1. J or Slim Jim for 144MHz
The following aerial was built by Victor G1PKS:
The prototype aerial was cut exactly to size using 16swg enamelled copper wire on a one inch (25mm) square wooden support, no tuning adjustments were necessary to obtain less than 10% reflected power and the results on the club net were extremely good. A final version was made in 6mm copper pipe and mounted inside a capped plastic waste pipe to protect it from the weather.
The plastic tube does not appear to have any significant effect at RF and a piece remained cold after a session in the microwave oven. However, it did crack and break cleanly around the point of contact with the metal mast clamp after some 8-
2. Repairs to J-
This aerial is 30+ years old and although wearing fairly well the rear two elements had begun to weaken and the plastic cable housing eventually ceased to be waterproof -
I rebuilt the rear two elements from 8mm microbore fittings and purchased a waterproof plastic box and waterproof cable gland from a local electrical supplier to replace the original plastic housing. The rebuilt assembly was fairly easy to install in the new box and attach back on to the aerial. See below:
The new elements were given three coats of paint and the aerial reinstalled on the rotatable mast.