I have used this device before a long time ago in projects designed by other people without problems.

I am now trying to build a project myself & have struck a basic problem.

The project is a home made Spectrum analyzer and I am trying to mix L.O of 15Mhz (approx) with the output of a video I.F strip of 39Mhz as RF feeding a xtal filter of 21.4Mhz.

My problem is with the L.O.

The specs for the SBL-1 states that I need +7dbm and the input of the device is 50 ohms.

I can generate enough 15Mhz approx 2v p/p (+10dbm) as measured on a scope.
I then knocked up a 3db 50 ohm pad and terminated it into a 50 ohm load and all worked approx 1.4v p/p across the load.(+7dbm)

Next step is to remove the load and connect to the SBL-1 (pin 8) via the pad and the levels drop considerably to about 0.75v p/p +1-+2dbm with a little distortion on the +ve peak.

This seems to indicate to me that the mixer input is not 50 ohm but a lot lower. I tried terminating all other ports with 50 ohms with no noticeable difference. What am I missing?

Why can't I see the correct level in to the device. I have plenty of drive before the pad but it reduces when connected to the SBL-1.

I am missing something. Can anyone prompt me?