Monday, February 18, 2013


Mandarmoni DX pedition IV
We were again drawn towards Mandarmani. This sea beach resort 180 km away from Kolkata has a long stretch of beach some 6 km and the sea side resorts still run on gensets because there is no running electricity. Memories of our past DXpeds such as Diego Garcia 4219 kHz blaring in our ears was enough to motivate Alokesh Gupta the chief motivator of this DXped to make a journey all the way from New Delhi some 1600 km away. Along with Alokesh was also C.K.Raman (VU3DJQ) from Delhi who has an uncanny knack of zeroing on the part of the radio dial where an exotic station is sure to be found. From nearby Kolkata there were three of us Babul Gupta, Sudipta Ghose and I. We missed three veteran DXers Jyoti P Chakrabarty, Jose Jacob and Tripti Ranjan Basu. Jyoti was hoping till the last day that he could overcome his unwell health and catch up for the last part of the DXped but that would not be. Jose was called back for work at the last moment by his office. Commitments back home held back Tripti Ranjan Basu.
Like the thrill of all DXped there were obstacles on the way. The notorious North Indian fog delayed by five hours the Rajdhani express in which Alokesh and Raman were travelling and it was a pity that we could not travel together from Kolkata. A charm of DXped is the DX tete e tete, you may also call it the proverbial "Bengali Adda ", while travelling to the site. The advance party SUV with the Kolkata DXers carried the antenna stringing material and most of the receivers. Alokesh and DJQ could not even make it for the last train link to Digha from Howrah and had to catch a taxi all the way to Mandarmani.

Idea of Beverage Masts
On the way we came across a big store selling iron building materials by the roadside and Babul Gupta decided to stop to look for antenna support. What we sourced turned out to be great for DXped beverages. We picked cut pieces of building rods made of iron some 30 mm in dia and approximately 60 cm long. These were latter hammered on to the soft seaside soil to form foundation for the PVC pipes which were just positioned as sleeves over the buried iron rods. We were already carrying PVC pipes from Kolkata complete with clamp on top to secure the antenna wire. In past we had to dig to bury the PVC pipe in the ground but the foundation was never strong. The iron rods made the take easier. We reached Mandarmoni by 3 pm just after the high tide had receded and cleared the beach roads .The first thing we did on arriving at Mandarmoni was to set up the beverage support with iron rods and PVS pipes and then string a 260 m ( North east ) antenna from multi strand copper wire sourced from the army disposal stores. We set up yet another antenna some 150 m over causurina trees by the sea side in the south east direction.
Antenna splitter and Baluns
We had fashioned a decent antenna splitter this time out of a chip sourced by Jyoti P Chakrabarti and fashioned by Babul Gupta and Sudipto Ghosh. It could support eight receiver from one antenna. This splitter was put into use and cut out the use of alligator clips to tap signal from the beverage to various receivers. It functioned reasonably well. We connected the beverage to 9:1 transformer and fed in through RG58 coax. We had elaborate testing of various homebrew baluns and finally settled on one brewed by DJQ. But as we see later these were not enough to cut out the noise.

Warming up
Once we fired up the shack the South Asians started pouring in. All the Burmese station in the MW led by 594 kHz were coming in with 576, 729 and 639 kHz in tow . AIR Port Blair on 4760 kHz was throwing in moderate to strong signals. We could log all the AIR MW in the direction of East West starting from AIR Dibrugarh at one end to AIR Jodhpur at the other end. The Afro opening was fair with TWR Manzini ,
SW Radio Africa coming in. Later the Australian regional’s on 2135 and 4835 kHz were coming through. Early morning CK Raman caught a few Brazilians an the star of our last meet Radio Tarma , Peru on 4765 kHz early in the morning.

Bengal Pirates, Long Wave Beacons and greetings on the amateur net
In the morning the Bengal Pirates from Bay of Bengal came in loud and clear with their " Jatra " style programming. By now we have got used these transmissions as regular fixtures. Alokesh stumbled on the long wave Beacons and there were quite a few. In early morning as we were tuning into local amateur band net on 7145 kHz LSB, we heard VU2DPI greeting our DXped all the success.
Shack on Battery only
We had genset running in our resort only upto midnight. After that we had to rely on batteries to power the sets. The IComs and the Drakes were running very well on the battery. For the software support the laptops were there to last for some time. Mobile computing came in for the first time in this meet and I was reading off my AOKI list solely from my android phone. We were carrying three batteries but thought that the batteries would last us for the whole of four days without charging. That did not happen and on the fourth night we were struggling with power supply.

Almost lost the battle against noise.
Like the proverbial blizzard wiping out an entire expedition team after the first night we started losing it out to radio noise of the man made RFI type. This perplexed us because here we were far from any electrical activity so where will the noise be coming from ? On the first night there was thick fog from late night and by early morning droplets of water had precipitated all along our antenna. We wonder whether these droplets were the cause because the noise definitely increased as the night progressed and was at its peak early in the morning. On day two we thought that the multi stranded copper wire of our longest beverage was pulling in more noise because of its multiple joints. We replaced the whole of it with single stranded copper wire. We also installed the 9:1` balun but the second night we still had to battle noise. On the third day we set up yet another beverage directed north south and terminated it with ground via resistors. But that too did not break the noise problem. We were still bugged by noise as the night progressed and as the fog increased.

The breakthrough in our battle !!!
On the last day of our dxped we were desperate to try out something different. That is because we were simply frustrated with electrical noise. Our multi stranded beverage ( North South ) was not performing well. Babul Gupta was always pushing for something different than the standard beverage antenna for DXpeds. So we pulled it down and converted it into a huge loop by taking it round the big water body around which our resort was built. These were connected to two ends of RG 58 coax and fed into the receivers. That was the breakthrough. The first sign of our success appeared when on preliminary testing we found Myanmar on MW on 594 kHz in the peak of afternoon. It was blaring with strong signals at a time when even the local AIR station such Kolkata A and Cuttack normally have difficulty in transmitting upto this place. The noise in the bands had just disappeared and did not appear even till late in the evening. The other beverages out there were however were still picking up noise. As the night progressed, we started tasting our success. In the 25 mb there were a host of Brazilians and Argentinians. The Caribbean Beacon on 11775 kHz at 2113 UTC was sweet taste of success. Papua New Guniea Wantok Light radio on 7235 kHz came in briefly at 2110 UTC. On 4750 Khz RRI Makassar was coming in moderate to strong signals at 2130 UTC. It was all through the great loop.

Winding Up
As we were winding up the great loop antenna, we were convinced that in our next DXpeds we should try different antenna rather than the traditional beverage. The simple reason is that man made RFI is becoming so overwhelming, we need to have most of our antenna skills directed against it till we come out with the best antenna for DXpeds. On the way back home, the whole DXped team crossed the grand gates put up for the Mandarmani Beach festival. The beach festival was on the same dates as our DXped. It was meant to popularise Mandarmani as a tourist destination. But for us it meant more popularity, more tourists, more electrical noise.

Dr Supratik Sanatani  (VU3IFB)







Dr.Supratik Sanatani, VU3IFB

The super cyclone of October 1999 brought down the antenna 120 m mast of Kolkata A 657 Khz which radiated 2x 100 kw. In the words of an engineer manning the transmitter " we got a phone call that AIR Kolkata A was not audible. When we looked out, the main antenna mast simply was not there !! "The huge mast built of thick gauge metal can still be seen lying in the premises. Portions have been sawed off to make way to the newly installed 120 m mast. This incident caused disruption of Kolkata A transmissions for few days. Transmission resumed only when a new mast was put up.

The new main radiating mast of Kolkata A had a parasitic mast put up few meters down south. It was to act as a reflector and direct most of the radio signals to the north which is the populated part of the State. The southern parasitic mast was to avoid valuable signals getting lost in the Bay of Bengal to the south which is sparsely populated anyway. However, a controversy cropped up in 2011. During a tropical cyclone in July 2011 few fishermen who had ventured out to the sea were lost. There was hue and cry in the media that the disaster could have been avoided if the weather bulletins from AIR Kolkata could be better heard ( The AIR authorities were under pressure when news reports originating from the fishing town of Kakdwip said that Bangladesh Betar weather bulletins were better received over the Bay of Bengal (( The AIR authorities woke up and an engineer was dispatched in a coast guard vessel to measure signal strength of AIR transmissions almost 300 km deep down south in the Bay of Bengal. He found good to strong signals all throughout the test area. However, the authorities decided to disconnect the parasitic reflector mast to put the controversy to rest. The parasitic mast still stands up mournfully though in the antenna field of Chandi some 24 km south of Kolkata.

As if this was not enough, the 120 m mast of Kolkata B snapped in May 2012. This was not due to any cyclone or gale. It was presumed that one of the guy ropes anchoring the mast that snapped and that caused a disbalance. This in turn caused a cascading effect and finally the main mast snapped. AIR Kolkata B 100 kw transmitting on 1008 kHz was disrupted for almost 20 days while a new mast, somewhat shorter in height was put up. This new mast has a loading hat on top and rhombic elements on all sides. Presently this is fed by 10 kw standby brand new RIZ mobile transmitter which is running at 8 kW because one part of the panel is not working and the engineers conversant with BEL transmitters would not risk tinkering with the malfunctioning panel of Riz mobile transmitters which is in the warranty period. They would rather wait for the authorized technicians of Riz transmitters to arrive.

Pilferage is another minor irritation which bugs the antenna fields of Chandi. Even though manned by security guards round the clock,and watch towers in the periphery the precious copper of antenna and feeder elements are prey to the thieves. Most often the pilferages would be minor e.g. one coil of some hundreds of tank circuits in the antenna support wires or few lengths of concentric feeder lines. However, these would disbalance the fine tuning required for that extra last mile for the radio signal !

Yet another element which upsetting the fine tuning is the collapsed old tower which is awaiting bureaucratic clearance for disposal . A mammoth steel structure in the antenna fields is bound to add some inductance here or there and compromise design efficiency. The same applies to the disconnected parasitic antenna mast in the south which is still there completete with the ground radials. This is bound to compromise the design efficiency.

The Engineers at the site were however very upbeat. They are proud that their signals were getting around in spite of all the difficulties and they have faithful listeners tuning in. One engineer who had just completed a stint at Orissa talked about a 90 year old faithful listener who would telephone the station at the slightest fall in transmission quality. However, he would also sympathise with the ground realtites. Talking about ground realities in India, I was reminded of the Engineer at AIR Aligarh HPT who talked about Neel Gai's ( charging into antenna curtains and disrupting transmission.

Report by Dr Supratik Sanatani after a visit to Amtala and Chandi facilities of AIR Kolkata along with Babul Gupta, Sudipta Ghosh & Swopan Chakraborty in July 2012.