Nautel & Radio Veritas Bring the Good News
Radio Veritas is no stranger to the South African broadcast landscape. Having started its operations in 1999, the radio station had to initially be content with running its broadcasts on a short-term basis on FM frequencies in the Johannesburg area. Considering that a potential Catholic audience of 3,500,000 could be targeted in South Africa, a longer term (and permanent) broadcast platform was sought to establish a permanent, easily accessible and identifiable location on the radio dial. Given the scarcity of FM frequencies in the metro areas, the station considered options for broadcasting on medium wave.
The use of high power medium facilities in South Africa has dwindled to a handful of operating stations, largely through the migration of commercial stations onto FM frequencies. It was imperative that Radio Veritas target a frequency that was available at an operational facility, as building a brand new station would be prohibitively expensive and uneconomical for a single high power medium wave frequency.
As the story goes, the South African Broadcasting Corporation (SABC), requested its service provider, Sentech, to switch off its Radio Metro transmitter on 576 kHz (at Sentech Meyerton Transmitting Station) along with relinquishing the frequency in June 2011, as this station has completely migrated to FM. This opened up an opportunity for Radio Veritas to lodge its application with the Independent Communications Authority of South Africa (ICASA) for this frequency, with a transmitter power output (TPO) of 50 kW.
The Meyerton medium wave transmitter site was built in the early 1980’s for a single MW frequency. The “state-of-the-art” transmitters purchased at that time were comprised of a parallel combination of two 50 kW Marconi B6034 transmitters, producing 100 kW TPO. This was fed into a TCI monopole antenna, of 286m height. In the early 1990’s, it was decided that the two Marconi transmitters could be ‘split’ and be operated as single equipment, along with the addition of a transmitter Diplexing unit. This was to enable the addition of a second channel at the site, namely 657 kHz for Radio Pulpit. In late 2008, the 657 kHz transmitter was replaced with a solid-state transmitter, supplied by Thomson.
The application for 576 kHz was duly considered by the ICASA which granted Radio Veritas its license for 576 kHz in September 2011. Radio Veritas was informed by Sentech, that the Marconi 576 kHz transmitter had reached the end of its useful life and that replacement was mandated. Radio Veritas embarked on a closed tendering process for the purchase of a new transmitter, and after short listing its preferred suppliers, chose the NX50 from Nautel, on the basis of technical compliance with its specifications, along with guaranteed delivery and price competitiveness of the offering. An order was placed on Nautel, which indicated the transmitter would be ready for factory acceptance testing (FAT), on 6 February 2012.
As the transmitter was to be installed on a Sentech-operated transmitter facility, Radio Veritas commissioned the services of Broadcom International (under Chris Joubert) to remove the old Marconi transmitter and then install the Nautel transmitter into the facility. It was decided that Sentech’s Dave Berndt and Chris Joubert attend the FAT of the transmitter in Canada, along with Vaughan Taylor, the Southern African representative for Nautel.
Nautel arranged to have the NX50 shipped via air to Johannesburg, from where it would be transported via road to the Meyerton MW transmitter facility. Chris Joubert removed the old Marconi 576kHz transmitter, to create the necessary space in the transmitter hall for the Nautel, which arrived in early March.
Part of the installation requirement was to remove the Marconi paralleling and switching cabinet, which became redundant with the removal of the two single tube transmitters. This was replaced with an RF U-Link panel which was supplied by Sentech. This permits either transmitter to be routed to its respective antenna diplexer input port, or to be connected to a dummy load for testing purposes. Both transmitters are interlocked into the U-Link frame for safety of personnel. This, along with the installation of the NX50, was expertly completed by Broadcom.
The existing Programme Input Equipment (PIE) infrastructure was retained, though a new Orban Optimod AM 9400 and audio silence sensor was supplied by Radio Veritas for the installation. The primary audio feed is delivered to the site via a V.35 circuit which terminates at the adjacent site. A short STL hop provides the audio to the MW transmitter site. It was a considered objective to have the transmitter’s Advanced User Interface (AUI) available remotely – For this purpose, Sentech saw to the installation of a VSTAR Internet™ connection via VSAT, as no Internet Access on site was available.
During the installation of the transmitter, it was discovered that it had sustained ‘concealed damage’ internally during transportation from the factory to its final destination. The factory was duly notified and offered remedial action, which saw the original warranty period being extended to cover any eventualities that could arise from the damage.
The transmitter was switched on into the on-site dummy load and demonstrated full compliance with the suite of tests that Chris Joubert from Broadcom used on it. On completion of the tests the transmitter was switched into the antenna, and test broadcasts commenced from 29 March 2012, a week ahead of scheduled on-air date being Easter Sunday (on April 8, 2012).
The AUI of the transmitter has been extremely useful in gathering data on the operation of the transmitter, particularly through a thunderstorm. The built-in protection mechanisms of the NX50 ensured the transmitter’s survival during recent lightning and thunderstorm activity. The Highveld region of South Africa where the MW station is located is subject to some of the worst lightning activity in the world, and hence requires attention to its effective mitigation on a transmitter site.
The NX50 achieves an overall efficiency of 88%, which sure is good news considering the old tube based Marconi transmitters achieved 50%, at best. To further conserve power consumption, the Amplitude Modulation Companding (AMC) algorithm is being used to dynamically vary the overall carrier power in sympathy with the audio modulation. The combined efficiency along with the use of AMC will indeed be a blessing to Radio Veritas in terms of the transmitter power consumption and electrical bills.
Says Fr Emil, “I am more than impressed with the quality of this NX50! I am really happy that we decided on the Nautel and I can’t believe how small the NX50 is compared to what was there before. Technology is really wonderful.”
Fr Emil Blaser, OP
Director, Radio Veritas
Johannesburg, South Africa
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