Notes From Installation of an FME Connector

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
jimh
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Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
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Notes From Installation of an FME Connector

Postby jimh » Wed Aug 14, 2019 4:45 pm

NOTES FROM INSTALLATION OF AN FME CONNECTOR

In an earlier article (now appearing in the announcements at the top of this forum) I discussed use of a somewhat uncommon coaxial cable connector, the FME or For Mobile Equipment connector.

I finally got around to installing an FME connector on one of my coaxial transmission lines. The antenna on this transmission line is on my boat, and accordingly I had to work on the boat to install the FME connector. The transmission line is RG-58C/U coaxial cable.

I ordered the connector, the adaptor, and the crimp tool from SHOWMECABLES.COM. If interested, here is the order list with part numbers and prices:

--FME Female Crimp ConnectionRG58    SKU: 223 $2.44	

--FME Male to UHF Male Adapter SKU: 238 $4.76

--Ratchet Crimper Tool for RG58,
RG59, RG62, RG6, RG141, RG142,
LMR-195, LMR-200, LMR-240,
and LMR-300 SKU: 93-100-002 $32.93


I had the parts shipped by USPS Small Package for about $8. The order arrived in about two business days. This means the first connector installed has cost me about $48. Most of the cost was in shipping and the crimp tool. The next connector installation will cost $2.44.

The center conductor contact for the FME connector is a solder-on contact. Soldering this contact will require good soldering experience, use of a very small solder tip, extremely clean conditions, and careful work. If too much heat is used the center insulation of the RG-58C/U cable tends to swell and increase in diameter. The fit of the center conductor insulation into the connector body is VERY tight, and no swelling can be tolerated. I found I had to carefully trim away some of the center insulation on the cable to obtain a fit of the cable into the FME connector body. This is a delicate soldering job, and even with about 60 years of soldering experience, I found it a challenge, particularly because I was working on the boat without the benefit off all my small-electronic tools, a portable vise, and a magnifier.

Also, I was soldering to the center conductor of a cable that had been in service for about 11-years. There is a tendency for the copper wire in older cables, even when tinned, to become a bit reluctant to take on more solder, probably due to some contamination of the surface from being in contact with the polyester insulating material for many years. A coaxial cable made just a short time before you try to solder to it will likely accept solder more easily.

When installing any crimp connector, be certain to pre-assemble all the parts of the connector that must be in place BEFORE you crimp the main ferrule of the connector onto the cable. When planning on using crimp connectors, I always order one or two extra connectors to permit re-doing a cable if a mistake is made. Once the ferrule is crimped, there is no going back to fix something.

The FME female cable-end connector for RG-58C/U cable has a very small diameter. It will pass through a 3/8-inch-diameter hole. The finished cable assembly with pre-installed FME should be easy to route through rigging tunnels, conduits, and tight passages.

The impetus for ordering and installing the FME connector was an intermittent problem with the boat radio. The radio seemed to be losing connection to the antenna. The existing PL-259 connector on the end of the antenna's transmission line at the radio was suspected to be the problem. I decided I would replace the connector. Rather than use another PL-259 and reducer, I opted to install an FME connector on the transmission line and use an adaptor to mate to the radio's SO-239 receptacle. Ironically, the connector was not the problem. Shortly after finishing the connector installation and trying out the radio, I discovered the actual problem. (I will mention the actual problem in another article.)

jimh
Posts: 6905
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Notes From Installation of an FME Connector

Postby jimh » Sat Aug 17, 2019 7:57 am

The very popular marine antenna manufacturer SHAKESPEARE is now proving some of their antennas with a pre-installed FME connector on the transmitter end of the antenna coaxial cable feedline. They seem to have adopted their own brand name for the FME connector, and they refer to it as “EASY ROUTE FME Mini” instead of the generic FME designation.