Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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My Hobby Website:
question of design - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: question of design Posted: Tue
May 02, 2006 2:45 pm
Joined: Tue May 02, 2006
how can we design a automatic gain control circuit
Post subject: AGC amplifierPosted:
Tue May 02, 2006 6:26 pm
Joined: Wed Feb
22, 2006 3:51 pm
You need two things for an
1. A way to measure the signal strength, and
A way to vary the gain based on that measurement.
come in two varieties, feedback (closed-loop, more common) and feedforward
(open-loop, less common).
Signal strength measurement is often
done by rectification followed by low-pass filtering.
two major ways to vary amplifier gains:
1. Varying the operating
parameters of a BJT or FET
2. Using a FET or a PIN diode as a controllable
Within those two major ways are a large number of specific
approaches, depending on frequency, dynamic range, etc.