It looks like the Microvert antenna may have originated in Japan? The Microvert is a very compact antenna. Some believe the coax is a major part of the radiating system. Having never tried this sort of antenna I am unable to comment. This was posted to the Microvert Yahoo group earlier:
Whether you believe it’s the coax radiating or not, this is still interesting:
There are other websites about SRA (secondary radiation antenna), but unfortunately all in Japanese. Its definetly a Japanese thing!
I have all the parts required here to make one of these. Whether you believe its the coax radiating or not the results will be interesting.
PS. My old 10m/12m modified microvert gives a good SWR.