Naw it'd be less than 3 Metres give or take, 7 1/2 waves including the matching stub and a 1/4 wave to attach it to the mast.

The 70cm "super-gain" version is just over 11ft long including its mounting spike. It has a fibreglass rod up the middle for rigidity and after many hours of tweaking, we got the SWR down to almost immeasurable. The omni-directional gain is of the order of 10dB, meaning that the 20 Watts carrier power gives about 200 Watts ERP. There's little signal beneath the aerial, and there doesn't seem to be much going upwards - the energy is where you want it!

The Band II version of the Super-J outperforms a pair of stacked dipoles. I also tried a version with a groundplane, which worked quite well, but the effort of adding the radials wasn't really justified by the very slight reduction in downward radiation.

One example of the Super-J remained up a Central London block for several years - it was disguised as a CB aerial. A number of stations used it over the years, usually with good results. It was built for 105.5MHz (before the infestation of that part of the band with the commercial rubbish) and worked really well!

Other verticals I've built and used:

The NRG ½-wave - works well, but difficult to get a good match because of the bizarre feedpoint impedance of a ½-wave. Stephen's improvised capacitive match worked OK up to about 80 Watts, but could easily flash over at higher power.

The ⅞-wave vertical with groundplane radials - great from a lower site, and has useful gain.

The ⅝-wave vertical with radials - can get a reasonable match over a couple of MHz and has a bit of gain over a dipole. Needs a loading coil at the base for best results.

Both the above had the coax running down the inside of the mast to prevent the "pins in the coax" vandalism perpetrated by a couple of competing stations.

I also built and used (just for one Bank Holiday) a vertical sleeve colinear that was about 22ft long. It really flew, but was a complete bugger to install up the block. We needed guy lines and about 10 people to get it up!

a silm jim/j pole shouldn't be more that 2.5 meters tall! if you use a higher frequency it will be shorter

i managed to get a j pole working on the floor the other day using bits of alluimium a wire at the bottom to connect to the shorter element, i've found there needs to be some spacing even thought it said on the website it was not critical, few cms, problaly why using speaker wire didn't work..I stopped messing with it for now as i've been playing with a gp instead.

where do we find info how to build the 7/8???

Isn't the 'Dominator' supposedly a ⅞?

Albert H wrote:I've also built them with two or even three phasing stubs so that they have insane amounts of gain

So what sort of gain could you expect with 2 or 3 phasing stubs on a normal J Pole?

I went looking for the "good stuff" on this antenna, but found Mark Weiss' website AMN92 is gone, so I dug it out of a folder and banged it up on the web again -
These things are finnicky, if you don't get resonance in the folded stubs then you may as well use a regular J-Pole, I tried dicking with a suitably bent wavelength of stiff wire tacked on to a copper pipe J-pole but could not get it to go, I think the different diameter materials might have been to blame though. He claims 8.8Dbi gain off his 4 element version, shame that site is gone it had a few nice bit and bobs on it.

yellowbeard wrote:I went looking for the "good stuff" on this antenna, but found Mark Weiss' website AMN92 is gone...

Do you have the original web address to hand. I remember his site too, and want to try and get a mirror of it for myself from the "wayback" archive.

Been there and tried that Dai - a lot of the pictures are missing, but here it is anyway:

Cheers, and thanks anyway. I'll still give it a go, even if it's just the text.

I heard there was a new modified version of the Super J-Pole.

It's called the Super Jay Xtreme Pole.

i built a jim/j pole whatever their called 2 weeks ago, i put the top at the same height as my gp antenna, it was easy to tune i got perfect swr lower than the gp. the signal was about the same! and actually seemed to dissapear in some places, it could of been the aerial made out of wire, then when i started with my gp the radials where made from the same wire! not good