In the 80's, when I was 12-13 years old, I used to be a CBer, with a little legal transceiver by CTE International, model SSB 350, and a "Skylab" antenna. I remember that such antenna was advertised as an outstanding gain one, up to 7 dBi, or something like that. Today, I took the opportunity to verify with NEC2 if the gain of a Skylab is actually so good. Here you are the outcome of my investigation...
Well, the gain is that of
a normal Ground Plane 1/4 wavelength antenna. 
Once mounted on a 6 meter mast (which looks a reasonable height for an average CB installation) it results into a 1.7dBi gain, with a take off angle of about 16°.
In the free space, the simulation shows a maximum gain of 2.37dBi.
The same antenna model is also advertised in a fair way, under the name of Starduster M-400, by promising a 2.1dBi, which is a much more realistic value in the free space.
I liked my Skylab so much, but now I realize that it was just a basic antenna 
.
How bad is becoming an adult? You find out that Santa Klaus does not exist, that the Skylab does not gain 7dBi and that, unfortunately, Epiphany (crone) are more than one...
