TTL homebrew CPUs - OT radio
hilpert at cs.ubc.ca
Thu Jul 12 11:30:24 CDT 2007
dwight elvey wrote:
> >From: Allison <ajp166 at bellatlantic.net>
> > >Subject: Re: TTL homebrew CPUs - OT radio
> > > From: woodelf <bfranchuk at jetnet.ab.ca>
> > >Well I found this surfing last night. Fet + Pnp = Strange radio.
> > >http://www.schmarder.com/radios/solidstate/homodyne.htm
> > >
> >That is a simple DC coupled amp that is used to first amplify RF then
> >the detected audio is passed through again. The fet is for high input
> >impedence and the transistor is for increased gain. Other wise know as
> >a reflex receiver.
> No, it looks a little like that but it is not a reflex. It is a homodyne.
> It uses feed back to cause oscillation of the first stage that zero
> beats the incoming RF. This makes the reciever very selective.
> The signal isn't rectified until it goes to the audio stage.
> The two circuits are similar. I've seen the combination of homodyne
> and reflex as well. These are usually just called reflex.
> Another similar method of getting selectivity is to make a
Brent Hilpert wrote:
> (And is actually a circuit dating from the 20's or earlier when designers were
> trying to maximise the benefit from each vacuum tube. Common as a one-tube radio
> design.) (Oh-oh, going OT).
Not wishing to drag this OT topic out, but in light of Dwight's point and for the
sake of accuracy I should note that my comment was restricted to Allison's mention
of the reflex circuit. (I hadn't actually looked at the link.) (Having done so,
it can't be a reflex as there is no feedback post-detection.)
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