any of which could presumably be zero or 100%?  

  Tony
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.commedia.org.uk/pipermail/cma-l/attachments/20150310/82e2b4e8/attachment.html>