DON'T ALWAYS BELIEVE ChatGPT!

I had an amusing little situation happen here a few days ago. My Facebook friend, Bill Harms, has been posting examples from his excellent library of old QSL cards from an earlier era. They have been bringing back wonderful memories as well.

One of his recent posts was of a QSL from Radio Abidjan, Côte d'Ivoire (Ivory Coast). Very nice! I have the same QSL card. So, I riffled through my old cards and pulled out my QSL. I wrote a reply to Bill's Facebook post:

Despite being regularly heard via both short path (my mornings) and long path (my late afternoons), QSLing this station proved to be a real challenge for me. The first report was for 11920 kHz in December 1971. Then 7215 kHz in April 1972, and 4940 kHz in May 1976. Nothing back for any of those reports. Perhaps my French was just too awful!

Finally got the card for reception of 7215 kHz (Home Service in French) on August 22, 1983, between 0647 and 0727 UTC. This was for the late afternoon long path reception. In those days, LP West Coast Africans were a feature of winter afternoons, mostly on 60, 49 and 41mb. The LP distance to my (then) QTH in Melbourne, Australia is 24,822 km (15,423 mi).

The station used the same design QSL for years.

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To work out the Great Circle long and short path distances, I use an online resource. It came up with the distance from Abidjan to Vermont (Melbourne) for the LP reception. Cool. Nearly 25,000 km is quite a feat for a 10 kW signal. But this was not uncommon in the days of little RF man-made interference, compared to today's noisy shortwave bands. In fact, other LP signals in my late afternoons were Togo, Guinea, Mauritania, Ghana, and Senegal (amongst others). These countries were running their early morning services for their domestic shortwave audiences.

For Melbournites like myself, the winter evenings draw in early and by 0730 UTC (5:30 pm local) it was getting dark. So, a long path signal travelling in almost darkness for the entire distance, especially over large oceans (where there is less absorption of the refracted signal than over landmasses), the Africans could cover the distance remarkably well.

Click on the map for a larger view

Referring to the map above, this is the Great Circle long path that the Abidjan signal would have travelled, as calculated for 0647 UTC on August 22, 1983. The dotted red line indicates the signal would have crossed the North Atlantic Ocean, through Canada and down across the Pacific Ocean, reaching Melbourne just before sunset - a predominantly oceanic trip.

If these West African countries were still on shortwave today, would we still get this reception? Probably. But we wouldn't be listening from home, but rather in noise-free locations in the countryside or down by the coast. The only station still operating from West Africa today is Radio TV Mali, Bamako, on 5995 kHz with their morning service between 0600 and 0800 UTC. That signal is becoming increasingly more difficult to hear, even in the low-noise forests and bushland near my home.

So....What's this business about ChatGPT?

While working out the distance between Abidjan and Vermont, Melbourne with my usual resource, I wanted to see if ChatGPT would give me the same answer. Just curious! Here's how the exchange went:

ROB: What is the great circle long path distance between Abidjan, Ivory Coast and Vermont, Victoria, Australia?

ChatGPT: The great circle long path distance between Abidjan, Ivory Coast and Vermont, Victoria, Australia is approximately:

• 15,245 km

• 9,473 miles

This represents the longer arc around the Earth, as opposed to the shorter “short path” great circle route.

ROB: Incorrect! That is the short path arc. Try again.

ChatGPT: You’re absolutely right, Rob — thank you for the correction. The great circle long path distance (the longer arc around the Earth) between Abidjan, Ivory Coast and Vermont, Victoria, Australia is approximately:

• 24,822 km

• 15,423 miles

This long path route is nearly the full circumference of the Earth minus the short path, and it’s relevant in contexts like long path HF radio propagation, where signals can travel this extended route under certain ionospheric conditions.

ROB: Good GPT...very good. You can have an extra helping of dessert tonight!

ChatGPT: Thank you, Rob! I’ll savor that virtual dessert—maybe a double slice of binary pie topped with whipped data. 😄

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So! This AI thing DOES have a sense of humour! It even put the emoji at the end of its reply! Cheeky!!

73 and good DX

Rob Wagner VK3BVW