In my last post I was talking about the broken PST-61 rotator. The 61 is a strong rotator but not strong enough for the MonstIR. The SteppIR’s are quite rotator hungry, by this I mean that you need a rotator that is rated above that of what you would expect compared to a conventional yagi of similar size.

The flexing or whipping of the SteppIR’s elements cause extra loading at the rotator when it starts and stops and also huge loadings under storm conditions. All this adds up and eventually breaks the gears causing the aerial to windmill.

The only thing to do was to change it out and replace it with the PST 71. This rotator is seriously heavy duty and is designed to turn towers and large 40/80m yagi aerials. The good thing is that the swap is relatively straight-forward.

When using the DC 48V motor on the 61 the plugs at the rotator and controller are physically and electrically the same as the 71. I used the new controller supplied with the 71 but the 61 controller has the same part number so I guess that is the same too.

The 71 is of course larger and heavier than the 61 but the stub mast clamps and rotator fixings are the same. The main difference is the fixing plate height, it is not possible to simply slide the 71 into position and mate up with the existing stub clamp as it is higher.

This is not a problem if you have a bottle jack! Simply put the jack between the cage fixing plate and the stub clamp then loosen off the mast head bearing bolts and jack the aerial up enough to slide the 71 in. The rest is easy as all the fixing bolts align as with the 61. The cage has to be large enough to house the 71 but in my case this was not an issue as there was plenty of room.

All that was left to do was align the aerial and rotator up together and that was it!

So there we have it, the MonstIR is back !!

73 Paul G6PZ