Once the GXP antennas were up,
there was time to test the SWR curves.
20 and 10m were fine but in all antennas the resonance on 15m was too high, with SWR at 21.00 MHz > 2:1.
The 15m element was too short and needed to be extended by about 10 cm.With the boom screws loosened, the antenna could be rotated on one side only as the transmission line was hitting the other the other way.
I extended only one side of the driven element by 10cm for both 11-4, and now the SWR curve was fine.
I still need to do that for the 17-4 antenna on top.
Another problem is a narrow bandwidth of the 17-4 antenna on 40m. While it is low in the CW band, it is 2:1 at 7.15, and 3:1 on 7.2. I plan to add a switched matching circuit to make SWR low in the phone band. On 7.2, the impedance of 115-j65 can be matched by an L circuit with a coil of 1.5 microH and a cap of 320 pF.