I’ve read through the antenna documentation at work for the Artarmon Commercial FM antenna & spoken to our Engineer about it, & can give these following details.
Gore Hill may differ slightly to Artarmon, but I don’t have access to any technical documents about it, it’s possible it might be a bit more OD, & I’m not sure on the direction of the antenna or tower faces at Gore Hill?
Artarmon is a 4 sided, 6 bay (levels), panel (24 panel total), Right Hand Circular, VHF Band 2 88-108MHz array.
It’s an unequal power split, phased directional array with a 4:4:1:1 power split, which means 2 faces have 4 times the power of the other 2 faces going into the elements (not resultant ERP power levels which will differ because of the element, panel & face phasing).
The 4 faces are named A, B, C, D, with face A centred at 63 degrees from True North, physically face B is at 90 degrees to face A & so on around the tower, electrically their relative phase is different to their physical.
Power splits are face A-1, B-1, C-4, D-4.
Horizontal & Vertical polarisation radiation patterns differ, but for ease of understanding (hopefully), I’ll indicate rough power levels for the horizontal pattern, as if you were standing on top of the tower looking down over the antenna.
Using True North as the 0 degree start point, there’s a notch about 9 degrees which is -8 dB from full power, this comes out with a lobe at about 27 degrees which is around -5dB from full power, this lobe reduces down to another notch at approx 63 degrees (flat on face A) around -12dB from full power, there’s another lobe at 105 degrees which is around -6dB from full power, this goes down to another notch at 135 degrees falling to about -12dB from full power, this goes out to another lobe at around 187 degrees which is -6dB down from full power, there’s another notch at about 208 degrees which is around -8dB from full power, we then go out to the main power lobes first one at 230 degrees, (just off physical centre of face C) which is around -0.9dB down from full power, this comes in to a deep 2 degree wide notch at 275 degrees which is about -7dB down from full power, then there’s another main power lobe at about 293 degrees which is about -0.9dB from full power, there’s another small notch at about 315 degrees which is around -3dB from full power then we go out the the last main power lobe at 340 degrees which is about -0.9dB from full power.
Full power is 150kW ERP, sorry I can’t be more accurate & it’s detailed what I’ve said, but hopefully you can understand or make out the pattern, as you can probably tell/make out, to achieve the deep notches (essentially North & South), but more so the deep 2 degree notch at 275 degrees, at no point in the horizontal radiation pattern does the Artarmon Commercial FM antenna array push out full power at 150kW.
I don’t have the time right now, but if someone wants to do the calculations & work out what power levels are actually (roughly) pushed out in what directions, you’re welcome to do it & post back here, they will roughly meet the licence specs listed by ACMA, taking into account no point reaches full 150kW, so all points will be a -?kW figure.