Here are some passive reflectors used by the BBC. The UHF TV transmitter at Eitshal in the Outer Hebrides is fed from the Rosemarkie transmitter 160km away on a combination of active and passive repeaters on 7GHz. Due to the remote locations in the far North of Scotland there are 2 passive sites to save on the huge costs of running electricity to them and also building and maintaining relay stations.
This passive reflector is at Glenmarksie, 3.6m x 4.8m in size.
I think the reason they are not in wide usage is an inherent 30 dB loss. Two Yagis can make up half of this and the resultant signal is still sufficient in the valley. Dish antennas have more gain which helps but the usable footprint is small.
Drive in theatre size billboards are good but their exposed location requires extreme strength. They reflect backwards so only feasible if on the far side of a deep valley on a higher ridge.
Active repeaters do a much better job which is why people go to the trouble of installing them.
You’re spot on. This example was from 1976 when a pair of 7GHz RX/TX would have need a 2x 6ftx19in racks and a building and power and telemetry. I’m not sure if there were any viable solid state PAs then but now you can make a 7 or 13GHz RX/TX with a few watts out and 0.5db NF that will be smaller than an 817 and can be run from solar / wind power.
Some context, here’s a view of the back to back dishes showing the kind of country they’re located in. Also they’re about 500m ASL and about 150km North of Moscow so you can imagine what the WX is like here in Winter
This link provided sufficient bandwidth to provide 4x PAL colour TV channels and many audio carriers. I don’t know if it still is used especially with the move to digital TV in the last 15 years. Considering where those dishes are located, they’re a damn fine advert for the durability of the products Andrew Corp make along with the engineers who installed them 45years back!
While we are considering odd installations. This one, just below the summit of Beinn an Turic, intrigued me. In particular the small unit (TRX+antenna?) which seems to be pointing up at the summit. Ideas?
Gerald and I saw an almost identical enclosure complete with ground-observing CCTV camera on one of the other SS’s surrounded by a windfarm - might have been Common Hill SS-174, I’m sure Gerald will know for sure…