High Z Antenna Amplifier - intermods

Nick G4IRX


I've just received a pre-owned High Z amplifier which I suspect is faulty. I found a noticable intermod on 198kHz in place of BBC R. 4. I have two local MW TXs on 1197kHz and 999kHz. 1197-999=198. For some reason it's behaving as a mixer rather than an amplifier.
I also have an LAA+ and Wellbrook ALA1530, neither of these show this problem. Has anyone else with a High Z observered a similar problem?


Chris Moulding

Hi Nick,

Check that the jumper JP1 is still in place.

This adds a pair of silicon diodes across the output to help protect over-delicate SDR receivers.

Cut the jumper and you will get the full IP3 performance of the amplifier .