Restoring My Trident-GP Antenna: A Journey in Preservation

Untold Story: Experiments and Entertaining Intercepts!

Restoring my Trident-GP antenna went beyond a simple project; it became a journey blending preservation with innovation. This antenna holds a special place among ham radio enthusiasts, revered not just for its functionality but also for its iconic design and community significance.

Years ago when I was relocating to a new city, the cradle housing the antenna's radiating elements suffered damage, prompting an extensive restoration effort. Constructed from cast iron, conventional welding methods were impractical. I sought advice from numerous fellow hams to find a solution.

The Challenge

The broken cradle of my Trident-GP antenna became a major hurdle. Made of cast iron, it

couldn’t be fixed using conventional welding methods. Suggestions poured in from other hams, with some recommending Araldite. However, Araldite wasn’t suitable for cast iron and could potentially disrupt the current flow. Metal paste seemed like a viable option, but it was either unavailable locally or prohibitively expensive to source online, particularly from international vendors.

Failed Attempts and Frustration

I considered fabricating a new cradle, but the unique conical shape of the poles, where two radials thread in, made it a complex task even for skilled blacksmiths. A blacksmith I consulted offered to try gas welding but couldn’t guarantee success, warning of potential damage to the cradle. This dilemma significantly impacted the VSWR (Voltage Standing Wave Ratio), making it crucial to find a precise solution.

A Breakthrough

After much brainstorming and persistent effort, I managed to mend the broken cradle using a

combination of M-Seal, Fevikwik, copper braid strands, aluminum, and a thin layer of Araldite. This process required meticulous work, but the end result was a robust repair that has weathered well. The sense of accomplishment was immense as I successfully weatherproofed my two-decade-old Senao SN-258 Trident-GP antenna, known for its vibrant design and exceptional performance.

The Repair Process

For additional support, I used a transparent three-element isolator cut to size. The original 50-ohm coax cable that came with the antenna was of superior quality, and the PL259 plug

remained in excellent condition. Instead of electroplating, I added colorful heat shrinks to weatherproof the antenna further, likely making me one of the first to use such a creative approach. Testing the antenna post-repair yielded satisfactory results, reaffirming its remarkable design and radiating pattern, which set it apart from other ground plane varieties.

Unique Performance

Manufactured by the esteemed Taiwanese telecom firm Senao, the Trident-GP antenna boasts six copper ground plane radials of alternate lengths, unlike the inferior Chinese versions with fewer radials. I achieved an impressive communication range of 26-30 kilometers, vividly recalling seamless semi-duplex conference mode communications using two Senao SN-258 handsets alongside the Base Station. Sporting a sleek design the Senao Trident-GP outshines its Chinese counterparts, which typically feature a broader cradle with only three ground plane radials.

Having said so, I do not mean to undermine China's prowess in manufacturing high-quality products at competitive prices, a fact relied upon by several countries worldwide. The core problem lies within our system, where there are no quality control checks for goods arriving in India, compounded by unscrupulous importers intentionally importing substandard goods to seek larger profit margins, and the prevalence of bribes and corruption. Unlike India, the USA's FCC ensures stringent quality control for imports, guaranteeing citizens receive quality products. Additionally, China faces challenges from its own illegal manufacturing, which the government is constantly trying to control.

Personal Significance

This high-power, long-range cordless phone proved invaluable when my mother suffered a cerebral attack. It provided convenient monitoring of her condition and the attending home nurse during the day while my sibling and I were away at our respective offices. It was indeed like a hotline and it saved us significantly on mobile call expenses during the costly call rate era of the 2000s.

Importantly, the equipment's signals never interfered with frequencies used by law enforcement and security agencies. During better times, my mother joined me in various range testing experiments. I also connected our two-way wired wall-mounted intercom phones to the base station. One intercom set was placed in the drawing room, another in the kitchen, and the base station in the bedroom. It was fascinating to make direct calls between handsets, the base station, and the intercom phones, even hosting conference calls in simplex mode with both handsets and in half-duplex mode with the intercom phones.

Today, this antenna continues to perform flawlessly across VHF/UHF ham radio frequencies, embodying reliability and functionality in our cherished hobby.

Historical Context

Mobile phones debuted in India in July 1995, with the inaugural call made by then Union Telecom Minister Sukh Ram to West Bengal Chief Minister Jyoti Basu during a public event in Delhi. This event marked a significant milestone in India’s telecommunications history, transitioning from dominance by landline phones. The first mobile services were launched by Modi Telstra, a joint venture between India’s Modi Group and Australia’s Telstra, in Kolkata using AMPS (Advanced Mobile Phone System) technology. Although initially limited in scope, this launch set the stage for the rapid expansion of mobile telephony across India in subsequent years.

Long before mobile services reached northeast India, many people carried handsets

resembling designs from Nokia, Motorola, Siemens, and Ericsson of that era. These devices featured distinctive long 7-stage telescopic antennas that needed to be extended for communication. Owners typically installed Trident-GP antennas on their rooftops and terraces, making them easily identifiable. These devices were actually long-distance, high-power cordless phones capable of operating efficiently within a radius of 15 to 18 kilometers. Connecting a regular landline phone to their base station allowed users to make phone calls while on the move, serving as an alternative to mobile phones at the time.

Discoveries and Insights

In 1998, my friend Parambir Singh Sehdave from Shillong acquired a long-distance cordless phone from the grey market at a steep price. He installed the antenna atop his building and connected it to his landline phone. It was during this time that I had the opportunity to see and experience the entire setup first hand. We conducted range tests from various locations, concluding at my residence where we made successful calls. I was thoroughly impressed! Parambir's handset resembled a Motorola, but upon closer inspection, it was branded 'Motorcycle' in a style reminiscent of Motorola. He also introduced me to a neighbour who owned a similar cordless phone, installed with an antenna atop the former Dream Land cinema hall.

Over time, my curiosity grew as I noticed these antennas on various rooftops and terraces, including those at the Superintendent of Police's office premises and the homes of state ministers. I was keen to learn about the frequencies these cordless phones operated on, but the brochures that came with the sets did not provide this information. Back then, with no access to YouTube or the internet, finding detailed technical specifications was a challenge.

Airwave Revelations: Entertaining Intercepts

One rainy day, while confined to home, I grabbed my portable world receiver radio and lay in bed, scanning the VHF/FM bands. In those days, northeast India had no commercial FM stations, so the FM band was mostly quiet except for mornings and evenings when All India Radio's (AIR) Shillong studio connected to its North Eastern Service's shortwave transmitting tower at Laitkor hills. Occasionally, I'd catch transmissions from my homemade low-power clandestine FM radio station playing Western melodies. AIR's low-power VHF micro link on the FM band offered remarkably high audio quality compared to stations on AM and shortwave bands. 

Twisting the tuning knob, I stumbled upon an intriguing conversation between a couple that seemed to go on forever. They were discussing quite personal matters, punctuated by giggles and laughter. Just a hair's breadth away from this broadcast, I distinctly heard the clear sound of a phone ringing. After a brief pause, someone answered the call, and to my surprise, it was a minister. With a unique blend of style and authority in his voice, he confidently asked the attendant, "Do you know where I'm calling from? I'm in my car! How's the reception?" The attendant, sounding flustered, replied, "Sir, okay sir, thank you…"

The next afternoon, I once again grabbed my world receiver and slowly scanned the bands for the faintest signals. To my surprise, I stumbled upon a crystal-clear conversation between a couple. The woman's voice rang out loudly, possibly in a cranky mood, as she lectured and scolded the man—who I assumed was her husband. He tried desperately to calm her down, practically begging her not to speak so harshly, explaining that their conversation over the cordless phone could be heard by others on the FM band, making him look bad. Despite his pleas, the woman continued to shout even louder. Their dialogue was a mix of Khasi with occasional punchy English phrases.

Another hilarious conversation I bumped into the airwaves was in the evening. The conversation was long enough but here are the essential part that I remember. What I guessed

it was a call just between the handset and the base station. The man after completing his essential marketing such as vegetables, fish, etc and then made a direct intercom call from his handset to the base station at his residence to speak to his wife if anything else were required. The couples sounded very excited while the lady said to comeback quickly and the man concluded saying he would be back home shortly after getting a ‘half’ from the wine store. They were Bengali couples!

Continuously monitoring the VHF/FM band provided me with endless entertainment, intercepting various phone conversations. One evening around 8:00 PM, I caught a clear signal of a man speaking loudly and aggressively, accusing someone on the line in Hindi with a distinctive local accent, seemingly under the influence of alcohol. His tirade was peppered with expletives, directed at someone of a minority religion. The other person remained mostly silent, responding occasionally with "ji Sir, ji Sir" (yes Sir, yes Sir).

Shocked by what I heard, I decided to record the conversation for proof. The voice sounded familiar, and I had a strong suspicion about the location. Convinced of my findings, the next morning I headed straight to the Superintendent of Police's office, where I was welcomed due to my role as a journalist. After exchanging pleasantries and a cup of coffee, I broached the topic directly.

"Sir, I noticed a prominent antenna on your office rooftop. Is the police authorised to use long-distance, high-power cordless phones that operate on potentially illegal frequencies?" I asked.

The SP's demeanour shifted slightly, and he replied, "We do use such cordless phones, but it's not for the Meghalaya Police to determine legality. That's for the Department of Telecommunications (DoT) to decide."

Curious, I pressed further, "What about other government officials and the public using similar cordless phones?"

He responded with a knowing smile, "You might want to inquire with the DoT about that."

Leaving the SP's office, I knew I had a potential exclusive story in hand. However, I decided to hold off on reporting until I could gather more information.

During that same weekend evening, I once again tuned into my world receiver, eager for more

entertainment by intercepting phone conversations on the airwaves. The FM band was buzzing with multiple conversations across various frequencies, some overlapping and others distinct. Amidst the chatter, I recognised a familiar voice unmistakably—none other than our friend, Parambir Singh Sehdave. He was at the Shillong Club with a relative from Mumbai, engaged in a game of billiards as I gathered from his lively exchanges with family members during my first interception.

After the first call ended and the receiver remained tuned, I didn't have to wait long. Within minutes, another call came through, and Parambir answered, later passing the handset to his visiting relative for an STD call from Mumbai. I couldn't resist recording this exchange for amusement. Later, I dialled Parambir from our landline and played back the recorded conversation from my cassette. His reaction was priceless—I could almost sense his concern about the privacy of using such sophisticated long-range cordless phones, which offered a taste of mobile phone convenience years ahead of its time in Meghalaya and Northeast India, eliciting awe from peers.

Long Distance Cordless Phones: My Journey

Through my thorough experiments and exploration into these Chinese-made long-distance phones, I gained significant insights. I became convinced that despite the various designs from different manufacturers, the fundamental system architecture of these devices was essentially the same — all of them transmitted signals that could be easily intercepted on FM commercial frequencies, posing a risk to the privacy of phone conversations.

These devices typically cost between INR 15,000 to over INR 28,000, which was quite exorbitant for that era. Beyond their utility, owning one also became a style statement. Consequently, people across Northeast India and several other states in India clandestinely acquired these cordless phones.

My interest in owning a set like this grew, but I wanted one where the signals wouldn’t

broadcast on commercial FM frequencies to ensure privacy. After some research, I discovered that such devices could be obtained at a very cheap price in Tamu, a border town in Myanmar near Moreh town of Manipur. So, my sibling and I headed there and found the perfect set. The handset was an exact replica of the Siemens S-4 model from that era and worked flawlessly. However, nearly a year later, the handset developed a problem that no mobile repair shop could fix.

A couple of years later, I had a work-related trip to Kohima and Imphal and decided to travel by road. As I passed through several towns, I noticed the Trident-GP antenna on residential bungalows and commercial buildings. Upon reaching Imphal, a good friend took me to a repair shop where my faulty handset was fixed right away. Then, he introduced me to a trader specialising in long-distance cordless phones. There, I discovered the Senao SN-258 with double handsets, a base station, and an antenna. It was an irresistible deal, and I bought it on the spot.

Experiments and Adventures

I conducted several experiments with the range of my new device. I even rigged a mag-mount antenna on our car's roof, placed the base station inside the car, and powered it through the cigarette lighter port, as the base station required 12 volts DC. With everything set up, our family, including our furry four-legged pet, would often take long drives to offbeat locales during weekends or holidays, enjoying nature's beauty and winter sunlight. The experiments continued with range tests, handset-to-handset communication, and half-duplex conference mode using the base station in speaker mode. It was great fun and unknowingly nudged me towards amateur radio.

Conclusion 

I took on the task of restoring my more than two-decades-old Senao SN258 Trident-GP antenna's cradle, which had broken down. With patience and persistence, I not only managed to restore it myself but also weatherproofed it in an unconventional way using colourful heat shrink tubes, giving it a unique and enhanced aesthetic. While documenting the various stages of the restoration process with photographs, a flood of memories related to my quest for long-distance cordless phones came back to me. These memories, etched deeply in my mind, inspired me to share this story in this article. Reflecting on the entire journey has been uniquely fun and fulfilling.

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