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# RF input

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#### jwga14

##### Newbie level 6
When connecting to amlpifier input there is a - 10 dBc coupled sample RF input (why).
When connecting to amplifier output there is a -40 dBc coupled sample RF output (why).

I would guess the amplifier has a gain of 30dB. It would be to keep the power at each sampler output the same for both input and output.

Thanks G4BCH
I am new for the following abbreviations
what does it mean exactly

 Spurious(@ rated P1dB) is -70dBc Harmonics @ rated P1dB-3dB is -40dBc
Linear group delay
Parabolic delay
and Ripple group delay

P1dB is the power at 1dB compression i.e. when the output power is 1dB below what would be expected if the amplifier were perfectly linear
-70dBc means that the spurious outputs will be 70dB below the output signal. -70dB relative to carrier power.
The harmonic spec means that the harmonics will be 40dB below the output signal in the range where the output is between 1 and 3dB below whet would be expected if the amplifier were linear.

For explanations of group delay search google there are many hits including YouTube videos including here on edaboard https://www.edaboard.com/threads/some-questions-about-group-delay.55960/
It is basically the signal transit delay through the amplifier. If there is a filtering function then there will be over the useable bandwidth an area where the delay will decrease flatten then increase again in a parabolic form see
https://nardamiteq.com/docs/14TEC.PDF
for some diagrams. This will be the parabolic group delay usually given as a maximum deviation that can be allowed. Sae with the ripple which cab be any shape. The deviation from linear is what defines the phase and time distortion that a signal will undergo as it passes through the amplifier. This will also change with power level.

Hi,
I have another question concerning the amplifier gain flatness limit.
What does it mean gain flatness limit is C 1.0 dB?

I don't know what the C means here. may be it means circa, or about. The gain flatness is usually quoted as
+/-xdB max. This would be over the usable frequency range n within the linear power range, not at compression.

I don't know what the C means here. may be it means circa, or about. The gain flatness is usually quoted as
+/-xdB max. This would be over the usable frequency range n within the linear power range, not at compression.
Thanks , It was noted in the testing sheet gain flatness limit is C 1.0 dB.
VR

I have another question / expiation
Input overdrive : 3 dB ? meaning
AM/PM conversion @ rated P1 dB max limit is 3.5 o/dB?
AM/PM conversion @ rated P1 dB -3 dB max limit is 1.0 o/dB?

Thanks

Input overdrive overdrive of 3dB is 3dB beyond the rated input level. I.e the amplifier output will be going into saturation. It could also mean that the amplifier is capable of surviving an input level 3dB above the maximum specification value.
The first AM to PM conversion spec means that the transmission phase shift though the device will change by 3.5 degrees for every 1dB increase in power above the 1dB compression point
The second is not that clear but looks like the phase will change by 1 degree per dB increase in power in the range from 3dB below the -1dB O/P compression point to the -1dB compression point.
These values are not atypical for a power amplifier.

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