VHF cable connection

[SailorKeddy]

So I think I have RG8 cable going from my VHF to antenna ( based on 0.4" OD) and I need to connect two ends together before it goes in mast. There is an old screw type connector on one side that I snipped off (see pic)...what type of connector is this? How else could I connect some RG8 coax cable??

Thanks!

[transmitterdan]

The connector is type PL-259. It is also known as a "UHF" connector. There are various types such as crimp or solder. Which type you need depends on the skill and tools available. Solder takes the most skill. Crimp requires the right tools and some training.

[skipmac]

Hi SK

Everything you need to know to do this job is at this link. Easy VHF Connections Photo Gallery by Compass Marine How To at pbase.com

Compass Marine is on this forum under username Maine Sail. Expert in things marine electrical and more.

[SailorKeddy]

So all I see are male connectors....are there female PL-259 connectors? Or do I need two make and a female-female??

[skipmac]

Originally Posted by SailorKeddy

So all I see are male connectors....are there female PL-259 connectors? Or do I need two make and a female-female??

Don't know about where you're located but in FL to get a "good" marine electrician to come to your boat and do a simple job would probably set you back $100 at least. I emphasize good as this isn't an area where you want to cut corners.

You can buy antenna cable with one end already attached. If you're reusing old cable it might be worth investing in new, low loss cable like RG-213.

[SailorKeddy]

I have rg-213 going from my VHF to the base of my mast, then more rg-213 going up the mast to the antenna. I need to connect the two bare ends at the base of the mast. I've seen male connectors I can splice/solder on but no female. Do I need two male ends and the a female-female in the middle?

[tkeithlu]

It's called a double female PL259. Here's a link, although Google will take you to many other sources, including Amazon.

PL-259 Connectors, Adapters & Reducers | Amateur Radio Supplies

[skipmac]

i believe the female version of the PL 259 is an SO 239 and yes they are available for the cable but I used used PL 259s on both ends of my cable with a double female SO 239 the middle. The signal loss is almost zero if you use good connectors. Spend the money for Amphenol

[transmitterdan]

Originally Posted by SailorKeddy

I have rg-213 going from my VHF to the base of my mast, then more rg-213 going up the mast to the antenna. I need to connect the two bare ends at the base of the mast. I've seen male connectors I can splice/solder on but no female. Do I need two male ends and the a female-female in the middle?

Any ham radio shop will have what you need. Generally you put male connectors on the cable. If you need to join 2 pieces of cable together use a so-called "barrel connector" which is 2 female connectors back to back.



You can get them here and many other places:

Female UHF barrel

[continuouswave]

Originally Posted by SailorKeddy

So I think I have RG8 cable going from my VHF to antenna ( based on 0.4" OD) and I need to connect two ends together before it goes in mast. There is an old screw type connector on one side that I snipped off (see pic)...what type of connector is this? How else could I connect some RG8 coax cable?...

The connector you show is some variant of the PL-259 connector, part of the UHF-Series. I believe the nomenclature PL-259 was the USA Army part number, probably a holdover from wartime production in the 1940's. The series designator UHF is a bit misleading, as today no one would use a PL-259 connector at UHF frequencies. The PL-259 is a PLug and it makes with the SO-239, a SOcket.

To connect a PL-259 to another PL-259 requires an ADAPTOR, not a connector. The nomenclature used is sometimes 83-1J, the part number of a major manufacturer (Amphenol) for an in-series plug-to-plug PL-259 adaptor. The Army part number is PL-258, but this is not in common use in my experience (which goes back to the 1950's).

You mention two generic types of coaxial transmission line, RG-8 and RG-8X. Both these designators are now generally meaningless as there are no military specifications for them. You can buy coaxial cable marked RG-8 or RG-8x and get a wide variety of products of various quality.

In general, the RG-8/U Mil-C-17 specified cable was a single-shielded 0.5-inch OD 50-Ohm impedance cable with a contaminating black vinyl outer jacket. This has now long been superseded by RG-213 cable, a similar cable except the outer jacket is a non-contaminating black vinyl, often called a Type-II. In coaxial cable to be used outdoors in weather and sunlight, it is much preferred to use cables with non-contaminating jackets. There are also many very similar cable to RG-213 made by many cable manufacturer with their own designations. Cables with contaminating outer jackets tend to see increases in loss as the outer jacket vinyl contaminates the copper shield conductor.

The RG-8x cable was something of a hybrid cable in which the general dimensions of RG-59/U, a 75-Ohm cable were used, but the dielectric was changed to a foam instead of polyethylene and the center conductor diameter increased to get the cable impedance back to 50-Ohms. There has never been, to my knowledge, any Military Specification for an RG-8x cable. This cable is often seen in marine applications and comes is a very wide variety of quality. In my experience RG-8x is not a good cable to use--unless you buy it from a major cable manufacturer--as it has a non-contaminating jacket and the foam dielectric must not be subjected to any sharp bends. Migration of the center conductor in the foam is a problem with this cable, and particularly in hot climates. No professional antenna installer would ever use this cable.

In general for installing a VHF Marine Band antenna atop a tall mast, the transmission line loss should be carefully considered. A typical goal in any transmitter installation is to limit transmission line loss to less than 1-deciBel.

Here are some typical characteristic transmission line losses at 150-MHz for 100-feet of line for several grades of cable:

RG-58/U = 6.2 dB
RG-8x = 4.7 dB
RG-213 = 2.8 dB
LMR400 = 1.5 dB

With this data we find the maximum length at 150-MHz for a loss of 1-dB to be:

RG-58/U = 16-feet
RG-8X = 21-feet
RG-213 = 35-feet
LMR400 = 67-feet

If you want an optimum installation, choose the transmission line accordingly.

For connectors, the transmission line at the antenna must be fitted with the appropriate mating connector for attaching to the antenna. It sounds like a PL-259-type connector must be used in the situation under discussion.

There are many choice for a PL-259-type connector, depending on what transmission line you choose. Get a quality connector that is specifically designed for the transmission line. I am old-school and prefer solder connectors for the center conductor. Center contacts should also be captivated so they do not retract in cold weather and break contact.

If you buy transmission line from a vendor who offers a service to install connectors, I recommend taking that option. Most boaters do not have specialized tooling for installing modern connectors using crimps, and solder connectors can also be a problem, as they require some skill and possession of proper soldering irons.

If there is any weak point in a boat radio system, it seems like the transmission line connector is the number one suspect. In the case of a connector installed at the top of a tall mast, make every effort to use a proper connector, to remove strain from it, and to protect it from ingress of water.

[continuouswave]

Oops--meant to say that many RG-8x cables have a contaminating jacket. This really varies with the brand of cable.