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RF Question - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | 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 antenna.
(d) The improvement in S/N (for both cases (i) and (ii) above) which
would result from
- replacing the ribbon cable with a polyfoam cable, attenuation
0.04 dB/m
- 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 the same.

Anyone gives some hints for solving this question
thanks in advance.


Post subject:
Unread postPosted: Sat Apr 02, 2005 9:20 pm

Most tutors that help you with college homework problems get paid. What are you offering?


Post subject:
Unread postPosted: Sun Apr 03, 2005 3:02 am

Do I have to show my work?


Post subject:
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) + ...

Posted  11/12/2012

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