Englishman,
The string you are using is too small gauge that is why can do only 6ft.
I have done not 6 but 60ft, that was when i was a kid.
Also dont use beer cans, they don't have good acoustic (sp?)
How do you ring the other party? I have a patented ringing design for a 'can' phone kit, distributors wanted.
Ah, if you are interested in a trasatlantic (sp?) 'can' phone kit just let me know.
As usual on a tangent, but can we see an analogy (hint WT) in the word of the scottish inventor:
"Leave the beaten track occasionally and dive into the woods. Every time you do so you will be certain to find something that you have never seen before. Follow it up, explore all around it, and before you know it, you will have something worth thinking about to occupy your mind. All really big discoveries are the results of thought." ? Alexander Graham Bell
PD
More on wi-fi canntenas later.