- [The Geroh 6m (20 ft) mast]
- [Adapter stubs]
- [Guying the mast]
- [Stowing the mast]
©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
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.
Sides of the Geroh 6 meter mast
Geroh 6 meter mast - partially extended
Bottom and top view of the Geroh 6 meter mast
Label on my Geroh 6 meter 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)
Table of hand-crank revolutions vs. height of the mast top and vice versa
(source and printable sheet: see ref. 5)
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
Design drawing for two of the adapters that I need
Parts for the aluminum and POM/acetal/delrin mast adapter inserts
Aluminum mast adapter inserts
GUYING THE MAST
Diagram from manual + own diagram.
(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.
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.
Several views of the standard "Mastschelle" mounting brackets for this mast
My mast - stowed upright against one of the walls of my terrace
- Ref. 1: "Betriebsanleitung Mast Typ 6 Klp/F AKAC019" [operating & maintenance instructions], Geroh G.m.b.H., 1999, 17 pp.
- Ref. 2: "Seilzug Teleskop-Kurbelmast Typ 6 Klp/F", Geroh Apparatebau, 10 pp.
- Ref. 3: "Beschreibung des Seilzuges" [description of cable pull mechanism], Geroh G.m.b.H., 1963/1972/1993, 10 pp.
- Ref. 4: "Technische Dienstvorschrift für Antennenmast 6 m mit Sicherheitshandkurbel und Zubehör", TDv 5985/002-13 (25 pp), TDv 5985/002-15 (October 2005, ca. 225 pp.)
- section 1.4 "Zubehör und Vorrat" [accessories & supplies]
- Ref. 5: "Geroh 6m mast - table of hand-crank revs vs. height of mast top"; source original table: this thread in amateurtele.com forum.