"Tom Holden" wrote in message
.. .
Jan-Martin Noeding, LA8AK wrote:
Mentioning a certain voltage level doesn't really make so
much sense when you don't know what the rest of detector
stages looks like. [snip]

Thanks for the interesting examples, Jan-Martin. The quote was from the
2004
ARRL HB page 17.23 in reference to a schematic/block diagram of a "typical
superhet receiver with AGC applied to multiple stages of RF and IF". The
RS
DX-394 bears some resemblance to this with a resistor in place of the
"Delay
Diode". It beats me how the AGC in this HB example actually controls the
RF
gain - the diode appears to block control. A second one in parallel in the
opposite direction seems to me to be needed.

Tom


Tom,

I don't have the circuit, but have two diodes pointing down. Resistors
on both anodes to +V. Common cathodes with resistor to GND.

+V
___|______
| |
R1 R2
a_| |_b
| |
V V
- D1 - D2
| |
| |
__________
|
R3
|
|
GND

Changing the voltage at point "b" will cause "a" to also change. Another
way to look at it is that you steal different amounts of current away from
D1. Go too low at "b" and "a" won't change any more. It stops. However,
go higher on "b" and "a" keeps going up. It is a limiter.

--
Steve N, K,9;d, c. i My email has no u's.