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RF Problem - RF Cafe Forums
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MVALFRE
Post subject: RF Problem Posted: Mon Aug 01, 2005 5:51 pm
Lieutenant
Joined: Mon Aug 01, 2005 5:29 pm
Posts:
1
I need some help. I have an rf circuit that I believe has a bad
cable or connector. I have taken a Signal Generator to one side of the
circuit and a power meter to the end side. at one end I need to see
a power level at aboiut -27dBM. In order for me to do that I have to
attenuate the signal using an adjustable attenuator. for what ever reason
I can only attenuate the signal to -13dBM. Any furthur and I lose my
signal. If I take a 20dB in-line attenuator to the end of the cable
I can tune the the power level to the desired dB(-27dBM). I even put
a spectrum analyzer to the circuit and saw the freq I need with the
20dB attenuator in line and saw the signal perfectly. When I took the
in-line attenuator out and went straight through, the carrier fell beneath
a noise floor that was not there when the in-line attenuator in the
circuit. Would this have anything to do with a patially cut cable where
there is still center conductor continuity? Or a bad connector?
_________________
Michael Valfre
Vandenberg AFB
Top
Guest
Post subject: RF ckt behaviorPosted: Sat Aug
06, 2005 11:19 am
Hi!
What you're describing is a classic non-linear
behavior. In general, you get nonlinear behavior from active devices
(like transistors and FETs) and diodes.
You can unintentionally
create a bad diode if there's corrosion between 2 conductors carrying
RF, but it's more likely that there's a bias problem in your circuit
under test.
You haven't given much data on what kind of circuit
you're testing, so the best I can do is the generic vague stuff above.
Is your circuit an amplifier, a variable-gain stage, a modulator, a
...?
Good luck!
Posted
11/12/2012
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