On Wed, 18 May 2005 19:04:44 -0400, chuck wrote:

I'm in the market for a used spectrum analyzer like the 7L12
or the HP 141-T. One important use will be to make two-tone
IMD measurements on HF SSB transmitters. I am concerned that
with tone separations on the order of one kHz, the 7L12 may
not have sufficient bandwidth in the 300 Hz mode to resolve
adjacent IMD products expected to differ in amplitude by 40
dB or more.

Has anyone on the group used a 7L12 for this purpose and is
the 300 Hz RBW sufficiently narrow?

There seems little doubt that the 141, with 10 Hz or 100 Hz
RBW, will handle this.

Many thanks in advance.

Chuck
NT3G

I have never played with a 7L12 but do have a 141t. 300hz bandwidth
will work. The best resolution on the 141t is 100hz. There is a 10 hz
video filter but the video filter does no good for resolution. It only
gets rid of noise. The biggest problem that I can imagine with the
7L12 would be whether or not your scope has some kind of storage or
long persistency on the tube. To look at 300 hz bandwidth you need a
very slow sweep speed on the scan. If there is no storage you will not
be able to see it.

73
Gary K4FMX