Different Versions of SO 239 Connectors!

In my recent post on Factors Affecting SWR, I had mentioned about splayed out inner connector of SO 239 on the SWR meter, as a reason for open circuit while connecting a PL 259 plug. I had a closer look at the SO 239 connectors on TM 261, IC 2730 and FT-710. I was quite surprised to find that they are obviously different from the SO 239 connector on the SWR meter! I could compare only the construction on external appearance and not the quality of material and method of construction of the connectors. I presume that it will be better for the more expensive radios than the much cheaper SWR meter.

There are a couple of spikes on the PL 259 to fit in to the notches on SO 239 connectors. While the SO 239 connectors on the SWR meter had only four notches, those on the radios had multiple such notches. I presume that it is easier for the PL 259 to fit in to one set of multiple notches in the SO 239 connector on the radios easily than in the limited number of notches on the SO 239 connector of the SWR meter. When we try to tighten the screw, if the notches are not properly alligned, there is every chance of damage to the inner connector of SO 239 and an open circuit in the long run. Once I shaped the splayed inner connector using a nose plier after seeing the HIGH SWR indication.

I presume that multiple such attempts while changing antennas are the reason for the splayed inner conductor of SO 239 which I noted on the SWR meter. Improper connection with open circuit immediately triggers HIGH SWR alarm indicator in the radio and shuts down output to protect the RF final amplifier from damage due to mismatch. Adding antenna switches to the circuit will probably prevent such damages as we do not have to change antennas frequently. Another option is to use a multi-band EFHW antenna. Even then antenna will have to be disconnected during thunder storms, which are not uncommon in this region. Antenna switches will not prevent lightning from entering the radio as the extra high voltage will jump across the open switch contacts.