2021-12-07

This is very common W7IUV Flag Antenna you can find on many web sites. I mainly followed the PY3AGD design, Clovis from Brazil, because he uses the antenna mounted horizontally (see his videos on Youtube) and it was perfect for my small city lot installation.

As you can see in the picture below I mounted the antenna on the same pole of my HexBeam and I can rotate it when needed. The loop has some kind of directivity and it can be helpful rotating it on the right direction.

Overall size is quite small, about 2.3m x 4.6m (7.55ft x 15.1ft).

Below are some building details. I used a main 40x40mm aluminium boom and four VTR spreaders.

The very simple schematic is shown below. In my installation I am using a simple RG58 feed line so I used a 640 Ohm Termination Resistor.

640 / 50 = 12.8 so I can still use a 12 : 1 impedance transformer - (7 turns / 2 turns = 49 / 4 = 12.25) 

During the various tests I found the suggested pre-amplifier not so helpful. I tested several models but with each of them the noise raised up the same as the signal. So I removed the preamp and added an RF choke made of 8 RG-174 turns on a FT-140-43 toroid.

The result was striking: in this way I was able to eliminate almost all of the human electrical noise and in addition I relied on the superlative qualities of my Anan 7000-DLE that has an incredible audio recovery algorithm. You don't need a preamp, just trim the AGC level ultil you can hear the station well out of the noise. 

In this video I am listening to a Numbers Station and sometime I am switching to the End-Fed long wire transmitting antenna. During the listening I tried to beam the station rotating the loop and observing strengh signal variation.

73' Enzo
iw7dmh