Re: [CAD_CAM_EDM_DRO] Re: Lost steps

Ian,
Heterodyne used to be the term used to describe the "whistle" produced when two adjacent signals where received in the old type TRF
(tune radio frequency aka "straight receivers") receivers, the signal got mixed and produced an audible tone, early morse code
receivers used a BFO (beat frequency oscillator), that deliberately made such a tone so that a simple CW (carrier wave) could be
used without modulation.
Super heterodyne is the term used was used to describe the process of mixing two signals and produce a difference signal that was in
the RF (radio frequency) and was NOT audible. this type of difference signal is normally called the IF intermediate frequency.
The whole point of developing a Super heterodyne was to make a receiver more selective and easier to tune, and therefore avoid the
whistle..
Gone are the days of 813's and 807's and thank goodness !
Hans W



Ian Wright wrote:

> ----- Original Message -----
> From: Mariss Freimanis <geckohall@...>
>
> > as superhetrodyne recievers when
>
> (super)hetrodyne - derived from 'heater' and 'dynamic' - in use they
> whistled like a boiling kettle.........? ;o)
>
> Ian