Antenna Issues

I have been working to optimize the communication antenna installation on the Cub. My home airport has significant transient traffic, so a good radio is a must for safe operation. I started with just the short antenna that came with the radio, however that had limited range and a tendency to feed back through the microphone wiring.  I had purchased a dipole antenna for my Taylorcraft and could never get it to work properly. It was installed in the tail behind the cockpit. I still had it so I thought I would give it a try in the Cub. Here is a link to the antenna web site.

 http://www.advancedaircraft.com/

To make a long story short, I have tried this antenna vertical, angled right , angled left, angled forward and back, side ways, and curved in every direction . In every case the reception to the sides is great but the signal is blanked directly to the front. The only place it will fit due to it's length is behind the seat in the fuselage.

The combination of tubing , pilot, passenger, engine, fuel tank, and firewall, must shield the antenna from any forward signal. You can turn 15 degrees left or right and receive a usable signal.
My test procedure is to takeoff from KJGG and climb to 1500 feet and tune the ASOS at KAKQ 20 nm away. I then execute a slow 360 degree turn while monitoring the signal. In every case the signal is blanked to the front where you need it the most. On my Taylorcraft I gave up on this antenna and installed a bent whip on the bottom of the boot cowling.
On the Cub this would be more difficult because there is no access to the inside of the boot cowling to install a proper doubler and to attach connectors. It took some brainstorming but I finally figured out a method. I decided to attach the antenna directly to the bottom of the forward floor boards, all the loads would be absorbed here. The physical antenna would protrude through a small hole in the lower boot cowl. Here is the attach bracket I came up with, it's formed from 0.040  2024-T3 aluminum.

Using a 2 inch hole saw I cut a hole in the forward floor boards.

Here is a shot of the completed mounting bracket with nut plates installed and a coat of alodine.

 
With the help of my friend Scott , we figured out a process to install the antenna , add the insulator, install the bracket, and tighten it all up. It was a slow careful process because anything you drop is a frustrating exercise in fishing to recover. If it's not magnetic you have just lost and hour.  Here are some shots installed. Once the wiring and testing are completed I will make an aluminum cover plate and remove the AN970 washers, painted black you will hardly notice it.

The safety wire is the path the antenna wire will follow under the floor boards. Here are some shots outside.

I'm not sure how this will work with the landing gear so close and the limited area for ground plane provided by the narrow boot cowl. It was an improvement on my Taylorcraft so I'm hoping for the same here. I would settle for being able to transmit and receive in the direction I am traveling. I hope to wire and test this on Friday, tomorrow is my father's 91st birthday!