Hello Doc...
The antenna is easily modeled in EZNEC. When I built the first one, I had to make just a small (~3%) adjustment in the overall length vs. the modeled length to get it to resonate. That was almost certainly due to a variation in wire size vs. the model.
The major difference was in the bandwidth. EZNEC said it should have about 1.8 MHz 2:1 bandwidth for 10M. It actually covers MUCH more than that.
There are no impedance matching devices. IOW no gamma match. No inductors. No capacitors. No transformers. Just PVC and metal.
The coax shield goes to the Metal cylidrical outer conductor. The coax center conductor goes to the monopole that runs from the base, through the cylinder and upwards.
The total heigth of the antenna is just under 1/2 wavelength -- call it 3/8 wave or thereabouts. The metal sheath is roughly 1/8 wavelength.
The antenna is a bit unbalanced, so I strongly suggest that either a 1:1 current balun be used (or several ferrite beads) to keep any common mode currents from making their way back to the shack.
As I mentioned earlier, I have pictures , but I haven't figured out how to post them! :-(
Let me try this... here's a picture of the antenna on the back deck. The box at the end of the cable is my MFJ. It is battery operated and the only connection is to the antenna. http://www.worldwidedx.com/members/kt4ye-albums-searchlight-picture3541-searchlight-sept-30-001.html
This is the MFJ reading at resonance: http://www.worldwidedx.com/members/kt4ye-albums-searchlight-picture3571-searchlight-sept-16-005.jpg
This is the MFJ reading at the lowest frequency: http://www.worldwidedx.com/members/kt4ye-albums-searchlight-picture3573-searchlight-sept-16-003.jpg
This is the MFJ reading at the highest frequency: http://www.worldwidedx.com/members/kt4ye-albums-searchlight-picture3574-searchlight-sept-16-004.jpg
Bill
