Cylinder dipole PA1B
This coil has 9 turns on a PVC tube with a diameter of 80 mm. The distance between the cans is equal to the diameter of the cans and is 65 mm. The distance between the cans is not fixed, but can be made smaller by shifting the cans.
On both sides of the coil I have attached a single turn, coupling loop. The loops are lightly coupled to the coil. One loop is connected with the RF generator. The other is connected to the oscilloscope.
It's very simple to measure the resonance frequency of the cylinder dipole. By adjusting the frequency, I just peak the signal on the oscilloscope to determine the resonance frequency.
The cylinder dipole with the open Monster cans and the 80 mm coil with 9 turn, resonates at 18.9 MHz. This is a higher frequency of the closed monster cans, which resonates at 16 MHz. The capacity of the open can is lower than the capacity of the closed cans and also because the cylinders are further apart.
I use the Cylinder Dipole on 21 MHz and 14 MHz as an indoor antenna in CW contests.