Homebrew 20m loaded whip used for WSPR

 

Homebrew 20m loaded whip used for WSPR

20m Whip


Some years ago I saw some short fishing poles about 2 meters long in a pound shop. As fishing poles they were of little interest to me but I bought four as potential building blocks of antennas.

When M0XDK told me about Weak Signal Propagation Reporter Network and the minimal equipment requirements for worldwide coverage I realised this was something I could do from my holiday caravan and even the new DigitalHam Towers which has very little space for any HF antenna at all.

I constructed two homebrew loaded whips using the poles, some insulated wire bought years ago, heat shrink, and self amalgamating tape. There was no real design and no way I could give reproducable instructions for others to construct this antenna but the broad outline of what I did below, examination of the picture, and an antenna analyzer should provide a start point for others.




I took a glass fibre pole and used heat shrink of different guages to ensure it remained fully extended.
I took 7m of wire and after fixing the top with another length of heat shrink I formed a loose spiral the length of the rod to within about 50cm of the bottom where I then wound a tight simple coil.
At home I ran two 5m lengths of wire horizontally from the mounting point about 3m up at the edge of a sloping roof.
At the van I ran a length of braid from a roof screw to a gutter screw and on to a joining block near the antenna mount.
Using my MFJ antenna analyser I then adjusted the number of turns on the bottom coil to achieve as near a match at the low end of the 20m band that I could. At home this was very close to 1:1 but at the van the nearest I could achieve was ~ 1.6:1
I joined the coax to the whip wire and groundplane by soldering at home and using a juntion block at the van. Self amalgamating tape will hopefully keep moisture out.

In practice the antenna on the van works better than the one at home. This is either because the entire van is acting as a groundplane or the proximity to the sea. Maybe both.