Most of my experiments are with antennas end fed against ground in my back garden. The ground system is vitally important to antenna efficiency. Having read all the usual texts I have incorporated:
- 20 random length insulated copper wire radials, cut to fit the spaces available, slit into the grass.
- 4 copper/steel earth rods around the base of the automatic ATU, together with some 6 square metres of earth mat made of galvanised steel chicken wire.
- The above are connected to the ATU with a copper strap some 70sq mm in section, made up from paralled household power cables. This is about 1.5m long.
- Single counterpoise for all bands 160m to 15m and double counterpoises for 12m and 10m connected direct to the ATU and running in bushes along a fence about 1m high.
A professional gas-filled lightning arrester is fitted at the connection for the co-ax feed to the house, with a short strap to the ATU ground cable. Static charges are bled away with a small wax impregnated RF choke directly across the co-ax connector.
Any RF on the co-ax braid due to antenna imbalance or direct pick-up is stripped off by two professional external grade chokes just before the ATU connector and a home wound coil of feeder plus a 10m length of buried feeder nearer the house. The control cables are similarly choked and part buried. I also use a coil of co-ax feeder just after it enters the house, and have no measurable “RF in the shack” from these cables.
Although not optimum this system seems to produce quite good results, but I’ve had some maintenance issues over the years:
- Daughters pet rabbit chewing through the feeder
- Chopping the feeder with a spade while digging over the flower beds (by me!)
- Wild animal snapping control cables while digging for grubs or whatever
- Dodgy radial connections – seems to be soil acids eating into the conductors where they are exposed
- Broken counterpoises, mainly because the wire is a bit thin so it’s not visible…
All part of the fun!
I keep a record of relative earth currents at the ATU, and that enables me to tell if something has failed.