Globalstar Product Management – Technical Support

Globalstar GAT-17MR Maritime Antenna – Dimensions and Mounting

The Globalstar GAT-17MR Maritime Antenna uses a standard 1″-14 marine pipe thread.   This is the same thread asis used for the Globalstar Extreme Enclosure domes.

An engineering drawing for the GAT-17MR antenna is provided at the following link:

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Details of the Standard 1-inch 14 TPI Marine Pipe Thread:

The 1″-14 (1-inch diameter, 14 threads per inch) standard marine pipe thread is a straight thread, rather than a tapered thread, as is commonly used for plumbing.

The differences between NPT (tapered, for plumbing of liquids and gases) and NPS (a.k.a. NPSM) (straight thread, marine pipe thread) are described in the following link:

http://www.ehow.com/info_8723422_difference-between-npt-npsm.html

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The following images show the two types of pipe threads side by side, so they can be compared with each other:

Fitting NPT tapered pipe into NPS parallel female coupling Male NPS - Male NPT Adapter

 

Availability of Straight-Thread Pipe Fittings:

Straight-thread (a.k.a. marine thread) pipes and fittings are widely available.

  1. There are also a wide variety of adapters available, which have a marine pipe thread on one end and a different thread (e.g., NPT) on the other end.
  2. The installer should call some local shops to see if they have the appropriate fittings. Otherwise, the parts could be delivered promptly via an online supply shop.

Work-Arounds – If Straight-Thread Fittings cannot be found:

If an installer cannot get the necessary marine pipe thread fittings:

  1. We have found that threaded PVC pipe will usually mate acceptably with a marine pipe thread, probably because the PVC threads are more flexible than the threads of a steel pipe.
    • However, if a PVC pipe is attached to a satellite antenna mounting flange, we recommend keeping the length of the PVC pipe to a maximum of 4″.
    • This recommendation is based on the extreme environments (cold, wind, heat) experienced by satellite antennas, the lower strength of PVC relative to steel, and the increased susceptibility of PVC to becoming brittle with aging.
  2. If the PVC section is kept to 4 inches or less, it will usually last a long time without any problems.
  3. If a satellite antenna installation requires a longer pipe length than 4 inches:
    1. Use a 3″ or 4″ male-male PVC pipe to provide the connection between the GAT-17MR and a female-female NPT adapter (or whatever pipe thread standard that you want to use for the rest of the installation),
    2. The metal NPT adapter will provide a strong interface between the short PVC section and the rest of the downstream pipe sections.
  4. Depending on the installation, it may be necessary to use clamps and/or guide wires on long pipe sections, or to increase the diameter/rigidity of the NPT pipe downstream so that it will be structurally sound.

 

Additional Keywords:  maritme installation, extreme

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Written by Joseph Crowley

July 1, 2014 at 5:24 pm

Posted in Uncategorized

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