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LINKS: TOWER TRAM ANTENNA VIEWS
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| The antenna is a new in the box KLM 3 element 40 M linear loaded Yagi. It has a 32 ft. 3 inch boom and 42 ft long elements. It was tuned for the middle portion of the 40 M band. SWRs are as follows: 1.8:1 at 7.000 Mhz falling rapidly to 1.5:1 at 7.010 then tapering down to 1:1 at 7.180 and finally rising back to 1.8:1 at 7.300. Performance has been phenomenal; I rarely need the amp these days! | |
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Prior to installation the TowerTalk reflector was queried as to modifications to be made to ensure long life. The following mods were performed: All split lockwashers/nuts were replaced with Nylok locknuts, all tubing joints were through bolted in addition to the hose clamp, the holes in the diamond shaped linear loading insulators were drilled out to prevent binding with the linear loading rods during windy conditions which may cause the insulators to break, heavy duty DX Engineering element to boom insulators were purchased, a large 18 in. by 24 in. boom to mast plate from DX Engineering replaced the supplied 8 x 10 plate (the new plate has 5 u-bolts securing it to the mast and 8 u-bolts along the boom for added support), and finally square fiberglass tubing from MaxGain Systems and dacron rope was used to lightly truss up the elements from the boom for snow loading on the elements. The stock balun and matching system was initially installed. |
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About two weeks after the installation, an intermittent developed in the system. Applying some power would cure it but soon it became permanent; high SWRs and the antenna was dead. Some experts had bad experience with the KLM impedance matching system, so a new 1:1 current balun and matching system was made and installed but to no avail. The feedline from the shack to the base of the tower checked out OK; all new coax was used during installation. Winter weather started to set it as well as operator depression! Finally a break in the weather allowed another trip up the tower to check out the connections on the driven element itself. Lucky this element it right at the tower and was able to be swiveled up and down to check all connections. All were found to be sound but they are really tight now. Still no luck. The final option before an anticipated long winter was to replace the coax that ran up the tower. This was done and voila! It now works like a champ. The problem? The PL259 connector at the top had a bad connection between the connector barrel and the coax shield. All the holes were filled but the solder never wicked down into the braid!?! Who woulda thunk?
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| An AlfaSpid worm gear rotator is turning the assembly. These rotators are really nice, worm gear torque for the cost of a Ham IV, no brakes to break, no end stops to jam on. End stops and presets (6) are electronically set. The controller has a large digital readout. (It's getting harder to see that fine print these days!) Powered with 12-24v DC; only four wires out to the rotator. |
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