Thursday, 13 February 2020

Ham radio-Vertical aerials

Ham radio-Vertical aerials.

Ham radio-Vertical aerials.  Many people starting in Ham radio build a dipole for their first aerial, its simple to build using the 468 feet formulae to which you divide the frequency you intend to operate. To take an example of the above, say we wanted to work on the twenty-meter band which has a frequency of 14 Megahertz, 468 divided by 14 is approximately 33 feet, dipoles work very well, is sighted North-South they will radiate in an east-west direction if orientated and a half wave-length above ground you will get considerable gain at a low angle, Ideal for DX

The picture shows a DX Commander Lite Four band aerial-Click for his M0MCX and his vertical kits.

The picture M0MCX and his excellent vertical aerial kits.

33 feet above ground is quite a distance and for most urban dwellers it's out of the question when it comes to erecting your ham radio aerial, what can we do? If we desire to work longer distances than is possible on a low sited dipole, we can use a vertical aerial attached to a convenient post at ground level.

Over the years I have been interested in ham radio I have experimented with lots of designs for aerials to transmit my signal at a low angle to catch the elusive DX stations, which are often rare especially if they on a DX-pedition.  Check the RSGB for information

I have had tremendous success in building vertical aerials for HF bands and they have worked very well for me. A couple of pieces of timber bolted together to give you the height for attaching your radiating element work just fine, say you wanted a single band model for twenty meters, use the formulae for a quarter-wave aerial, its exactly half the number for a half-wave ie 234 feet, dividing this number by 14 Megahertz is about 16 and a half feet.

Attach the length of 16.5 feet copper wire on the wooden support, I use a short piece of aluminum tubing hammered into the soil to support the wooden mast, solder the center of your coax to this wire. Cut about 16 pieces of the same wire and length and solder them together and attach these to the braid of the coax with solder. If you can manage it lay these radial wires in a circle around the wooden mast on the ground. Use self-amalgamating tape to waterproof your connection.

A balun is not usually necessary however I ran my coax from a vertical near to house wiring which inevitably induced noise into the coax, this can be easily cured by using a balun, wind about 17 turns of your coax near to the bottom of the mast on a T-200 ferrite ring  Push the coax through the ring forming coils over the ferrite, so will notice a huge drop in noise doing this. I hope you find this useful.

Ham radio-Vertical aerials.