The Backyard 160m RX Reference Vertical
Building the vertical partThis consists of 6mtr black polyurethane coated copper clad steel wire (0.9mm dia.), taped to a 6mtr glasfiber pole. At some point we collected 6 pcs of these cheap fishing poles near the end of a fishing season in a large store. Currently they are all in use and we're gonna need more of them.Ground connectionWe hammer-drilled a 2mtr, 22mm dia. copper pipe into the ground. From earlier experiences we already knew that there are small ‘seasonal’ changes in the earth resistance. Not alarming though, but since this is going to be a reference antenna we added 4 radials. These consist of 4mtr blank copper wire, 1.5mm dia. which are buried at 10cm depth in the ground and connected to the copper pipe. Measurements during the year on a network analyzer showed that this ground setup remained constant.Bringing the 6mtr (20 ft) rod to resonance on 1830 KHzAfter several experiments with various coils on different types of toroids, we found that about 38 windings on a FT114-61 ferrite in series with the vertical wire works well. Resonance is pretty sharp though; one extra turn will shift it some 20 KHz. Impedance showed near 50 Ohms, but that's just stupid luck, otherwise we would have added a series loading resistor or a suitable x-former.What else?The waterproof box also holds a 1:1 transformer which consists of 2 by 2 turns of generic insulated hookup wire on a type #73 binocular ferrite. The coax is wound several times on a FT150-J (1500mu) toroid to minimize unwanted common mode noise. Burying the coax in the ground helps too. At the receiver input a similar common mode coax filter is used.
