Tuesday, February 14, 2017

The Radio Scene in Madras-Chennai

Three weeks back, we presented Part 1 in a mini-series of topics on the radio scene in Madras-Chennai with particular reference to the inroads of the recent disastrous Cyclone Vardah. This brief topical series was researched and written by Jose Jacob VU2JOS in Hyderabad India and it includes information that was gleaned during a visit he made to the station a few years earlier.  Last time in Part 1 here in Wavescan, we presented the story of the shortwave station at the three part transmitter complex at Avadi where one of the antenna systems was felled by the high winds of the recent cyclone.
            In our program today, we present the story of the two other stations located at this three part transmitter complex in Avadi.  The shortwave station is the first that you will encounter as you enter this large radio complex, and in our program today we move on to Transmitter Building No. Two. 

     Avadi Transmitter Complex: Building  - Mediumwave
            As Jose Jacob reports: A second transmitter building is about half a mile away from the shortwave building.  In this building there are two 10 kW BEL HMB163 medium wave transmitters which were commissioned on October 14, 1994.  These two units operate on 783 kHz with Vividh Bharati programming on a down link satellite relay from Mumbai-Bombay. 
            Next to these two 10 kW transmitters is a 20 kW Harris DX20 medium wave transmitter operating on 1017 kHz with B channel programs from the AIR studios in Madras-Channai.  This third transmitter at this second station at Avadi was commissioned on October 17, 2001.  Back in 2001, a mobile BEL 10 kW transmitter was in use here temporarily while the Harris transmitter was under installation.
            Interestingly the signals from these transmitters that are assigned the two frequencies 783 kHz and 1017 kHz are diplexed into the same self radiating mast antenna at a height of 300 feet.  Up until 2001, an NEC MB124C was in use here on 1395 kHz as the AIR B Channel, and this unit was moved to the A channel building complex to be used as a standby for the main transmitter.  There are also standby generators in this building.

     Avadi Transmitter Complex: Building - Medium Wave
            Less than a quarter mile away from Building Two, is the third building, in which the original transmitter, a 20 kW BBC SM42A3 mediumwave unit, was commissioned on January 11, 1956.   At first it used to operate on 940 kHz but shortly afterwards it was changed to the present channel of 720 kHz. This transmitter was dismantled in the mid 1990's. 
            Currently in this building, there are two medium wave transmitters at 100 kW each, both BEL model HMB140 operating on 720 kHz.  This double set of transmitters replaced the earlier 20 kW BBC medium wave transmitter that was commissioned thirty one years earlier.
            There is also a 10 kW NEC MB124C transmitter here in Building 3 that is in use as a standby unit.  It was previously in use in Building 2 for a period of seven years and it was transferred to its new location in 2001.  There is a standby generator for this 10 kW NEC transmitter, too
Avadi Transmitter Complex
            Because the Avadi transmitter site is near the coast of the Bay of Bengal, they use directional antennas to beam their programming within the Indian mainland.  For this reason, the main self radiating tower is 485 feet tall with a nearby reflector tower 400 feet tall.  
            Programming on five channels from the AIR studios in suburban Mylapore is received by a studio to transmitter link on 1440 MHz, though some programs are also received by satellite. The original Mylapore studios were inaugurated on April 13, 1969.
            In the entire three station site, says Jose Jacob, "I could see more than 15 towers. Several cows were grazing under the antennas, maybe to bring down the grass.  The staff uses Motorola walkie talkies throughout the site". 
            At the time of my visit in 2004, the security personnel and others were seen using transistor radios and wired speakers and they were listening to their station keenly while it was giving the results of the Indian General Elections.
(AWR-Wavescan/NWS 415)