Hi all, i am new to this site and have been off air for years now, hoping to make a comeback.
anyway i have an old A99 lying around and was wondering if anyone had ever screwed a mobile whip, firestick, dv27 etc, into the top section instead of the a99 piece to make a better performer 5/8 or 3/4 wave etc, plus it would be top loaded?? any thoughts?........jim

Considering that the mobile whip is already designed to present 50 ohms to the coax center and braid to ground plane, I dont think it would work that well.

If you sent the coax up to the whip and the centre went to the whip and the braid went to the antron below it acting as a ground counterpoise of the correct length it may work.

But if you just feed the A99 as normal and attach the whip up the top I doubt it.

Then again, antennas can behave in strange ways sometimes!

get a fire stick a red one ?? and tune your rings it defo works there are a few here in the uk they work very well

Well looks like I was partially wrong on this, - never considered retuning the ring to suit the new impedance the top mounted helical whip would present.

I would have thought that the extra wire length would move the centre freq down the band though into 25,000MHZ just like adding a longer top section?

Anyone done this and had successful results first hand?

Hang on a sec...the A99 is a 1/2 wave, in theory about 18' high. It comes in 3 sections approx. 6' long. So by taking off the top section you are physically shortening the antenna. OK you put a Wilson Firestick on top and tune....may work may not. I don't think there is a 6' firestick the longest is 5' from memory...don't rely on that. Either way it will be nowhere near a 5/8 which is approx. 24' high. might be better to bite the bullet and purchase an Imax 2000 which is a .64 wave and a better antenna than the 99 ever was. Just my experience.
Regards,
Bob.