VHF Antenna and Wiring

[transmitterdan]

Additional reasons for having a coax joint (female barrel connector) besides ease of mast un-stepping:

1) With a simple pigtail made up and ready a handheld can use the masthead antenna in an emergency if ships batteries fail.

2) When leaving the boat for a long time disconnecting the joint can help prevent lightning damage to the VHF radio. Helpful if back of radio is hard to access. Remember to reconnect and seal if outside before going out again.

3) Makes a convenient place to install a VSWR/power meter to troubleshoot antenna and radio problems.

Also, the joint does not have to be outside for keel stepped masts. Even deck stepped masts with the right thru deck fitting (inverted J pipe) can keep the joint below deck.

[continuouswave]

Originally Posted by S/V Illusion

Properly installed connectors create no loss.

The key word there is "properly."

[ka4wja]

elittke,
Well, you got some good answers and advice here, and I'm sorry I'm coming in late as I hope to get you some definitive answers!!

BTW, this subject comes up here every few months, and I will post links to recent discussions, where you will find ALL the details (and minutia) that you could ever want (or need) about this...
But, first some direct answers...


1) First off, if it's original cable...replace it, along with the antenna!!
And, even if it isn't original....unless it's really good quality stuff, with connectors properly installed and waterproofed, if it's more than 5 years old...replace it!!!


2) Secondly, with the C38, you've got about a 75' run of coax...so, I would never recommend RG-58!!
And, only recommend RG-8x if that was all you could find...and/or that's all that will fit in the mast...

RG-213 (a good quality, name-brand RG-213), with connectors properly installed and waterproofed, will last you a couple decades without issue!!
This is thick cable (0.405" in dia)....so if you cannot fit this thru your mast conduit, then a thinner cable might be called for...

If you require a thinner cable, a good-quality RG-8x (such as Belden, Commscope, Times, Davis) will also work well for you...
Or, if low-loss is a concern of yours, you can use LMR-240UF....(note the "UF")....this has about the same loss of the larger RG-213, but is not as robust and more attention to detail (such as waterproofing) is recommended...

Please take note here (and in the below referenced posts), that using LMR-400-type (or "9913-type") cabling is completely unnecessary in our applications!!
The slight reduction in cable loss versus RG-213 is virtually unnoticeable....and with the extreme margins built-into the Maritime VHF communications system, the 1/2db differences are moot!
Also, please do NOT even attempt to use any "solid-center-conductor" coax!! (like LMR-240, LMR-400, etc.)...especially as these cables use a copper-clad, solid aluminum center-conductor, which canot be kinked, etc., and is a real pain to work with...(and, anyone want to guess what happens when you get salt water into a copper/aluminum connection!!)
If you find it necessary to use a lower-loss cable than RG-8x, then using RG-213 is best...or if that will not fit, then use LMR-240UF (note: the "UF", as this denotes a stranded copper center conductor)


3) Understand that no matter what cable you select, as long as the connectors are properly installed, you should notice an improvement versus your old (original??) cable....
But, remember that caveat...."connectors properly installed"!!!



4) Also, please take note that the myth of "connectors create loss" is just that: A Myth!!!
Please see photo....

23 different connectors and adapters (and a short piece of RG-58), in series....with 100 watts of RF at 28.5mhz....losing 5 watts (or 5%), which is a power loss of 0.44dB....
And, some of these connectors are not even RF connectors (F, RCA/phono, etc.)!!
So, as you can easily see....worrying about a possible 0.02dB loss is ridiculous!!

Now, corroded connectors creating loss, intermittent connections, poor performance, etc....yes, all of those are true....but that's not the fault of the connector, but of the installer!!
So, make sure you weather-proof all external connections!!! (I prefer heatshink around the cable/connector, and 3M 66 tape as well....and 3M 66 tape around the male-to-female connector attachment / junction)

So, as long as the "splice" you refer to is a PL-258 "double-female" (aka "barrel"), preferably an Amphenol PL-258....and two properly installed PL-259's on the cable ends...this is not only perfectly fine but also a very common practice (both on boats and on-shore!)....
Again, just make sure it is weatherproofed!!


5) As for "the antenna":
The Shakespeare 5215 series antennas are the defacto standard....(these replaced the older Shakespeare 4200 Mariner a few years ago, but you can still find the 4200 on-the-shelf in some stores...either one will be fine...)

They are a full-size, half-wave, end-end, SS whip, VHF Marine antennas, with a SO-239 female connector on the bottom (allowing you to connect your own coax, test the antenna/coax, etc...)

The current models are the 5125 Classic and the 5215 Classic AIS (the same antenna, with the whip cut about 1/2" to 3/4" shorter)

5215 Classic AIS Squatty Body® Antenna | Shakespeare Marine Antennas

5215 Classic VHF Squatty Body® Antenna | Shakespeare Marine Antennas

I highly recommend these antennas....and recommend against antennas with the coax already attached (especially those with RG-58 attached!)



6) As for the exact procedure....
It is always preferable to put all wires thru the mast conduit together / all at the same time....(you can do it piece-meal, but it is a real pain!!!)
So, if you're going to replace the VHF coax, you should pull out ALL the old wiring in the mast conduit, and either replace it all, or at least separate the VHF coax, replace it with new coax, and then pull all the wiring in/thru at once...
Usually stagger the ends by a few inches, so that you don't have one big "bump" to pull thru...
Depending on your connectors, and mast conduit size, you may be able to pull 'em thru with connectors attached (but usually this is a pain)...
Best to feed the fresh cabling IN from the top, pull from the bottom....especially if you cannot fit the connectors thru the mast conduit, as this allows you to have a fresh/clean (professionally assembled/installed) connector at the masthead....and you can either install the bottom connector at the mastbase or nav station, as needed...

Pulling wire thru the conduit is an easy-peasy two-man-job...but a pain to do alone....
But, spend $10 on some "wire-lube" (available in all electrical supply houses, home depot, lowes, hardware stores, etc.), it will make ur wiring slide thru with ease!


If you've never assembled coax connectors before, best advice is to buy professionally assembled cable assemblies....
I recommend Texas Towers, DX Engineering, or Davis RF....
Texas Towers, Coaxial Cable Page
Texas Towers, Coax Jumpers Page

https://www.dxengineering.com/search...ble-assemblies
https://www.dxengineering.com/search...and-connectors

Davis RF Co. - Amateur Products
Davis RF Co. - Coax Cables


FYI, I've done business with all of these guys for years...all great companies to do business with....(although Davis is my fav, they don't have pre-made assemblies on the shelf, they're made-to-order, so they can take a while)

OR...

Or, you can buy the PROPER crimp-type connectors from these above sources (and the proper crimping tools), and follow the procedures/instructions with the crimping tools, and make up your own cable connections....
[Note: these are NOT the DIY-type connectors sold in marine stores! Do NOT attempt to use them!!! No matter how good "some guy" says they work!!]

But, I recommend against any layperson sailors attempting to use "solder-type" connectors!!!
This usually results in shorted connections and/or very poor connections....and at best, short-life-span / unreliable connections!!
(if you know what you are doing, there is nothing wrong with a Belden RG-213 to Amphenol PL-259 soldered connection....I've got dozens of them that work perfectly 30 years on!!! But, if you don't know how to do it, or even worse are using a "low-loss"/"foam-dielectric" cable, then it is a disaster waiting to happen!!

Maine Sail's / Compass Marine's excellent pages explaining "how-to" solder-type connectors is good...and, if you decide pre-made assemblies are too expensive (??) as are the expensive crimping tools, and decide on solder-type connectors, their page is a good how-to reference..
Easy VHF Connections Photo Gallery by Compass Marine How To at pbase.com

Originally Posted by elittke

On my 1983 Catalina 38, I would like to replace the VHF antenna and all the wiring for the antenna that goes from the unit to the masthead. With the mast in my backyard I looked at the wire as it enters the base of the mast and noticed a loop and splice of some sort? All in the same single wire? What would be a reason for boatyard to place a loop and splice? And when I get new wire and antenna, any recommendations on the best ones to use? And will I need to attach the ends after running the wire up thru the conduit? Any special tools required for that? Any advice on this project is appreciated!

Please have a look at these postings, where you will find all you will ever need to know about this!!

http://www.cruisersforum.com/forums/...ml#post1934240

http://www.cruisersforum.com/forums/...ml#post2079533

http://www.cruisersforum.com/forums/...ml#post1887668

http://www.cruisersforum.com/forums/...ml#post1802846

http://www.cruisersforum.com/forums/...ml#post1882988

http://www.cruisersforum.com/forums/...ml#post1682529

http://www.cruisersforum.com/forums/...ml#post1876295


http://www.cruisersforum.com/forums/...ge-149499.html

http://www.cruisersforum.com/forums/...ld-130803.html




I do hope this helps...


Fair winds..

John

[mdbrown]

I don't think you want to use the AIS antennas for your voice transceiver do you? The AIS frequencies are 6MHZ higher...do the AIS antennas have that wide of bandwidth?