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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RF question - 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: RF question
Unread postPosted: Sat Apr 02,
2005 12:42 pm
A television receiver tuned to a channel at 220
MHz comprises a front end
amplifier (G = 18 dB, F = 2.5 dB), mixer
(G = 16 dB, F = 12 dB) and IF
amplifier (F = 2 dB, Bn = 6 MHz). It
is connected to an antenna of gain 6 dB
via 15m of 300 ohm ribbon
lead with an attenuation of 0.12 dB/m. Calculate
(a) The noise figure
of the receiver.
(b) The signal (in mV) at the antenna terminals
required to produce an
output signal to noise ratio of 40 dB for
(i) a suburban area, (i) a
quiet semi-rural area.
(c) The corresponding
electric field strength in the neighbourhood of
The improvement in S/N (for both cases (i) and (ii) above) which
would result from
- replacing the ribbon cable with a polyfoam cable,
- leaving the cable the same, but fitting
another antenna with a
gain of 10 dB
- leaving the cable and antenna
as originally and fitting a masthead
amplifier with F = 2 dB and
G = 20 dB.
Assume in each case that the signal field strength is
Anyone gives some hints for solving this question
thanks in advance.
Unread postPosted: Sat Apr 02, 2005 9:20 pm
Most tutors that
help you with college homework problems get paid. What are you offering?
Sun Apr 03, 2005 3:02 am
Do I have to show my work?
Unread postPosted: Wed
May 18, 2005 10:07 pm
Start with the cascaded Noise Factor calculation...
Ftotal = 1 + F1 + F2/G1 + F3/(G1*G2) + F4/(G1*G2*G3) + ...