Is the Top Hat the upper tubes you refer to Bob?
I've noticed some old ads showing atrist renderings that look like the A/P with different Top Hat construction, maybe using tubing instead of SS wires like your antenna. The SS wires remind me of the wire tips on the Moonraker.
The model I made using Tib's dimensions shows resonance of 27.1 at the feed point. If the model is close to accurate the A/P antennas you and Tib have were probably pre 1979 and were still being cut for 23 channels. I think the 40 channel idea came up about that time or maybe 1976-1977.
I have an old HyGain SP500 manual dated 1975 that shows they were still making their antenna for 23 channels. When they went to a 40 channel design they added 3" inches to the radiator. They also made changes in the tubing distribution for the radiator over time. Mainly making the tall base section smaller at some point.
My last CB Magazine is dated Jan 1976 and all the radios were 23 channel models.
The ad below from CB Tricks is noted to be dated Feb 1978, and this antenna is for 40 channels according to the specifications. However the article itself shows copyright 1977. Some of the text is missing and I don't see the model noted as AV-101A and this one is the last ad in a string of ads on the CB Tricks Website.
I would be interested to know if Avanti made any adjustments to the dimensions after the 40 channels came out?
This is not history and does not answer much...the dates are probably off a bit.
