Monday, December 12, 2016

Military Antenna Masts Part 5, AB155A/U

After working a few Field Day operations with local clubs I decided to get a few masts of my own.  I started with the LCSS support poles shown on the mast information page and while searching the web for information on them I found references to the MS-44 mast sections.  Later I found they were part of the AB-155/U mast that was issued with the AN/GRC-26 Radio Set.  Apparently these mast sets as well as the AN/GRC-26 were issued is several series.  I found reference to the AB-155, AB-155A/U and AB-155B/U.  They all seem the same except for the issue quantity of some of the hardware.  I have 2 different MS-44 mast sections.  I have 2 sets made from steel and several sets made of aluminum.  I managed to find several sets of un-issued surplus MS-44 sections made in 1982 or newer and tagged in 2004.
Here is the website I found one of the manuals:
               TM 11-5820-256-20      
               TM 11-5820-256-24P
The following is issued with the AN/GRC-26 
5985-507-6261         6         Mast, AB-155/U, AB-155A, B/U
Each of the following is issued with each AB-155*/U listed by FSN, Quantity Required, Quantity Issued and Item.
5920-497-8634         1         1         Carrying Device MX-387/GRA4: SC-D-28057                                                                                                                                                  
5820-221-1563         1         1         Cover CW-124/GRA4: SC-D-28056                                                                                                                                                              
5325-497-8640         4         4         Guy Fastener MX-379/U: SC-D-28050                                                                                                                                                            
5820-224-4638         3         3         Guy Plate MX-378/U: SC-B-28049                                                                                                                                                   
5975-503-0702         4         4         Guy MX-381A/GRA4: SC-D-28053                                                                                                                                               
5975-538-0199         4         4         Guy MX-382A/GRA-4: SC-D-28053                                                                                                                                               
5975-503-0733         4         4         Guy MX-383A/GRA4: SC-D-28053                                                                                                                                               
5985-228-8064         1         1         Halyard MX-516A/GRA-4: SC-D-28054                                                                                                                                           
5120-203-4656         1         1         Hammer, engineers, Double Face 2 1/2 lb; GGG-H-86, Type X, Class 1                                                                                           
5820-240-8233         1         1         Mast Base AB-154/U: SC-DL-182925                                                                                                                                           
5985-636-2420         1         1         Plate, Mast Base: SC-B-84299                                                                                                                                                           
5820-227-7168         8         8         Mast Section MS-44: SC-D-1155                                                                                                                                                       
4030-187-5263         4         4         Guy Stake; Metal; 18 1/4 in. lg: SC-DL-33399                                                                                                                               
5510-187-5267         4         4         Stake, Wood; 1 1/2 in. dia X 30 in. Ig.: SC-C-22005                                                                                                                                        
5985-453-9439         1         1         Tripod Adapter Mast AB-1089( )/U: DL-SC-B.459357

This is an old issue AB-155/U.  As seen from the photo the issue quantity has changed as well as the design of the guy fasteners and base plate. I have one of these complete.  I also have others that I am still assembling. 
The military states using these at 40 feet.  I am working on making at least 2 sets that will be 50 feet.  Plans are to use 1/4 inch diameter dacron rope rather than 3/16 inch and adding at least one level of guys.
Keeping the standard 40 feet AB-155/U and adding 2 sections the top could be guyed which would require only one additional set of special length guy ropes rather than changing the overall guying and making custom lengths for the 50 ft. masts.

The 1089 tripod adapter is shown below:

 This is one I bought from a surplus dealer on Ebay and repainted.  I have several of these and all are modified.  The originals were made of steel as best I can determine.  They were welded and tack-welded.  The next series was either as shown above or epoxy fastened center with the same crimped leg receiver tubes.  The epoxy ones are painted with gloss olive drab paint and the center tube can break loose.  I found one on another site that showed an original and it was like mine (made with epoxy) that I took apart and welded.  Also notice on the above photos the center tube isn't welded to the top plate. 
 The steel AB-1089/U.  The center tube is welded at the bottom and under the top plate.  The leg receiver tubes are welded to the plates. See figure 2-17 on page 53 of the pdf file for the AB-155/U.  Link is at the bottom of the page.