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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Noise figure Q - 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: Noise figure Q.
Unread postPosted: Thu May
13, 2004 6:55 pm
If a filter has 1dB IL at ambient, the noise
figure is 1dB. If at hot temperature, the filter has 1.5dB IL, will
the NF be higher than 1.5dB?
subject: Noise Figure will remain 1.5
Unread postPosted: Fri May
14, 2004 6:57 am
At higher temperature the overall noise power
floor will be higher (KTB). However, noise figure is the ratio between
the signal to noise ratio at the output to the signal to noise ratio
at the input therefore the noise floor is cancelled out and what is
left is the additive noise from the filter, or what you know as noise
figure. In this case the additive noise is 1.5dB, which is the noise
Post subject: Correction
to the formula
Unread postPosted: Fri May 14, 2004 10:48 am
Correction to the ratio you provided, the noise figure is the ratio
between the S/N in the input to the one in the output.
Unread postPosted: Tue May 18, 2004 11:38 am
NF is tested over temprature, is the ENR source in the chamber? Most
people have it out side the chamber and NF is calculated based on an
ambient reference temp.