The Mystery of the Increased Range

@artisan-radio I just right now put a long sheet of aluminum foil on the shelf where my set up is. The shelf is 10 & 1/2" wide and 43" long but covered 3/4 of it so the laptop is not on the foil but the Decade and the Schlockwood is along with the audio cables .. audio from the computer, and audio to the Decade. Some of the audio cable from the Schlockwood is hanging over the edge of the shelf as before in the same position. Everything exactly positioned as before, the Decade antenna exactly the length I had before and angled as before in exact position. The Schlockwood sitting inbetween the computer and the transmitter as before but now on top of the foil.

OH...MY...GOD!  This is scary. I first measured the signal off the antenna with the hand held signal strength meter and the pointer shot up to 1 and a half times the signal strength it was before, took a range check in car and WOW! Big difference in all the fringe areas
I will post the picture later showing the foil covered shelf. The Decade is as you know the older plastic case ones. Some, a bit, of signal was radiating from the section of the foil farthest from the transmitter. All harmonics were the same...good...not affected by this at all.

This has to be a version of what I accidently ran into with my Decade antenna and WH3.  I'm actually a bit surprised it made that much of a difference for you, but on thinking about it, you're dealing with VHF frequencies, where antennas and ground planes can be smaller.

I guess you'd get the same effect by placing the transmitter on top of a metal cabinet, or desktop or shelf.

So now there's an interesting situation.  The rules don't state where a transmitter can be placed.  In talking previously with ISED, they expect it to be used "as intended" (i.e., they might frown on you mounting it on top of a rooftop in a waterproof box, because that isn't how it's designed to be used - but it's certainly intended to be used indoors on a surface, surface not defined). The Decade is certified.  Obviously the field strength has been increased, but if you don't have that expensive measuring equipment (which certification is supposed to make not necessary), you don't know if you're over the limits or not.  IMO, you're using it as intended, and it's OK.

I'll perform the same experiment with the WH3 and report back.  I wonder how the results will compare with what I originally noted?

@artisan-radio As I noted the section of foil at the opposite end of the Decade is radiating also. I just created a better ground plane or, the other half of the  antenna.
You could put the transmitter on top of the refrigerator also. I don't know if I will leave it like this though.
Here's what I did. The shelf is wood, I just created a metal surface. I think if I took the Schlockwood off the foil it wouldn't matter. It's not a factor in this. But if I ever got inspected the first question would be why is the foil there....well, what would I say.