Feedline aboard ships

[Radio KH6O]

My 3 year career as a CW operator was at a shore station (NMO). 

The shipboard radioroom photographs I see posted appear to show parallel conductors routed to throughwall insulators.

Are parallel feedlines typical aboard ships?

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73,

Jeff KH6O

[D.J.J. Ring, Jr.]

What you are seeing is two separate feeders made of copper pipe.

Ships were required to have a minimum of two antennas: a Main antenna and a Reserve antenna.

Ships were also required to have a complete batter powered radio station, we usually called it our "Reserve Station". 

We had to test the reserve station daily and log the test results in our radio telegraph logbook. 

2024 February 4

0000 New Radio Day begins, continuing on watch. 

0015-18 500 kHz Silent Period Observed No Signals Heard Since January 1999.

0019 500 kHz Reserve Transmitter on battery, 1.2A/Reserve, 3.3A/Main, Reserve Receiver OK on mains and batter. Reserve emergency battery lighting OK. Battery on charge, measures 1255 Specific Gravity. Station clock wound, checked against WWVH, 2 seconds slow, reset to correct time. 

One copper pipe was for reserve antenna, one for the main antenna. These two feeders passes through standoff insulators to the outside deck where using a combination of copper pipes and heavy copper wires were routed to the approximately ten foot high antenna trunk which is the proximate terminus of the main and reserve antenna systems. 

HF transmitters generally used either one of the two antennas with the copper pipe feeders or a coaxial cable system with remote antenna tuner on the Bridge deck. These usually had vacuum variable capacitor and tunable coil with a standing wave detector and null seeking logic motor control and reversable motors for both the capacitor and the inductor. 

See attached photo of an antenna trunk. 

73

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[Radio KH6O]

So is each copper pipe acting as part of the wire antenna, or is there an inner conductor within that pipe so that the inner conductor and pipe together are working as a coaxial feed?

[Dr.Hess]

The copper pipe is part of the antenna.

[Douglas L]

No coaxial feed was used.

The main and reserve antennas can each be thought of as end fed wires, resonated by a tuner and worked against the ship’s hull as ground, with, of course, the surrounding saltwater improving ground conductivity and efficiency.

End fed wire antennas are often used by radio amateurs these days. It’s a way of getting an antenna up with just one support on the far end.

Disadvantage? Feeding a wire antenna at the end point generally means feeding it at a high voltage/ high impedance point. This can often cause excessive RF energy to float around the shack. However this was rarely a problem aboard ship due to the excellent ground.

Tankers often had a long wire end fed antenna that ran from the top of the wheelhouse or radar mast all the way to a mast on the bow. They were quite efficient.

 However the necessity of keeping the main deck clear on a container ship meant that end fed vertical whip antennas were used.

Since they were short compared to the operating frequency they weren’t as efficient.

  On U.S. flag ships the whips were generally an 18 to 35 ft whip made by Shakespeare.

  The whip antennas also had a serious disadvantage. During heavy seas their ceramic base insulators would get coated with salt residue, effectively shorting them out. I spent many an hour washing them down with fresh water, trying to get the transmitter RF current back to normal.

73,

Doug/WA1TUT 

ex ROU MREO 1978 to 1998.

On Feb 5, 2024, at 8:26 PM, Radio KH6O <radio...@gmail.com> wrote:



So is each copper pipe acting as part of the wire antenna, or is there an inner conductor within that pipe so that the innerconductor and pipe together are working as a coaxial feed?

On Sun, Feb 4, 2024 at 7:41 PM D.J.J. Ring, Jr. <n1...@arrl.net> wrote:

What you are seeing is two separate feeders made of copper pipe.

Ships were required to have a minimum of two antennas: a Main antenna and a Reserve antenna.

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[D.J.J. Ring, Jr.]

Feeders and Feedlines are both conductors that serve to conduct radio frequency energy from the source of generation (transmitter) to the radiating system (antenna). 

Feedlines are parallel Feeders. Balanced Feedlines are balanced conductors from the transmitter that are out of phase with respect to each other and carry equal currents. Because they are balanced and equal in amplitude they effectively cancel radiation at right angles to the plane of the direction of the conductors which minimizes unwanted feedline radiation. Feeders are generally rigid copper pipe and feedlines are generally flexible stranded wires separated uniformly by insulators. They both are types of transmission lines single feeders being the earliest and most primitive. Adding another feeder conductor in parallel to a single feeder markedly improves the radiation efficiency by simply reducing radiation from the feedline.

A feeder is simply a conductor between the transmitter and the antenna system. It is unbalanced and relies on the earthing (ground) return path to be effective.

A typical feeder is a system of rigid copper pipes held off the overhead of the ship radio station which are conducted through bulkhead feedthrough insulators to the outside of the ship to the "Non Conducting Antenna Trunk" which stands around 10 feet tall off the ship's deck. The Antenna Trunkwhich is the primary radiator of a typical medium frequency antenna as the lengths of heavy antenna connected to it at the top only serve as "top loading" like the top section of a Marconi Inverted L antenna.

73 

David Ring N1EA 

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[Better men make a better world]

Hello Jeff,

I only ever saw a single wire either to a Marconi T or a LW

73 Gerald EI6DP (qrz.com/ei6dp)

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From: radio-o...@googlegroups.com <radio-o...@googlegroups.com> on behalf of Radio KH6O <radio...@gmail.com>
Sent: 05 February 2024 03:07
To: radio-officers <radio-o...@googlegroups.com>
Subject: [Radio Officers, &c] Feedline aboard ships

 

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[D.J.J. Ring, Jr.]

True, but inside that single wire became a copper pipe insulated from the overhead, and bulkhead. The transition from wire to pipe occurred at the antenna trunk which was a structure about 10 feet (3 meters) tall with insulated connections at the top that the wires connected to. Inside were insulated copper pipes that led through feed through insulators through the deck and made it's way to the Radio Room and continued by copper pipe with standoff insulators on the overhead.

There were at least two sets of copper pipes, one for the Main Medium Frequency antenna and one for the Reserve Medium Frequency antenna. If HF antennas were fed with wire and not coaxial feeders, there would be more copper pipes for those antennas.

73

DR

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[Mike Hutchins]

Hello Jeff....maybe not always, but as a general rule, the reason for the 2 copper 'pipes' in parallel, was that one  'pipe' went to the main antenna and the second 'pipe' went to the emergency antenna.  Both through either deckhead or bulkhead via feed-throughs.

73....Mike.

O