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There is one 70cm UHF repeater located on this site.
Permanently linked directly to VK7RAA on Mount Barrow & indirectly to VK7RCH and VK7RML.
In 1976, Tasmania's second amateur repeater station on 2 metres was installed at the summit of Mount Wellington on the old ABC Tower (now decommissioned) by the Southern Branch division of the VK7WIA club.
The repeater ran 75 watts from a antenna height of 70 metres AGL. Over time the repeater eventually was removed from service due to a number of factors.
Photo Credit: VK7RR
Mount Wellington is a strategically placed mountain in that it has line of sight to just about all of the Hobart area and is the highest peak in populated Southern region. With that comes problems.
1) The mountain is the main FM broadcasting and television transmitter site. Several transmitters run kW's of power to high gain antennas causing intermod and noise on some amateur bands.
2) Access to existing facilities. It is not possible to setup a new facility on the mountain, as it is governed by a special set of decrees whereby only certain developments are allowed. Therefore access needed to be obtained to the existing transmitter facilities.
3) Winter. The Roaring Forties are strong westerly winds found in the Southern Hemisphere, generally between the latitudes of 40 and 50 degrees. Mt.Wellington being the highest peak in the region, regularly experiences icy winds at the summit, which have been recorded at sustained speeds of over 157 kilometres per hour (98 mph), with rare gusts of up to 200 kilometres per hour (120 mph). In the winter it often snows and the mountain is often snowcapped. Lighter snowfalls in spring, summer and autumn are also common. A day on the summit can consist of clear sunny skies, then rain, then snow, then icy winds and then clear again.
In early 2013, I, VK7HH (the author) set about to re-establish an amateur repeater station back on top of Mt.Wellington. Of the three key problems, (2) needed to be addressed first.
Access was granted by one of the owners of the transmitter facilities. This came with strict guidelines and procedures, as it is a commercial site, which we were more than happy to, and continue to abide by.
(1) was then the next challenge to face. Testing on the preferred band of 70cm proved reliable, and the repeater was installed in early 2014. 2m was tested for a short time for viability, however unknown interference and desense occurred. The repeater when transmitting would have in excess of 30dB+ desense in addition to a effective sensitivity reduction of 10dB. On rainy or days with increased moisture on the site, these issues disappeared. I have two theories what the cause was.
(a) The whole roof of the building that the repeater is housed in, is covered by a galvanized steel grating to break up ice fall off the tower. The close proximity to this, coupled with the fact that the grating is installed in sections and not bonded together creates little diodes when "lit up" with RF from the amateur transmitter and(or) broadcast transmitters, therefore creating desense/intermod.
(b) The tower has had a couple of coats of paint over the years, however exposed portions of the tower (including the antenna) have rusted, again causing the "intermod diode" issue. This theory is less likely as the amateur repeaters antenna is physically located further away from these portions of the tower, therefore increasing isolation between sources.
Challenge (3) required anything external to the building to be rugged for protection from the wind, ice and snow and positioned to minimize damage from ice fall off the tower.
Thus far, (3) has largely been a success as there has been no damage externally to the antenna from ice fall.
Voice ID's are done internally and also kindly provided by John Blackman
APRS Digipeater: PRM8030 with TNC-X (XDigi board) running v3.0 firmware.
http://http://aprs.fi/info/a/VK7RTC
Antennas:
- 1 x SMD for 70cm repeater (soon to be upgraded to a 4 dipole stack)
- 1 x SMD for link to Mount Barrow
- 1 x SMD for APRS
As I do not have a photo of the current antenna setup, below is an older photo. The black vertical has been replaced with a single SMD and the bottom split dipole removed as it was used for testing purposes.
Photo Credit: VK7FMRS