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Photos by Dan Glover Page last updated: 2017-05-20

February 2017: DAB and FM changes

Visiting the same site every few years should make it possible to build up a nice set of "before and after" photos but somehow the lighting and perspective never turn out quite right!

Expected changes since August 2014 were the addition of D2/SDL and the replacement of the Radio Clyde array. As before at Black Hill things aren't always as they first seem.

Ideally we need someone to go back on a bright day and do another "full survey" of both masts - mid February is probably not the ideal time.

Starting with the "new" mast. Built in 2008 for DSO it was at one point thought it would be a replacement - but it now seems there is no plan to migrate services from the "old" structure. At first glance nothing has changed since 2010...

...however there used to be a small DAB antenna between the two television arrays (see inset). This was thought to have been for the Glasgow local MUX. Although the perspective is different it seems this has been removed.

A new DAB array has been added below the platform - this is for SDL (BBC and D1 are from Kirk o'Shotts)

We hope a quantity discount was available. There are four tiers, each with two dipoles per panel, and six panels per tier.

Yes, there does seem to be something wrapped around the stay cable on the left.

Plotting the Ofcom data shows a variation from the ideal pattern, with nulls of around 3 dB at 60 degree intervals.

Looking across to the "old" mast. Still there. Still carrying lots of services...but with a couple of changes.

Taken from the wrong position - but whilst the four pairs of phased dipoles remain the "umbrella" has gone. Once upon a time the panels at the bottom of this image were Channel 5 analogue - currently used Mux 7 (and Mux 8?)

As to the dipoles...they're at the right height to have been the original Glasgow DAB array which was in service by May 2000. What follows is speculation...

Was there a plan to clear the old structure which included a new Glasgow DAB array on the new mast? Was this plan then abandoned before FM services were moved? Did this subsequently allow SDL to "inherit" the feeder on the new structure, with the Glasgow MUX from its original array?

At 225 m the log periodic on the right (Forth FM) is a constant. The array for Clyde 1 has been simplified. Four tiers each of two crossed 3-element yagis have been replaced by six slant-polarised 3-element antennas.

Ofcom data shows a change in ERP - was 10 + 5 kW (vertical/horizontal) and now 13 + 11.5 kW - but curiously no change to the detailed parameters. Another oddity is the date given by Ofcom, February 2015 yet we understand the work was done around September/October 2014.

The opportunity has been taken to recover the SHF dish.

Can't identify the exact type of antenna - the "pod" over the feed point may be a clue to the manufacturer.

(Some of the metalwork associated with the previous array seems to have been left in place?)

Black Hill index

Kirk o'Shotts

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