RG 58 A/JJ - Something making a hole in my boat

Hello all. I was hoping someone could help me identify whatever these are that appear to be making holes in the bottom of my boat. I have two of them just off the centerline and just behind my engines. They each have a cable coming from them labeled RG 58 A/JJ, which makes me think they used to be for some type of electronics that are no longer on the boat. Does anyone happen to know what they are or what they were for?

jsplichal2 said:

Hello all. I was hoping someone could help me identify whatever these are that appear to be making holes in the bottom of my boat. I have two of them just off the centerline and just behind my engines. They each have a cable coming from them labeled RG 58 A/JJ, which makes me think they used to be for some type of electronics that are no longer on the boat. Does anyone happen to know what they are or what they were for?

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My guess is that they are transducers of some sort.

Where does the cable trace to?

Transducers for sure.

Looks like depth finder transducers. How is your President 41? We have one also.

Well now I feel like an idiot. I just assumed the depth sounder was on the transom - for no particular reason. Once the cable reached the large bundle leaving the engine room I stopped looking since I assumed it was for something already removed. Love the President. And it is good for a laugh everytime someone thinks I have this huge love affair with Bush #1.
Thanks guys.

RG-58 is Coaxial cable. RG = Radio Guide. It is used for low-power signals and RF connections.

The 58 class has an outer diameter of 0.195 inches, 50 to 53.5 ohms impedance, and can handle up to 500 watts of HF (High Frequency) power.

RG58/U has a solid center conductor of 20 AWG bare copper. Its capacitance is 28.5 pF per foot.

RG58A/U has a center conductor of 20 AWG stranded tinned copper. Its capacitance is 30.8 pF per foot.

RG58C/U has a center conductor of 20 AWG stranded tinned copper. Its capacitance is 30.8 pF per foot. It's outer jacket is a different material than RG58A/U.

RG-58A/U or RG-58C/U was once widely used in "thin" Ethernet (10BASE2), for which it provides a maximum segment length of 185 meters. However, it has been almost completely replaced by twisted-pair cabling such as Cat 5, Cat 6, and similar cables in data networking applications.

RG-58 cable can be used for moderately high frequencies. Its signal attenuation depends on the frequency, e.g. from 10.8 dB per 100 m (3.3 dB per 100 feet) at 50 MHz to 70.5 dB per 100 m (21.5 dB per 100 feet) at 1 GHz.

I have no idea what R-58 A/JJ is. I'm only familiar with JJ as a designation for the BNC connectors on r58m like BNC-A-JJ (A JJ adapter).

Probably something old that they don’t make anymore. Thanks.