[Test-Equipment] No luck with sweep markers

[RJ Mattson]

I am successfully sweeping a 455 kHz IF strip with a Wavetek 134 and T935 
scope.
The scope waveform trace looks typical for 455 kHz with a 10x probe or demod 
probe.
With an external adjustable rf generator I am trying to inject a marker to 
determine the center freq, band width, etc.
As I move the marker sig gen through 455 kHz, all I am seeing is a sinewave 
superimposed all over the scope bandpass outline trace - no pip marker.
I have tried different injection points, sweep widths and sweep time with no 
result.
Any suggestions?
Are injected markers only visible with higher frequencies such as wide video 
IF's?
I read an article where they suggest the best way to use markers is with a 
"post injection" circuit ?

bob...w2ami