Not sized properly. Transmitter is sitting on a pretty tall pole right now and getting it off is a bit of a hassle. And I also already covered cap with a glued heatshrink to protect against elements, so accurate measurements are not possible without destroying it... But I hope it can give an idea what I came up with.
I'm pretty curious if you could sketch something up.
Sounds like you might have inadvertently created a wave guide.
If you are feeling adventurous you might want to try dropping your creation into an Antenna Simulation software like NEC or something similar.
https://www.xnec2c.org/
https://imgur.com/qelKWpL
Here is youtube video someone fixing broken unit to get an idea what it looks like inside - https://www.youtube.com/watch?v=-k_6NsqFAdc
Not sized properly. Transmitter is sitting on a pretty tall pole right now and getting it off is a bit of a hassle. And I also already covered cap with a glued heatshrink to protect against elements, so accurate measurements are not possible without destroying it... But I hope it can give an idea what I came up with.
Thanks for the link to the simulation tool!