THE TRANSMISSION GALLERY
|Photos by John P Martin||Page last updated: 2021-10-06|
|Glad to bring the first close-ups of this site. Pitlochry is served by two towers: one each side of the Tummel Valley which also carries the A9 trunk road. The westerly tower is referred to as "Pitlochry" on this site (see link below). This easterly tower (Faire Mhor) seems to have been primarily an infrastructure tower built for carrying microwave links. Since then, the usual infestation of GSM panels has taken hold.|
There are no TV services from this tower, the only broadcast services being Heartland FM and the Tayside DAB multiplex. TV and BBC radio are transmitted from the Pitlochry tower, which I haven't yet visited as it's quite a hike!
The public vehicle track to Faire Mhor stops at a gate with five padlocks! After that, it's a 50-minute uphill hike on foot to get to the tower if you don't have keys. This is not an Arqiva site.
While my photos concentrate mainly on the broadcast aerials, there are some interesting oddities which I would welcome more informed comment on.
|You shall not pass! I don't think these are all site-operator locks but those of the landowner: Ballyoukan Forest - Scottish Woodlands Limited.|
|After a hike, you know you're getting close when you see this aptly named sign. Please turn right.|
|First sight of the tower|
|This is a composite view of the entire west-facing side of the tower (ie: the side facing Pitlochry town)|
Aficionados will spot the Heartland FM omni/circular polarised aerial right at the top and the four folded dipoles for DAB lower down on the right. More details follow ...
|Right at the top of the tower, the Heartland FM Band II omni-directional, circular-polarised broadcast aerial. I refer to these as WTF dipoles but I believe they are more properly called Cycloid or SRS (Single Ring Square) dipoles. I think they have since been superseded by even more mystical designs. The co-ax to the stub feeder is clearly visible on the right, but what is the thinner cable and junction box in the centre? My first thought is that it might be to do with heating to prevent icing?|
[Ed]. These band II aerials are made by Shively Labs and there is an option for a deicer with dual setting thermostat.
|The folded dipole on the right is connected to Heartland FM's reserve transmitter system.|
|The two arrays of UHF, 4-dipole arms are characteristic of the AirWave (TETRA) emergency services system.|
|The white vertical colinear on the left may also be part of the AirWave system|
|The purpose of this two element yagi is unknown. At a rough guess VHF high band, roughly 150 MHz.|
|About half-way up the tower are the Band III DAB transmit aerials consisting of two tiers, with each tier comprised of two folded dipoles. These give a cardioid radiation pattern and Ofcom data indicates maximum ERP is slightly west of due south at 195°.|
|Here they are again, seen from the other side.|
|And now an oddity. Very low down on the tower - almost low enough to touch - are these two aerials. Apologies for the poor photo but difficult to photograph from an advantageous angle.|
The square ring is a band I STL receive aerial. There is a similar type of aerial on the rooftop of Heartland FM studios in Pitlochry. See the next picture.
Immediately beneath it is a 3-element vertically polarised Yagi pointing roughly towards Pitlochry town. This is a leftover from some experiments that SSE was conducting with Heartland FM almost ten years ago, using a couple of Trio ER45e to exchange data from their old studios in Alba Place and Faire Mhor.
|A couple of weeks later I found myself outside the Heartland FM studios in Pitlochry. Glancing up I saw this aerial on the chimney. It looks similar to the one at Faire Mhor so I guess this must be the STL transmit aerial. I dashed back to the car and grabbed my little spectrum analyser and found a huge peak at 52.94MHz. Checking on OFCOM’s spectrum map, that frequency is within a band for Programme Making & Special Events Audio Distribution.|
|All aerial cables terminate in the Transmitter Bungalow. On the left is a now disused, older transmitter hall.|
|Plenty of evidence of previous structures on the site. My guess is that a lot of the microwave infrastructure has been replaced with optical fibre. The dishes have remained but previous equipment cabinets removed.|
Corrado Mella, engineer at Heartland FM writes:
That little Yagi is a leftover from some experiments that SSE was conducting with us almost ten years ago, using a couple of Trio ER45e to exchange data from our old studios in Alba Place and Faire Mhor. That's why it's not exactly pointed to our new studios in Atholl Road, like the big square is. I don't know more about it, I'm afraid. There is nothing left connected to that aerial in the rack now, and we're leaving it there because accessing the tower to remove it would cost us an arm and a leg, plus a lot of hair tearing to obtain the right permits. Who knows, it may come useful in the future.
Some additional info for you: the site was originally owned by SSE and was used for their internal comms before it opened up to other operators. It's now managed by WIG. Also on site are Airwave, the Tayside DAB MUX and 4G Vodafone. The shack on the right as you come in was the original safe compound where the TX equipment was held. The leftover foundations between the old and the current compound is where the old tower was, and the leftover concrete slab in front of the new compound had a small garage above it for any vehicle that ventured over there, to protect it from inclement weather while operators were on site.
The dipole that you see below our H/V main aerial is our "B Chain" aerial. We have a main TX on our "A Chain" with an output of 400W (200W in horizontal polarization, 200W on vertical, obtained with that "squiggly" aerial). You are right, the thinner cable on that aerial is the heater. We have a backup 200W transmitter connected to the dipole just below, in case anything in the A Chain fails or we need to do any maintenance on it. There's an active switch in the rack that senses if there's any problem with the exciter, power amp, cabling or aerial and switches over to the backup B Chain. We can see that we're on the B Chain when the RDS signal disappears, because we inject it only on the A Chain.
The colinear is part of Airwave. There's more microwave dishes and other aerials that provide remote control connectivity to the equipment on site for all the other tenants and interlink with other towers. Good spot with the rectangular aerial, indeed it's our FM 52.925MHz uplink.
Originally our TX aerials were halfway through the mast, but when the Airwave riggers went up and their body worn RF monitors started screaming that there was too much radiation where they were, we were demanded to put our "thing" up at the top. Happy to oblige as they paid for the relocation and that extended our reach by a good 5 miles. We plan to upgrade the STL from the analogue FM mono 52.925MHz to a digital point-to-point 5.6GHz microwave link, both to feed a low latency audio stream with all the Now&Next info to push out via RDS, and to bring all the TX equipment in the rack to connect back to our studio network. But that's for the future.
|Finally, and separate from the tower, is what appears to be a low-gain EHF parabolic dish pointed to the zenith. Maybe it monitors the Cosmic Microwave Background radiation. It is obviously quite new and replaces a number of now redundant discone aerials.|
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