[cma-l] AM v FM

[Two Lochs Radio]

Appreciated, though there must be some comfort in the fact that the design has been 'standard issue' for a century, and is used by many of the most powerful AM transmitters such as Drotiwich. You might also find BS1386 of some interest.

The most critical aspects seem to be as you'd expect getting a good earth place below the capacity hat, and getting a high quality tuning coil with very low resistance and able to handle the relatively high voltages involved (but for a transmitter of a 100W or so that's not so tough). 

The client needs 'expectations management', I guess. If you find the theoretical antenna design would in all likliehood cut the client's electricity bill to a quarter, he might be willing to accept a little uncertainty in the exact radiation performance! If you could take the antenna efficiency up from 8% to say 30-40%, there's a very big saving in runnings costs to be had.

Alex


  ----- Original Message ----- 
  From: Ian Hickling 
  To: The Community Media Association Discussion List 
  Sent: Sunday, December 20, 2015 1:24 PM
  Subject: [cma-l] AM v FM


  I appreciate all the advice and input - thank you.
  I have the huge advantage of having worked in an engineering laboratory that built VHF and UHF antennas and range-tested them so I am very fortunate to have an inbuilt comprehension of how they look and perform.
  Nowhere in all that worthy information is there evidence of energy propagation patterns - actually measured in the field as opposed to calculated or computer modelled.
  Most important - the difference between success and failure.
  I can't guarantee to a Client how well an AM (MF) antenna will perform as I can with FM (VHF) - and that worries me.


  Ian Hickling

  Partner


  Office: 01635 578435  (7am-11pm UK time)
  Carphone: 07530 980115 (only responds when driving)
  6 Horn Street, Compton, NEWBURY, RG20 6QS
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