Here is a proto type telescoping mast. It appears to be a well engineered all aluminum structure that telescopes from 47" retracted to 84" extended. This item has an amazing attention to detail, the workmanship is perfect. It is powered up by the winch and lowers itsefy by gravity. I think this company built these up to 40 feet or so.
The square tubing is 5"-4"-3" and 2". The item "ALUMINUM TELESCOPING MAST" is in sale since Sunday, January 22, 2017. This item is in the category "Consumer Electronics\Radio Communication\Antennas\Ham, Amateur Radio Antennas". The seller is "halfway270" and is located in Parachute, Colorado. This item can be shipped to United States, to Canada, to United Kingdom, DK, RO, SK, BG, CZ, FI, HU, LV, LT, MT, EE, to Australia, GR, PT, CY, SI, to Japan, to China, SE, KR, ID, to Taiwan, ZA, TH, to Belgium, to France, to Hong Kong, to Ireland, to Netherlands, PL, to Spain, to Italy, to Germany, to Austria, IL, to Mexico, to New Zealand, SG, to Switzerland, NO, SA, UA, AE, QA, KW, BH, HR, BR, CO, PA, JM.