DB Products Dual Stage Isolator

This Decibel Products isolator is used on the output of the 90 watt power amplifier. These isolators have been readily available at very low cost, presumably from surplus paging installations. They are dual stage, with a built-in load on the low power isolation port.

Network analyzer plots of the isolator.

As can be seen, the isolator has less than a .25 dB of insertion loss, an input return loss in excess of 35 dB and isolation in excess of 60 dB.

The output stage isolation port of the isolator is connected to a 100 watt dummy load as shown here.

The load has a very good VSWR in the band of interest.