VHF Antenna Cable Extension

Hello from England, A friend has given me a second hand fibre glass vhf antenna to be used as a spare for my fixed dsc/vhf radio. Unfortunately the antenna cable is only 2 feet long. Obviously the cable is too short.The cable is a standard marine type RG-58 with a PL259 connector. Is it possible to join it to a three length of RG-58 marine cable without effecting the radio performance too much? Thank You. David

Re: VHF Antenna Cable Extension

The coaxial transmission line between a transmitter and an antenna can be extended. Use transmission line of the same characteristic impedance as the original.

Adding transmission line between a transmitter and an antenna increases the loss in the transmission line. As long as the overall loss in the transmission line is held to a reasonable amount, there is not a great concern for transmission line loss.

Typically in Marine Band VHF radio installations the radio and the antenna are connected by about 20-feet of transmission line. This gives a transmission line loss of about 1-dB. If the length of the transmission line is to be greater than 20-feet, you should give some consideration to changing the transmission line to a lower-loss coaxial cable.

Re: VHF Antenna Cable Extension

Many thanks jherbert for your help. I only intended to add five feet or so to the original cabe so hopefully there would be only a little signal loss. Could any one tell me the best connector to use? Thank you, David

Re: VHF Antenna Cable Extension

joyceboat said:

Many thanks jherbert for your help. I only intended to add five feet or so to the original cabe so hopefully there would be only a little signal loss. Could any one tell me the best connector to use? Thank you, David

Click to expand...

PL259 connectors. The same as the one on your existing antenna/radio connection.

Re: VHF Antenna Cable Extension

I like brass..

Re: VHF Antenna Cable Extension

I'm reading that you want to add an additional length of co-ax to the existing 2' on the radio? You'll need a PL259 female-female coupler like this;
http://www.google.com/products/cata...TJqHEpHIM9iyga4H&sa=title&ved=0CAcQ8wIwADgA#p

Then you'll need to buy or make a "patch cord" consisting of a length of RG58 co-ax and 2- PL59's;

http://www.radioshack.com/product/index.jsp?productId=2062628
PL259's are made for RG6 (much bigger) so you'll also need 2 reducer adapters for RG58 co-ax.

3-5 ft cords are readily available already made up.

BTW, your radio, antenna, and co-ax are 50Ω impedance. Do NOT use RG59 co-ax, that's 75Ω, it's for TV/cable/video applications.

Re: VHF Antenna Cable Extension

Just a quick up date. I have used the advice given and the radio is now up and running. I have not noticed any reduction in the radio performance so I can safely say job well done. Many Thanks to every one for their help and advice. Regards.David (joyceboat) England