A while ago I wrote about a helical filter that I had made to reject pager interference on 2m. I was curious to see how stable that was over time. To test it, it has been carted about all over the place, dropped, knocked and otherwise abused. Yesterday at the G-QRP Convention I finally got round to retesting it. To my great surprise, it has not drifted at all and the peak is still at 145.5MHz.