Sorting out RFI on my Rockmite 80m QRP rig

When I heard that Dave Banson had announced his decision to close Small Wonder Labs, I decided to press my Rockmite 80m rig back into service. So I connected it up to my long wire antenna and turned it on.

What I heard was a local commercial station booming in real loud. And no amount of tuning would get rid of it. I even connected up my NesCaf filter to see if that would do the trick, but it didn’t.

I consulted the rig’s instruction sheet once more and sure enough, Dave had foreseen this problem and suggested a fix. All that was needed was to install a 1K resister into the two unused pads immediately below D1/D2 on the PCB.

That called for the PCB to be removed from it’s nice enclosure, an Altoids tin.

The PCB safely removed from the Altoids tin enclosure.

The PCB safely removed from the Altoids tin enclosure.

 

The two unused pads can be seen below the two diodes on the right (middle) edge of the board.

The two unused pads can be seen below the two diodes on the right (middle) edge of the board.

Once the resister had been soldered into place, it was just a matter of putting everything back together again.

Everything back snugly in the Altoids tin and ready for use.

Everything back snugly in the Altoids tin and ready for use.

So how did the rig now perform? Nicely, although the offending station is still slightly audible. But not enough to bother me. I must add that some nights I can’t hear it at all.
All I now need is a QSO. I call CW every evening in the hope of a contact but so far this has proved elusive. The 397mW output makes this a challenge, but this is what the fun of QRP is all about. It will come.

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2 thoughts on “Sorting out RFI on my Rockmite 80m QRP rig

  1. Hi Grant

    Well I have been using my FT817 and IC703 recently. So your mail was a reminder that I should get out my Pixie II. It uses a crystal from an old TV set so is stuck at 3.579. I never found the rx part to be too great but I think I last used it in Durban over 6 years ago.

    What frequency is your Rockmite on?

    Now that would be a real fun thing for us to have a qso on our QRPp rigs

    Ian ZL2AIM

    • Ian, my Rockmite is rockbound on 3.560 mHz. It puts out a measly 397mW with a 12v gel cel supplying the current. I measured this pretty accurately with a QRPometer as well as a Hendricks dummy load/power meter. If I connect up the PS and pump 13.8v into it, I can squeeze out 612 mW. Do you think we can make it across the Tasman with this kind of power? Conditions would have to be excellent.

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