I believe its on crosstalk -
What causes the spike at roughly 15.2955 MHz ?
Start .3M Stop 1GHz spec -100 - on one or two of the crosstalk checks there is always a upward moving spike starting at .3M and peaking at 15.2955 MHz (about). This is also seen on the 8753ES with or without opt 006.
I'm thinking its the response of a specific internal component but these things I wonder.
What causes the spike at roughly 15.2955 MHz ?
Start .3M Stop 1GHz spec -100 - on one or two of the crosstalk checks there is always a upward moving spike starting at .3M and peaking at 15.2955 MHz (about). This is also seen on the 8753ES with or without opt 006.
I'm thinking its the response of a specific internal component but these things I wonder.
The 8753 has a change in receiver operation that occurs at 16 MHz. Below, it is a single conversion receiver, and the RF sampler is put into a bypass mode. Above, the RF reciever samples and down-converts to a fixed 1 MHz IF.
Below 16 MHz, the signal is reconverted by an IF mixer, and the LO drive does have some spurs on it. Thus, these spurs show up as signals. Technically, they are not crosstalk, as they are not of stable phase, and sweep to sweep averaging will remove their effects. They are "spurs". And, in the manual, you will notice a little foot note about "Spurs at some frequencies below 16 MHz"