I have used the 14AVQ antenna and it is a good antenna.As far as putting it on a 40' tower I really don't feel it would benefit you any.Even if it was mounted onto the tower you still need radials for the antenna and you might run into tuning problems.With a vertical you really need to use guy ropes as it could be easily snapped by the wind that high in the air.If you have the yard space and can mount the antenna on the ground I would highly advise it.All you need is a pipe driven into the ground as per the instructions. Then go to your local Lowe's or Home Depot or somewhere that sells stranded 14 gauge insulated (preferably green color)copper wire. Cut the wire into the needed lengths as per Hy-gain's instructions and put a ring terminal onto both ends to fasten the wire to the vertical's base. Alternately you can go to DX Engineering's website and get a radial plate and a tilt over plate for the Hy Gain series of verticals.
Once you have the radials cut and a terminal on the ends connect them to the verticals mounting base or to the radial plate and fan them out pretty evenly spaced if possible (use a sod staple at the very end to hold down the end of the radial. As you install each radial you can use sod staples (found in Wal-Mart's lawn section) or again through DX Engineering.You can also make your own using stiff solid wire.The purpose of the sod staples is to "tack" the radial to the ground low enough as not to interfere with a mower or kids. In time the grass will grow over the radials and you will never know they are there.Another way to put down the radials is to bury them about an inch or so into the ground by whatever means available.I have laid mine down and used the sod staples and the radials have never been harmed by a mower.
When I had the 14AVQ I had gotten it used from a local ham. I think one trap was not in good shape so I replaced it and polished up all the joints with steel wool. I set the antenna as per the instructions and installed it on a 5 foot Radio Shack steel mast driven into the ground and tacked on a radial for an air check. I worked a couple of Brazilian stations with it on SSB (this was in the mid 80's)from my QTH in Independence MO using a TS-520S. I ended up selling it to another ham and now use a 6BTV made by Hustler (also a used antenna).
Would I use another 14AVQ (or even an 18AVQ-WB)?Yes.The antenna is a good quality one and I like it because of the small "footprint".I do highly recommend putting one set (3 ropes) of small diameter guy ropes on the antenna. No vertical can withstand extremely high wind and with guys it stands a very good chance of surviving.I have 2 sets of guy ropes on the 6BTV due to the large resonator (1 KW rated) on the top of the vertical.But with the 14AVQ only one set is necessary.This fall I plan to put more radials down, retune the antenna, and install the tilt over plate and radial plate.
Sorry to be so long winded over the subject but hope that you can use this information.You don't need a KW and a beam or vertical on the tower to enjoy the DX (even at the bottom of the sunspot cycle).Good luck and you can email me at email@example.com