Free Air Capacitance?

Discussion in 'Royal Signals' started by EX_STAB, Jan 31, 2007.

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  1. Many years ago, a friend told me that the interference effect that you get when moving around a radio is due to altering the "free air capacitance". (This is what I remember)
    Recently, I've found that both radios in the house (one in a HI-Fi unit, one in a battery Roberts radio) sound fine when I stand next to them but are subject to a lot of white noise as I move away or around the room. This has become much more noticeable over a few weeks.

    What is the proper explanation for this effect and what can I do about it?
  2. Buy a new Hi-fi because yours sounds f**ked. Also get yourself a new anorak and get yourself down to the train station with all the other geeky gimps!
  3. A slight aside, and possibly irrelevant, but if you move any conducting material (aluminium, and water even, cf a body) then it will generate a small magnetic field - moving charge carriers and all that, relative to a stationary radio. The magnetic field has the potential to interact with the ambient electromagnetic field. The effect is tiny though, unless of course you're wearing a suit of armour and carrying a large stump of iron around with you.

    Do you like my tin foil hat? It's new.
  4. I'm sure I would remember if I'd had any metallic objects installed! Coins and pocket knife, belt buckle, wrist watch. Nothing's changed.
  5. propogation my dear boy propogation - radio waves travel at the speed of light - if it hits an object it reflects off it much like light in a mirror - your body is made up of 80% water therefore a good conductor hence when you touch an antennae your acting as a bigger one and generally get better reception - if your near it there is an effect much like placing a metal object into a magnetic field ie the magnetic field generally becomes stronger hence the reception becomes better or in some cases worse depending on the receiver sensitivity. Bottom line is best reception is direct line of sight if it uses FM so place antennae at suitable location or invest in an internet radio.
  6. Cheers for that. Makes sense now!