I've just checked 4 phones. One only has what might possibly be such a port. The three different Nokias appear not to have. The Sony Eriksson Z750i has something that might be such a port but the the internal details do not look convincing.

I'd be more worried about the VSWR (variable Standing Wave Ratio) of this bodged up antenna in a can. Aerials come in different types but just supposing that we are talking about full wave antennas, the antenna needs to be the same length as the transmission wavelength (or an exact multiple) - ignoring for this purpose 1/4 wave, 5/8 wave and 3/4 wave antennas. If it isn't then a proportion of the broadcast power will be reflected back into the transmitter. Unless your VSWR is less than 1.5 to 1 you stand a real chance of destroying your transmitter. A book about CB or amateur radio aerials will tell you more.