VHF co ax cable to FM receiver

[H4B]

Hi folks

Prompted by the previous poster but not wanting to Hi jack his thread - I have my own cabling problem.

I have an old Lokata SSB receiver . Which I use as an FM radio and may one day use as a SSB . I have been using an indoor FM aerial (two copper wires which attach to the unit by two screw clamps marked FM antenna . This is OK but a bit untidy and always require re-arranging for best reception. I have now purchased a splitter intending to use the mast head antenna for both VHF and FM reception BUT how do I connect the co-axial cable to the FM antenna clamps on the radio ? Obviously - There is no Co-ax socket on the radio.

Thanks.

 

[crunderhay]

I've got one of those, don't know if it's exactly the same model but I'm sure there is a coax (TV type) socket on the underside at the back.

I'll check mine at the weekend and let you know.

Cheers

Chas

 

[Evadne]

The easy answer is to strip back the coax and make two wires out of the centre and shield, and either twist them into wires so that the screw clamps will accept them, or crimp a couple of ring or spade terminals on.

The biggest snag I can imagine is that the co-ax may be 50 Ohm or 75 Ohm, and the cable clamps may be designed for 300-ohm. This will reduce the sensitivity of the receiver, but should not kill it completely.

 

[bedouin]

As mentioned above, if you have screw terminals then that is probably for a 300Ohm balanced, whereas what comes out of the splitter will be a 75 Ohm unbalanced feed.

I would be a little concerned that that could impact the perfomance of the other side of the splitter. The correct solution is to use something called a "Balun" , Maplin sell one for about £1.50

 

[H4B]

Brilliant ! Thanks very much.

 

[William_H]

Yes I would discourage the use of the "splitter" . It is simply not necessary to risk interfering with your VHF Com radio operation.
A low level antenna will work quite well made of plain wire. (stuck to the inside of the roof of the cabin) (mine just runs about 1 metre along a shelf) For your radio 1 metre in each direction from each screw.

The radio is made to use a 300 ohm ribbon type balanced cable. You can as suggested use a balun as made for TV antenna with a pair of screws one end and a coax socket on the other end. The ribbon cable was common many years ago but has largely been superceded around here by coax. If the run is short (1ft) just use 2 pieces of light plastic covered wire.

Incidentally it is most likely there is a seperate antenna connection for a HF antenna for SSB reception. good luck olewill