Tropo On The Ground ... Literally!

My FM antennas are currently down for maintenance and are lying on the grass. The Es had subsided and only the regulars from Spain and Italy were coming through, so it seemed like a good time to carry out the maintenance, which should have taken only a couple of hours. (Ha!)

I had no idea there was going to be a tropo event when I lowered my mast. Funny though, I don't know what possessed me to decide to tune the radio with the antennas lying on the ground, but I did. There were big signals from Hoogersmilde in particular with full RDS, plus many other transmitters coming through from the Netherlands and also Germany, particularly from the Bremen area. These were just about at RDS level.

This got me wondering. Is there an optimum height for an FM antenna above the ground or the roof of a house? Can you go too high?

My FM antennas are usually located on a 6 metre mast at the end of the garden in order to minimise noise pickup from the house, from which there are many sources. The solar panels also generate a little noise but not enough to be a problem.

The south is one of my best directions. During the daytime, I get scatter from French transmitters as far as Strasbourg and Bourges. The east is absolutely hopeless, probably due to taller buildings in the town centre which is only a couple of hundred metres away. Locals from as far as Manchester come through when beaming north-west and Mount Leinster in Ireland is a regular to the west.

During yesterday evening's tropo, Hoogersmilde reached 33dBf on the TEF without amplification!! The antenna was literally lying on wet grass following a heavy shower. It was pointing to the north too! This just made me wonder about possibly benefitting by NOT having my FM antennas quite so high in the future. I will experiment with heights before the antennas are resurrected. I will still go ahead with a slight raising of the antennas with the addition of a new mast extension. It will only add another couple of metres but I was thinking that it will make some difference and should improve the signal-to-noise a little.

So my question is, has anybody else had similar experiences with their FM antennas performing better when lowered?

I also have to wonder what the effect of ground interaction is. Obviously there is a critical science behind this, all of which I am quite ignorant, but I always understood that FM antennas should work better, the higher they are.

Don't you just love these weird little antenna quirks? :O)