Jerry Martes wrote:

I'd have expected the "gain" to be closer to 4 1/2 db over the 1/4 wave
stub over a ground. is it easy to show where i've missed something?


I think it should be more like 3 dB, but hadn't said anything until I
had a chance to model it. The quarter wave stub doesn't radiate
significantly, so it can be ignored. A half wavelength element should
have about 1.5 dB gain over a quarter wave. Two of them would give
another 3 dB if it weren't for mutual coupling, but the mutual coupling
of collinear elements reduces the gain to about 1.5 dB over a single
element. (See for example Fig. 39 on p. 8-35 of the ARRL Antenna Book,
20th Edition; look up Collinear, Gain and directivity in the index of
other editions; or model it with your favorite program.)

Roy Lewallen, W7EL