Just to provide you an example, my 15m long antenna (Please refer to below), my antenna is providing me on 15m band an almost perfect SWR. My experience is to put more space between the turn at the secondary of the transformer. Too much inductance –> The transformer secondary is not correct and double check again. My experience is adding the minimum space to between the primary turns is providing great results You can also add less of more space between the turns. Too much capacitance -> Your transformer primary is not correct and check again. If not, you will need to check the transformer and with the analyzer to check the capacitance and inductance provided. You will need also a 2400 up to 2500 ohm non-inductive resistor connected to the output of the transformer and tap to the ground. If you do not check the transformer there is a high risk your antenna will provide you a good SWR but the antenna will be not resonnant and the Current/Voltage repartion along the antenna will provide a poor efficiency and radiation pattern.įor that you will need an antenna analyzer likely the NANO VNA or the SARK100 Antenna impedance for this antenna is roughly around 2500 Ohms and the transformer is providing the adjustment from the 50Ohm from your TRX to the a ENDFED monopole which is about 2500 Ohm from 3 up to 30Mhz. In any case you shall control the transformer prior to the final installation with the antenna. Since the transformer is inside the Attic, it is well protected against the rain and humidity This configuration is provided a great SWR in all bands and only on 80m the bandwidth is really narrow with about 40Khz. The Transformer is located inside the Attic just underneath a tile and only about 10cm of wire still inside the attic. This antenna using this kind of transformer is a compromise.ĭO NOT EXPECT FOR HIGH EFFICIENCY FROM 3Mhz up to 30Mhz ONLY WITH A SINGLE 1:49 or 1:64 TRANSFORMER.įor better efficiency, the FUCHS Transformer is by far a better choice : The performance are acceptable below 20m (14Mhz)due to high losses from the transformer during transmit for frequencies above 14Mhz.
I am using this antenna for almost 2 years and since i have limited space with my tiny garden. The total antenna lenght is about 23 meters, with one 20.4 meters long segment from the 1:49 transformer to the 110uh coil and about 2.2 meters long segment from the coil to the insulator. With this antenna the coverage is 80,40,20,15 and 10 meter band without any antenna tuner and the average SWR is below 1.2 on phone bands. My 1:49 Transformer is located in the Attic, just under a tile and obviously the wire is routed outside and hook on a 12 meters fiberglass pole in the garden.
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