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Old 11-23-2011, 05:58 PM
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Default Splicing VHF Antenna Cable

How do I do it?

Not half ass, but top notch.

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Old 11-23-2011, 09:45 PM
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The coaxial cable between a VHF Marine Band radio and its antenna is a transmission line conductor, and the characteristic impedance of the cable is an important consideration in the overall radio system. Small, flexible coaxial cables like RG-58C/U are seldom, if ever, spliced when used as transmission lines at VHF frequencies because the splice will typically introduce an impedance discontinuity that will affect the radio system. Since these transmission lines are usually quite short, typically 20-feet or less in length, the whole line is replaced in preference to making a splice.

If you must use the existing cable, the best method will use two connectors. Install a connector on each side of the cable break, and then mate the connectors. For a small cable like RG-58C/U I recommend using BNC-series connectors. The advantage of the BNC-series is that you can easily obtain both a male and female connector for cable ends.

The least attractive method, although perhaps the one most used by boaters, is to install two PL-259 connectors and mate them with a UHF-Barrel or dual female connector. This is actually quite an ugly solution, and I don't recommend it.

The Mini-UHF connector is another connector available in both male and female gender for cable end use, but they are difficult to acquire in small quantities.
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Old 11-24-2011, 06:44 AM
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If you've never installed coax cable connectors before, I strongly suggest you find a pro to do it for you. I agree that you should avoid doing these types of connections but it is done almost universally on sailboats that have their VHF antenna on top of the mast. The connection is done near the mast step so the mast can easily be disconnected for removal. Any impedance "bump" caused by properly installed connectors is of absolutely no consequence. PL259 connectors are readily available in male and female variety as are mini-uhf types, even in small quantities. The problem with many types of connectors that may be an option is that they require special tools for installation that the DIY won't have, don't have experience with or want to pay for. Someone here will probably suggest using the Shakespeare Center-Pin connectors. They are very simple to install but I strongly advise against them. I'm a professional in this business and the number one problem I find in DIY communications equipment installations is faultily installed coax connectors. And don't let anyone here mislead you about crimp type connectors being inferior. They aren't. Here are some that I have installed. They are, solder type PL259 on RG8, crimp/solder PL259 on RG58, female mini-uhf on RG8x and crimp/solder PL259 on RG8. The male/female mini-uhf or male/female bnc are the best for RG58 or 8x as they are low profile and easier to weatherproof as opposed to the bulky PL259's.



Eric

Last edited by fairbank56; 11-24-2011 at 06:56 AM.
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Old 11-24-2011, 06:20 PM
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Thanks for the advice.

I am not splicing a section of cable together, but rather putting a male end that plugs into a VHF on a cable end..... It's been cut off.

Can I find the parts at a West Marine or similar?
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Old 11-24-2011, 08:00 PM
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Sure. There will be many here who would not use these but... if... properly crimped down a little bit at a time all around and around after applying a little diielectric grease to the cable end and insulation that will be crimped into and covered, the Shakespeare gold-plated Centerpin Solderless PL-259-CP-G connectors are IMO far and away the easiest to install right the 1st time and according to Shakespeare are just as relaible as the difficult-to-solder-correctly for non-pros old-style PL259's. . For: RG-8X or RG-58/AU coax cable


http://www.shakespeare-marine.com/co...ck=PL-259-CP-G

Last edited by TTaxi; 11-24-2011 at 08:12 PM.
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Old 11-24-2011, 08:52 PM
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Originally Posted by TTaxi View Post
and according to Shakespeare are just as relaible as the difficult-to-solder-correctly for non-pros old-style PL259's. .
Well of course they are going to say that. I will tell you that they are not very reliable at all. Iv'e replaced a lot of these connectors. Yes, they are readily available from West Marine and are very easy to install. The main problem is with the shield connection. There are six "fingers" that must be crimped so that they each penetrate the cable jacket and come into contact with the cable shield. There is no way to tell how many or how well the fingers are making contact. A continuity check will only tell you that maybe one small portion of one of the fingers is making contact, and just because there is continuity right after you install it, doesn't mean it's going to maintain that contact. There is nothing maintaining pressure on the fingers to hold them in place. The cover that goes screws over the fingers is just a cover, it does not contact and/or put pressure on them. In a true crimp connector, the cable shield gets sandwiched between two pieces of metal with one of them getting permanently crimped with a specially sized die in a crimp tool. There are also issues with the centerpin connection to the center conductor of the coax cable. Installing this type of connector will be the easiest solution for you but it will most likely cause problems in the future. You said you wanted a top notch job, not half ass. Using this connector is the half ass way to do it. Here is an example, one of many that I have, of what happens. In the first picture, none of the shield fingers had made contact with the coax shield. The second shows the center pin not going into the center of the coax center conductor, but going off to the side distorting the cable. Iv'e got a box full of used centerpin connectors along with one inch pieces of coax showing why these connections fail.

Eric




Last edited by fairbank56; 11-24-2011 at 09:14 PM.
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Old 11-24-2011, 09:22 PM
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Fairbank, good job, pictures dont lie!
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Old 11-25-2011, 03:19 PM
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I just went through this and used the Shakespeare gold-plated Centerpin Solderless PL-259-CP-G, against the advice of those on this forum. I was wrong in taking this shortcut. My VHF range is minimal now so I am going have to do it all over again, this time I will do it the right way. Listen to Fairbank56, it may be easier to hire a electronic person as he suggested because this job is a pain in the ----.
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Old 11-27-2011, 06:31 AM
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I ended up using the PL259 and soldered them. I think they turned out pretty good, hopefully they work like they should.



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Old 11-27-2011, 07:29 AM
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Not to pick a nit but the last photo is NOT considered a good solder job on the PL-259....not enough heat. A well executed solder will be bright and shiny as this example is, but will be concave as opposed to convex.
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Old 11-27-2011, 07:57 AM
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Not to pick a nit but the last photo is NOT considered a good solder job on the PL-259....not enough heat. A well executed solder will be bright and shiny as this example is, but will be concave as opposed to convex.
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I agree. It looks like a cold solder joint. The idea with soldering is to get the joint hot so the solder flows in to the joint easily. It looks like the solder is on the wire and the plug itself did not get hot. Not picking but better safe than sorry.
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Old 11-27-2011, 08:18 AM
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Thanks to all for the great pics and discussion. Historically, my connections have been successful, but I am wondering if I am at a disadvantage because of the soldering tool I use, which is the Portasol pictured here. I have never been able to duplicate the beautiful job shown in Eric's picture. Is it me or the tool?
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Old 11-27-2011, 09:50 AM
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Quote:
Originally Posted by Pez Vela View Post
Thanks to all for the great pics and discussion. Historically, my connections have been successful, but I am wondering if I am at a disadvantage because of the soldering tool I use, which is the Portasol pictured here. I have never been able to duplicate the beautiful job shown in Eric's picture. Is it me or the tool?
Both. You because you don't know to use a soldering iron with a lot more power, and the tool because it doesn't create enough heat to solder something as large and heavy as a PL 259 connector.

There is a lot of information on proper soldering on the Internet. Do a search and study it.
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Old 11-27-2011, 09:52 AM
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I agree. It looks like a cold solder joint. The idea with soldering is to get the joint hot so the solder flows in to the joint easily. It looks like the solder is on the wire and the plug itself did not get hot. Not picking but better safe than sorry.
That's exactly the problem.
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Old 11-27-2011, 10:41 AM
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Balls of solder sitting on top of the holes is typical and is a clear indication of an improper solder job. The braided shield of the coax should wick the solder down into the hole creating a concave appearance (same goes for the center conductor) like the one in the first photo below. Excess solder outside of the hole serves no purpose. You need to use an iron that has lots of mass so that the heat of the iron is not instantly and significantly reduced when you apply it to the connector. This is why small irons and even soldering guns should not be used. The tip of a gun gets very hot very fast but has no mass to prevent heat drawdown. I use a weller SP120 that I have filed the tip for the best contact area with the PL259. It should only take 3-4 seconds to solder the shield. It's an art that takes practice and the proper iron to achieve good results without damaging the cable.

Eric





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Old 11-27-2011, 10:57 AM
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Thanks Eric.
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Old 11-27-2011, 05:25 PM
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Here is a link that I thought was very good on PL259 soldering. Certainly concur with Fairbank56 comments!
http://www.thehulltruth.com/marine-e...pic-heavy.html
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Old 11-28-2011, 11:39 AM
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Iv'e actually been doing it that way for solder type pl259's on RG8x and RG58 for a number of years now and did a web page a while back showing the technique. I didn't mention it here cause I didn't want to add to the confusion. It is not "standard" practice to do it this way but it actually makes for a much more solid connection.

Eric
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Old 11-28-2011, 11:51 AM
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fwiw, the iron that fairbanks mentioned is 120 watts. A typical radio shack iron will be 20 or 25 watts.

They aren't typically interchangeable.
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Old 11-28-2011, 01:02 PM
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I just ordered a 120W iron off the net. That was my cyber monday purchase! Thanks Fiarbank56 and Thataway.
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