I tried the centre fed dipole backpack antenna at the Guy-Fawkes 10, having seen Mike do well with one at the Sunrise Walk. Mine was home made and I think suffered water ingress in the pretty poor weather. Signal to and from Control deteriorated over the course of the event.
Fortunately I was able to reach Control using a standard 1/4 wave antenna on the handheld from my location, which means in retrospect (and next year) I’ll do the whole duty on a stock antenna.
I’ll have to upload a photo of the 1/2 wave I used. It is made of two lengths of RG213 with the braid connected to centre and shield of the RG58 feeder. The wide cable gives it quite wide bandwidth. This is fed into 15mm plastic water pipe and a 32mm plastic drain pipe is glued to the side at the centre point. A choke is wound around the drain pipe using the Flowerpot tables to give number of turns to self-resonate in the 2m band.
I don’t know how best to measure or test this self resonance. I believe the antenna worked well before it got wet, though I didn’t compare it dry against the standard antenna. I was able to talk to Control from home and hear Control during my cycle ride to the event.