12 Jul
2007
12 Jul
'07
9:30 a.m.
dwight elvey wrote:
Brent Hilpert wrote:
From: Allison <ajp166 at bellatlantic.net>
Hi
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
super-regenerative.
Dwight 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.
(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.)