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
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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: Best solution for RF protection Posted: Sun Jan
11, 2009 10:13 pm
Joined: Fri Jan 26, 2007
I've got a specification that allows as much
as +20 dBm into a receive input but many LNAs can't take that much power
without ruining the amplifier. Is there some kind of diode circuit that
can be used for protection against such a RF input without creating
distortion at a reasonably lower level? My input is relatively low frequency
Post subject: Posted: Fri Jan 23, 2009 3:18 am
Joined: Fri Jan 26, 2007 2:40 am
Post subject: Posted: Fri Jan 23, 2009 12:47 pm
Joined: Fri Feb 17, 2006 12:07 pm
There are one or two bits of data missing before I can
get my addled head around this one.
Is the frequency of the +20dBm
signal very close to weaker signals you are trying to detect/decode?
And is it at a fixed frequency or anywhere in the range?
+20dBm signal pulsed or continuous?
Are the weaker signals spread
over a random spectrum from 1-30MHz?
I would certainly look around
for bomb-proof front-end amplifiers, such as the approach using transmit
transistors with a measured and adequately low noise factor as the first
stage. This approach has been shown to yield very high IP3 figures.
At bottom, life is all about
and blowing out.
Post subject: Posted:
Mon Jan 26, 2009 5:58 pm
Joined: Fri Jan
26, 2007 2:40 am
The frequency is anywhere in the 1-30
MHz range. This is NOT a performance spec so much as it is a "damage"
spec. Another words we don't have to receive anything in particular
while this is going on.
I think the damage spec is "continuous".
The one thing that is tough here is that most gain block amps
I see have absolute max inputs no more than +18 dBm (most MiniCircuits
amps have +13 dBm). It's hard enough just finding an amp that will work
in this range anymore (due to most focus on the higher ranges) let alone
an absolute max this high. Therefore some sort of circuitry is needed.