Coax Connectors and cables

Jim Nolan (
Fri, 10 Dec 1999 08:49:43 MST

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West Wight Potter Website at URL
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>From: Rye Gewalt <>
>To:, Potter List <>
>Subject: Re: Coax Connectors
>Date: Fri, 10 Dec 1999 05:33:57 -0500
>Charles Falk wrote:
> > Would a couple of BNC or TNC connectors on RG58 pigtails be better than
> > a PL259 on the cable from the mast connecting to an SO239 bulkhead
> > connector on the cabin roof?

The UHF connectors can handle alot more power than either BNC or TNC.
UHF~2kW, BNC~10W TNC~25W. Also the UHF is less bothered by corrosion because
of its large area. A UHF connector that can feed through the cabin roof is
available from Pasternack Enterprises 949-261-1920, Irvine, CA. It is part
#PE9114 UHF female to UHF female bulkhead mount. It costs $8.95 in single
piece quantities. I would cover the outer portion with a rubber cap when it
is not in use.

Do not splice coax cable. You can get away with splices in short runs (less
than 12" at 150 MHz) but on the boat the cable is 20-50 ft long. Any splice
or impedance bump will seriously limit the match between the antenna and
radio and could in some cases burn out the radios final amplifier. Use
connectors to join cables.

Also a better cable than RG58 and still the same size is RG142. It has half
the loss but costs about 4 times as much. RG58 will have about 3 db loss per
100' at 150 MHz and RG142 will have about 1 dB. In a typical boat
installation you will get about 60% more power to the antenna using RG142
over RG58. RG58 is .40/ft in 100' qty, RG142 is $1.63/ft in 100' qty.

Over and out,

Jim Nolan P-19 #426 Panache

>I dunno.... Upon further reflection, I think that the SO239 connectors are
>probably best because they are big and tough. BNCs are small, but one kick
>would probably break them. The difference in loss is minimal when compared
>to coax losses and probably needn't be a major consideration.
>There should certainly be only one set of connectors in the cabin top
>assembly -- partly because of loss, but also because electrical connectors
>are a major point of failure -- particularly in external marine
>installations. Pigtail connection are always a problem with coax as they
>provide a major impedance "lump" with the resultant losses and should be
>Where are you putting the connector? I have been thinking about putting
>mine under the mast near the front so that when the mast is raised the
>connector is hidden in the center core of the mast -- which would provide
>both a degree of environmental and physical protection. That would put the
>connector close to the post in the cabin, but I think that's where it
>be located.
>About the only drawback to such a location would be that the coax connector
>would be in the way of the mast when it is down and bolted into the
>"transport" condition.
>From a reliability standpoint, it might be best to eliminate the connector
>at the mast all together and run the cable thru the cabin roof using some
>sort of clever feedthru -- but that has all kinds of limitations for
>sailors. Probably not an idea worth pursuing.
>It's a nice winter problem to reflect upon as I am planning to install VHF
>over the winter also.
> >
> >

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