vhf antenna install

[farmboy]

I have been cruising around in a 22' searay cutty since the 70s. I attempted a radio/antenna install 20 years back without good results as far as broadcast distance is concerned. This time, a new cobra vhf radio and shakespere mariner 8' antenna are going in with the hope of better results.

I have some confusion caused by the various antenna install instructions I have been reading. The coaxial cable is 20' and I need 3' to get from the mount to the radio. I am lucky to have the space to stow all 20' of cable if need be. The manufacturer's instructions say that I can cut the cable to the length I need. Other instructions say to leave it full length.

Back when I installed the first radio, a FCC license was required. That is no longer a requirement but they have specific rules for antenna installation. They say the antenna must be installed 10' from the passenger compartment and 3' up over the top of the passenger compartment. I hope I am mis-reading that as that would make the install difficult and ugly.

I would enjoy hearing the pros and cons of cutting the cable, leaving it at full length or any other tips anyone might share. TIA

 

[firehog6305]

Re: vhf antenna install

just leave the cable long, loop it like a rope and use zip ties, you never know when you might need to move the radio, just look at other boats and see where they have installed their antennas and then decide from there

 

[Gary H NC]

Re: vhf antenna install

I agree,cutting the cable length can actually hurt the performance of the antenna.Tie it with the zip ties but leave it in the largest loops possible.

 

[bruceb58]

Re: vhf antenna install

Cutting the cable will not hurt the performance of the antenna.

http://shakespeare-marine.com/faq2.asp?ReqNum=1

 

[QuadManiac]

Re: vhf antenna install

Cutting the cable will not hurt the performance of the antenna.

http://shakespeare-marine.com/faq2.asp?ReqNum=1

As long as a quality solder or crimp job is done on the new connector.

 

[freddyray21]

Re: vhf antenna install

I don't know about vhf antenna per se. On CB's the length of the cable can affect the swr ratio and that is why they said don't cut the cable. Properly installed the swr was adjusted for the length of the cable at installation. Shortening it or lengthing it would affect swr thus performance.

 

[QuadManiac]

Re: vhf antenna install

I don't know about vhf antenna per se. On CB's the length of the cable can affect the swr ratio and that is why they said don't cut the cable. Properly installed the swr was adjusted for the length of the cable at installation. Shortening it or lengthing it would affect swr thus performance.

That's because CB antennas were almost always a compromise between proper impedance and size. Most people didn't want a 11' whip on their VW bug, lol. Tuning the cable length helped match to a mis-matched antenna. Quite often, also, CB antennas were installed as 'arrays' with 2 or more in an installation. Cable length in this arrangement was critical (as was antenna spacing) to maintian the proper phasing of the antenna signals.

This should not be a problem with a quality VHF antenna.

 

[farmboy]

Re: vhf antenna install

i appreciate the advice and since I have the space for "rope coils", I will leave the 20'cable intact. The connection will be soldered not crimped. Does anyone have any thoughts on the "safety" considerations in regards to antenna mounting?

 

[Boatist]

Re: vhf antenna install

Mounting all depends on the type of boat. Most trailer boat you are going to want to mount the antenna on the front deck in a position where it can be laided down on the side of the boat when going down the HWY. For more height use a good antenna extension and a heavy duty mount. For long extensions you need a brace to the side of the cab but still needs to be able to lower to the side of the boat for trailering and bridges.

A normal 8 foot 6 DB gain antenna mounted 3 foot above the water will have a range of about 5 miles so talking to another boat with a like antenna your total range is about 10 miles over open water. Talking to Coast guard or marine operator can be 80 miles or more due to the height of Coast Guards antenna. On the other hand in a river channel with leves on both side and a tree lines bank range can be much less that 5 miles.

Get a good quality antenna like a Shakespear 5225 for a strong set up.