Position of feedback loop injection resistor for SMPS loop measurement?

[Flyback]

Hello,
In the below schematic (LTspice sim also attached) is R7 a good place for test signal injection for measurement of the feedback loop gain and phase margins (bode plots) with a frequency analyser (eg AP300 by Ridley)?

 

[simonbramble]

It looks OK. As long as it is in the loop, it should be OK. Attached is a circuit using the .measure statement to analyse a buck converter gain and phase margin in LTspice. Takes a while to simulate

 

[simonbramble]

... and by the way, it is RD Middlebrook who pioneered this. Ridley just made the instrument to measure it... if you want to read up more on this. Venebles' paper on the K factor is also worth reading

 

[Flyback]

It looks OK. As long as it is in the loop, it should be OK

Thanks, though R3 and C2 are 510R and 33n respectively....this makes the impedance of the upper divder impedance too low for a successful measurement?
The injection resistor must "see" high Z one way, and low Z the other way, I thought?