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29937Re: [midatlanticretro] Re: Altair / Fool on the Hill question

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  • Dave McGuire
    Mar 29, 2013
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      On 03/29/2013 11:46 AM, joshbensadon wrote:
      >>> right inside the Altair. Start the demo by lifting the lid of
      >>> the
      >
      >
      >> Also, remember distance is your friend. unless there are
      >> directional antennas involved, signal strength is inversely
      >> proportional to the square of the distance.
      >
      > Yes, I had that in mind too when I suggested putting the radio right
      > inside the Altair box! Part of the demo is to show how it was done
      > wirelessly, but given the circumstances, it might need to go inside
      > the box. Also, he will need to watch that an open Altair box doesn't
      > interfere with his neighbor's demo.
      >
      > But, things might just work outside of the box, if the radio is
      > placed at the right position/angle.
      >
      > I wish I had more experience with the Altair Radio Music. But I know
      > the AM Radio antenna is based on a ferret stick,

      Ferrite

      > which should be directional.

      Ferrite "loopstick" antennas are very broadly directional. They have
      nulls off the ends but they're not terribly deep.

      > But, I think the interference really happens at the IF
      > stage, which is further down the receiver circuitry. If that is
      > true, you could remove the ferret stick antenna.

      Actually I'd be kinda surprised if the interference in question
      happened at IF. Those IFs are typically 455KHz; you're much more likely
      to get interference from higher frequencies than that in ~1~8MHz
      microprocessor circuitry.

      I've done it with a PDP-8; that interference comes from the
      high-current pulses in the core memory subsystem if memory serves. The
      interference there isn't at IF.

      > I'm sure the demo will sound good enough to get the point across. I
      > just like the idea of opening the Altair Lid to show off the
      > internals.

      I think it'll be great!

      -Dave

      --
      Dave McGuire, AK4HZ
      New Kensington, PA
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