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Author Topic:   RG-58 Connectors and Splicing
DVollrath posted 05-03-2013 12:11 PM ET (US)   Profile for DVollrath   Send Email to DVollrath  
Hi. I am beginning to install the antenna for a VHF radio. The length of cable that came with the mount is not quite sufficient, and I'll need to extend it as well as attach a connector at the radio end of the transmissionline. I'm fairly handy with a soldering iron, but would like to get opinions about the best way to end up with a longer coax run with a connector on the end. The break in the cable should fall just inside of my console, so it will be somewhat protected.

Can splicing the cable be done by mortals without introducing too much of an impedance discontinuity?

If not, would folks recommend installing an additional pair of connectors for forming the splice?

What style of connector is recommended (soldered, crimped or other)?

Thanks for your help.


jimh posted 05-03-2013 12:51 PM ET (US)     Profile for jimh  Send Email to jimh     
For a small, flexible transmission line line RG-58/U, it is generally not practical to make a splice connection of two lengths of cable to each other without using some sort of connector(s).

If the transmission line must be extended, it would be prudent to use a low loss cable to make the extension, particularly if the length of the extension is going to be longer than a few feet.

I would approach this problem as follows:

Plan the installation so that the new extension cable is made from a low loss cable, such as LMR-400 coaxial cable. Plan to make the LMR-400 segment as long as possible, and reduce the RG-58/U segment as much as possible. The LMR-400 cable is not very flexible, so plan for its segment to be installed with limited bends and bends with a large radius. If this is not possible, use LMR-400-UltraFlex, another low-loss cable but with much better flexibility than LMR-400.

Purchase a pre-made cable made with connectors installed. There are many vendors offering this sort of on-demand custom cable fabrication at very attractive prices, usually no more and sometimes less than the cost of the cable and connectors when purchased individually in small quantities.

On the radio end of the cable specify the usual PL-259 connector. On the antenna end of the extension cable, specify a Female UHF-series cable connector. On the original RG-58/U from the antenna, install a standard PL-259. The original cable will connect to the extension cable directly, without any added adaptors because of the cable-end female-UHF fitting on the extension cable. If this arrangement cannot be obtained, then resort to getting a PL-259 on the extension cable and use a UHF Barrel adaptor (female-to-female) for the connection between the original cable and the extension cable.

Generally I avoid crimp connectors because the tooling needed is usually very expensive, typically more than the cost of ten connectors. Unless you plan to become a fabricator of cables, it will not be cost effective to use crimp connectors due to the high cost of the tools needed. Paradoxically, crimp connectors are often much less expensive than the traditional clamp or compression connectors they replace. For example, a traditional UG-88 connector is now about $15 while a crimp replacement might be $3 or less. However, if you only plan to install one, you don't need special tooling for the traditional connector, and you might need a $75 tool for the crimp connector.

There are some RG-58/U female cable-end UHF connectors, but they typically are crimp connectors. They are also hard to find and order. If only a short extension is needed, you could use one of these and make the extension from RG-58/U.

One problem in the modern day with coaxial cable connectors is the enormous variety of them. There are so many different connectors, even in one series of connectors like the UHF series, that finding the exactly right connector is often difficult. You must carefully read a lot of catalogues to get what you want.

DVollrath posted 05-03-2013 01:02 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
Thanks for the reply Jim.

Regarding the connectors, are there truly marine-specific varieties, or are all basically the same construction. I see that Ancor has a line.


jimh posted 05-03-2013 01:07 PM ET (US)     Profile for jimh  Send Email to jimh     
There are no "marine" connectors that I know of. There are generally two kinds of connectors: the standard commercial connectors, and the almost identical connector that is qualified to military standards and cost three or four times more. The military uses the military grade connectors for military electronics. You don't need to pay four times more for the military grade.
jimh posted 05-03-2013 01:05 PM ET (US)     Profile for jimh  Send Email to jimh     
If the extension is short, only 5-feet, make the extension from high-quality low-loss RG-58/U cable. Use cable-end BNC series connectors for the joint. Use a standard UG-88 connector on the original antenna transmission line. Use a UG-89 cable-end female BNC on the extension cable.

The Amphenol part number and prices are

UG-88 = 31-2 = $5.64
UG-89 = 31-5 = $6.34


This will make a neat connection between the two transmission lines without needing a female-to-female adaptor.

jimh posted 05-03-2013 01:19 PM ET (US)     Profile for jimh  Send Email to jimh     
ASIDE: The use of crimp connectors in place of solder and clamp connectors often reduces the skill needed for the assembler. Installation of solder-on connectors requires very high soldering skill for small connectors like the UG-88 or UG-89 series. In contrast, an assembler installing a crimp connector requires no solder skill at all, and a much lower skill level overall compared to the solder and clamp connectors. For this reason, use of crimp connectors has become common in high-volume fabrication of cables with connectors.

I have been practicing soldering of electronic components for over 50 years, so I am rather skilled in soldering techniques, and I have some excellent tools for soldering. For those reasons, I have no hesitation in using solder connectors, even ones like the UG-88 which require very careful soldering for the center conductor pins and sockets.

17 bodega posted 07-04-2013 04:21 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
I have the need to replace a PL-259 connector that went bad on a low to mid grade antenna for my marine VHF. A low hanging oak tree broke the fiberglass shell on the antenna, and then at the same time, the PL-259 failed on me. In my case the cable separated from the PL-259 without damaging the connector or the cable. I have "taped" and reinforced the antenna (while a good one is on order) and am going to attempt to re solder the original PL-259 back to the cable...

has anyone repaired an existing connector? Any wisdom out there? Chuck? Jimh? Calling all techie nerds!


DVollrath posted 07-04-2013 04:28 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
If the separation was clean, I assume that this was a solderless connector. Is this correct?

I only have used the solder type, and just for this one application. I did need to reverse and redo it, so the soldered type connectors can be used again. Not sure about the others.


L H G posted 07-04-2013 09:07 PM ET (US)     Profile for L H G    
For years I have been using the Shakespeare gold plated brass marine grade PL-259 connector. It is model "Centerpin PL-259-CP-G".

They advertize "No measuring, no soldering, no stripping Installs in seconds using only wire cutters and pliers"

They are correct. Mine have worked perfectly and still do.

I have forgotten what it cost, but it is a bargain for the ease of intallation you get. West Marine and other boat stores have them.

For a splice, I buy two and the standard female/female connector.

17 bodega posted 07-04-2013 09:17 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
Thanks gang... I did buy the exact part you are referring to Larry, but I'm going to try to solder the old one and keep the spare in the boat box.

I'll let you guys know how it goes.


jimh posted 07-06-2013 08:36 PM ET (US)     Profile for jimh  Send Email to jimh     
How about wire nuts?
Chuck Tribolet posted 07-06-2013 11:26 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
How long is the cable on the antenna?

The low-end Shake antennas have a 15' cable, the Shake Galaxy antennas
have a 20' cable. It may be easier to get a different antenna.


jimh posted 07-07-2013 07:32 AM ET (US)     Profile for jimh  Send Email to jimh     
If just replacing a PL-259 connector, you can often re-use the old one. Just unsolder it, and clean it up a bit. If you hold the connector with pliers, you can heat up the solder on the existing connector, adding some new solder to get it nicely flowing, and then swing the connector against a stop, letting the molten solder fly off. (You have to do that in an area where you can let the molten solder fly; not on carpet!) Real PL-259 connectors have insulating material that can withstand a lot of heat. Junk PL-259 connectors with thermoplastic insulation cannot tolerate this, but you should not be using junk connectors, anyways.

You do not need to use gold-plated "marine" connectors. NASA does not use them on the space shuttle, so why should you use them on a boat? If you want a new connector, a standard Amphenol 83-1SP connector is a very good choice, and its cost is only $4.50. See ?qs=qhgJLQbFbXlx2vb4pGU9mQ==

You will also need a reducer-adaptor, which costs a whopping $0.62:

You can also use the Amphenol FCP series. These are a modified crimp connector. You can crimp the center conductor with just pliers, or, if you wish, you can solder it. The outer conductor is retained with a squeeze fitting. See these assembly instructions for more details:

Here is the connector, a $5.30 item: ?qs=%2fha2pyFadugKfK3KDUsrk%252bkRC750C6KBbWPnrUQZO9tFlBUokBbggA%3d%3d

17 bodega posted 07-08-2013 11:10 AM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
The cable appears to be about 10 feet [outside the fiberglass tube] which could mean it has been spliced on previously. I think your conclusion is correct Chuck... sadly this antenna has lived out several of it's 9 lives. The Petaluma River Bridge shortened the tip on this antenna years ago as evidenced by some 5200 and a rubber cap at the tip... the most recent damage was a clean break in the fiberglass shell, which may have damaged the wire inside.

I will buy a few of the connectors from Mouser. I have bought discontinued parts for vintage microphones from them on occasion and their parts seem top quality. Thanks for the tips!

Tweaking around with the electronics on small boats is loads of fun!

DVollrath posted 07-08-2013 02:16 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
Mouser is great. We use them for my work.


jimh posted 07-08-2013 09:38 PM ET (US)     Profile for jimh  Send Email to jimh     
[Moved new topic to its own discussion--jimh]

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