I wanted to use 160m while operating portable on the Remembrance Day Contest.
I realised that if I placed the right sized loading coil between the 40m and 80m link on the linked dipole, that I should be able to make it do 160m.
Thinking further, I decided that I’d make a seperate leg connected to the loading coils so I could tune the length for best resonance.
With some calculation I determined that I needed loading coils of 81-89µH and that winding 44 turns of 0.8mm wire on a 5cm diameter form would give me 85.6µH.
Wind the coils.
Put the electrical and the mechanical connectors on. Now it’s ready for a pair of 10m runs of hookup wire with spade connectors on.
The clip connects it to the 40m link of the dipole. One of these has a pole connector and the other a spade. On the other side I have a ring and a tent slider. I’ll tie off a 10m run of hookup wire on the ring and attach a spade connector to attach it to the coil.
Trying it out at Mt Bouddi
I made some 11m legs for it (so they would certainly too long) and took it with me to Mt Bouddi.
Unfortunately the coils add too much weight for the antenna to be hung from a squid pole. I’m going to have to rethink this.
- A couple of options spring to mind.Find a way to support the antenna at the point I place the coils. This cold be some light rope hanging from a tree, some shorter poles, or something like that.
- Look at light ways of getting 85 µH at that point in the antenna. Perhaps by winding something on a ferrite toroid? Does anyone know if I put a choke in of that inductance if that would have the same effect? I suspect I’d have to take in to account the current and voltage at that point in the antenna at about a quarter wavelength down a half wavelength leg at 1.85 MHz.