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©2018 F. Dörenberg, unless stated otherwise. All rights reserved worldwide. No part of this publication may be used without permission from the author.


Latest page update: 23 December 2018


under construction

INTRODUCTION


To be covered:

  • Background, my local conditions, why I "need" a telescopic mast, height of interest, to be used with which antennas (dipole, large STL, small STL,...).

THE GEROH 6M (20 FT) MAST


general (German army surplus, 5 sections, cable, hand crank), photo of collapsed mast, construction cross-section, accessories, geroh clamps, top hole, adapter stub for STL, adapter stub for rotor, adapter stub for dipole.

Bundeswehr, THW, ....

Model: "6 Klp/F AKAC019"

Early 1960s - 1990s.

Collapsed height: ca. 1.67 m (≈ 5.5 ft); Fully extended height: ca. 5.9 m (≈ 19.4 ft); Weight: ca. 18 kg (≈ 39.8 lbs); number of sections: 5; weight of accesories pouch: ca. 12 kg (≈ 26.5 lbs); outer diameter of base tube section: 88 mm (≈3.5 inch); max antenna weight: 15 kg (≈ 33 lbs); max wind speed: 100 km/h (≈ 62 mph); max wind load: 100 N.


gehro 6m mast

Sides of the Geroh 6 meter mast


gehro 6m mast

Geroh 6 meter mast - partially extended


gehro 6m mast

Bottom and top view of the Geroh 6 meter mast


gehro 6m mast

Label on my Geroh 6 meter mast


gehro 6m mast

Content of the accessories pouch of the Geroh 6 meter mast (hammer not shown)

(source: this 2010 thread in the "Allrad-LKW-Gemeinschaft" forum)


gehro 6m mast

Table of hand-crank revolutions vs. height of the mast top and vice versa

(source and printable sheet: see ref. 5)



ADAPTER STUBS

Mast accessories bag includes an insert, See top-left in accessories photo above.; dimensions of insert, size/depth of hole in top of mast + securing bolt.

 Need insert stubs for large STL, small STL, rotary dipole.

Large STL: 3-part; 59mm OD Alu rod (for 63mm OD PVC tube mast of STL) + steel washer + 26mm OD Alu rod , 12mm thread in rods for steel threaded rod. Alu because of weight, cost, ease of machining. Standard off-the-shelf diameters where possible, to reduce/avoid machining.

Small STL: 2-part: 40mm OD Alu rod (for 42mm OD PVC tube mast of STL) + 26 mm OD Alu rod, 12mm thread in rods for steel threaded rod.

Rotary dipole: top mast of rotator limited to 1.75", 35mm OD POM rod (OTS diameter) + 26 mm POM rod , 12mm thread in rods for steel threaded rod.  Until I get the rotator: 2-part insert.

Insert design drawing

gehro 6m mast adapters

Design drawing for two of the adapters that I need


gehro 6m mast adapters

Parts for the aluminum and POM/acetal/delrin mast adapter inserts


gehro 6m mast adapters

Aluminum mast adapter inserts




GUYING THE MAST



Diagram from manual + own diagram.

gehro 6m mast guying

Guying instructions

(source: ref. 3)

At two levels: largest/lowest diam mast section (1m15), top of mast (vriable, with max of 6m). Three directions, 120° apart.

My terrace no lawn --> no spikes. Eyebolt anchors in walls + very solid pergola post.

List of materials (2 eyebolt anchors, 36 m double-braided 5mm special polyester rope (Dyneema) with low elasticity/stretching  (1.5%) and high  tensile ( = breaking) strength (when new) 1100 daN ≈ 1100 kg equivalent 100 kg guying), 9 carabiners, 6 Camcleat® line-locks). In my case: not permament installation, so UV resistance is secondary. Boat supply store.

gehro 6m mast guying

Parts & material for guying the mast at two levels - rope, carabiners, cleats, eyebolt wall anchors

Photos of guyed mast



STOWING THE MAST


For stowing the mast, I use a single bracket. Two such brackets are/were used to mount the mast against the back of an army radio truck.

gehro 6m mast

Several views of the standard "Mastschelle" mounting brackets for this mast


gehro 6m mast

My mast - stowed upright against one of the walls of my terrace



REFERENCES



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