[R-390] Image problem cause... sort of

[Tony Casorso]

I believe I have a handle (part of a handle) on my image problem. I compared the preselector selectivity of my R-392 to the R-390a and the R-392 is way way better.

I put in a signal from the generator on the balanced antenna input and put the spectrum analyzer on the grid of the first RF stage through a 10x probe and a small capacitor. With the generator at 1.5 Mhz I tune the receiver to 1.5Mhz and peak the antenna control. I note the amplitude of the 1.5MHz signal on the analyzer and then tune the reciver to 3 MHz. On the 390a the 1.5MHz signal drops less than 20db. On the 392 it drops over 50db.

I also note that the peaking with the antenna trimmer is much sharper in the 392 than with the 390a.

I want to look at some other bands and see if it is like this everywhere.

Tony