Another set of the odd “billboards” I mentioned earlier are located above Brigham City. So on a trip there today (oil change, plus state-mandated “safety check” for registration renewel), I stopped, for the first time ever, at the tourist info station on I-15 and asked the guy just what the hell they are. His story – which seem reasonable – is that they are “repeaters” for TV signals to hop over the mountains.
You can see the Brigham City repeaters on Google Maps here:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=41.531257,-111.981565&spn=0.000528,0.001203&t=h&z=20
<> The Logan repeaters are here:
<>http://maps.google.com/maps?hl=en&ie=UTF8&ll=41.756879,-111.763712&spn=0.000526,0.001203&t=h&z=20
<>Note that they are not quite parallel. I’m not quite sure just how they are supposed to work. Radio ain’t my schtick.
3 Responses to “Television repeaters”
Sorry, the comment form is closed at this time.
Most of the “billboards” that I’ve seen come in singles, not pairs. I’ve been told that they’re passive microwave reflectors which are deployed when a line-of-sight path cannot be traced between a desired transmit location and a desired receive location (usually due to terrain or buildings which lie on the direct path). In the case of a single reflector, the microwave path traces a “V” shape, bouncing once off the single reflector between source and target. In the case of your offset pair, I’m guessing they’re designed so that the signal path traces a “Z” shape as it bounces off one, onto the other, and then onwards toward the destination. For these pairs of reflectors to make sense, you’d have to presume that a direct path was not possible, which is probably the case if the transmitter and receiver lie at a lower elevation than the offset reflector(s). This sounds reasonable if we presume that the signal is being bounced from one valley location to another with the reflectors perched on a mountain in between. In such a case the Z-shaped signal path is not planar, because both the ingress and egress paths point downward. This implies that the pair of reflectors are canted downward slightly–perhaps not enough to be visible from a distance, but enough to redirect the beam from an upward ingress path to a downward egress path.
That meshes with the one I saw in Japan. It was on a ridge above a big dam which was a few klicks from a town. It was in a perfect location to bounce a signal down into the town. The control station was up at the dam, so I guess the reflector was to do with the alert system for the dam.
I do television for a living, but in the flatlands. It doesn’t resemble any television translator antennas I am aware of, so the “passive microwave reflector” makes sense. I would expect it to be carrying a multichannel cable TV feed instead of just one TV station’s signal to a translator (low power transmitter) site but you never know, possibly the extra expense was worth it.