Getting ready for the top band in amateur radio

160m was the lowest radio frequency band allocated to radio amateurs before the adoption 630m and 2200m bands by many countries in the beginning of 21st century. It has been popularly called as the Top Band, may be because it is on top of the medium wave broadcast frequencies. 160m band has also been nicknamed the “Gentleman’s Band”! It is actually a medium frequency band if you go by the definition of 300 kHz to 3 MHz for medium frequency. Allocation in the 160 meter band for radio amateurs in India according to the National Frequency Allocation Plan 2022 is 1 800-1 825 kHz. In some other regions, allocation is given up to 2000 kHz. 

I have absolutely no space for a half wave dipole antenna for 160m. Hence I thought of a loaded coil dipole with 121 microhenries on each side. I used the online calculator to find dimensions. Antenna length before the coil was calculated as 12.5m and that after the coil as 7.5m on each side.

Soldered the joints to coils one by one. There were two joints to be soldered on either side of each coil. I did not solder the feedpoint as I am planning to homebrew and attach a voltage balun later.

After a lot of effort the coils and antenna elements are ready. I am using 15m of RG213 cable as feedline. The feedpoint region was then mounted at 5.5m from ground, on a galvanized iron pipe using nylon rope.

After mounting, the rather heavy loading coils were supported using additional nylon wires to prevent the antenna from sagging too much. One end of the antenna was at 3m and the other end at 2m from ground, due to mounting constraints at my home.

Testing the loaded coil dipole with NanoVNA

Earlier I used to test the SWR on various bands using my radio and or SWR meter. Now that I have a NanoVNA, I prefer to use it first. Moreover it gives more information than just the SWR. Currently I use the Smith chart in NanoVNA to decide whether my antenna elements have to be shortened or lengthened.