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VK7RTC Coverage plots

27 October, 2015 - Reading time: 5 minutes

Further to my blog post yesterday, I showed the example of the Southern Outlet as a fringe area of coverage from VK7RTC.

On Mt.Wellington there are two "sites". We can call them the North and South site. VK7RTC is located on the Northern site. As such it has excellent coverage out that way, unimpeded.

Below is a site view towards the South (Kingston/Southern Outlet direction). As you can see, there is a car park, and a fair bit of rock.


Let's look at the view on the other side of the trig point courtesy of Google Street View. A line of sight view towards Kingston and the outlet!

Now... what would happen theoretically if the repeater was located on the other side of the mountain? What would coverage be like? Let's compare.... another Splat! plot....

Interesting.... a lot more yellow... lower path loss, a lot more line-of-sight in this area. Of course the Southern site then presents the problem that it is not ideally suited to the North anymore... the carpark and half of the Pinnacle is once again in the way... and it cannot be put in the middle (i.e. trig point).

So just for fun, how high does the antenna need to go on the Northern site to get near similar path loss results in Splat!, hopefully resulting in real world results? Both tests were done with antenna heights of 4 metres for the repeater (which is roughly what it is now without measuring), and 1.5m for a typical mobile.

The height difference between the Pinnacle (trig point) of Mt.Wellington and the current repeater location is apparently 7 metres according to Google Earth. I'm a bit doubtful of this as the summit is 1271m ASL and GE reports it as 1263m? Anyhow... Let's try 10m antenna height...

Original 4m Antenna Height "Southern Site"                                                        

10m Height

 As we can see a fair bit of improvement, especially around Kingston area to the bottom of the plot. Let's try 15m now.

15m Antenna Height                                                           


A little bit more improvement. This would probably be sufficient enough to provide reasonable coverage as there is a lot more signal getting down into the Kingston area, so there may be more chance of reflections back up the "valley" on the Outlet.

The next question.... is it possible to get the antenna that high? The tower is off limits for antennas, so that rules that out, and theoretically if we go by the HCC regulations, or the Building Regulations of 2014 of antenna heights, the following is exempt from the requirement for a building permit:

(e) a non-roofed windmill, a mast, antenna or flagpole or the support structure of a wind turbine if –

(i) it is not attached to a building and not more than 6 metres high; or

(ii) it is attached to a building and is not higher than 6 metres above the topmost point of attachment to the building

VK7RTC's antenna is attached to the building and is currently 1.5m above the topmost POA. Therefore we could extend it, possibly. However other factors such as the weather, safety, and the fact the area around the Pinnacle is under special regulations may make it difficult for us to do.

We shall see. In any case, if someone says "I'm noisy......... but I can SEE the mountain".... they have been educated as to one of the potential reasons why they are noisy....