14MHz, 50cm tall antenna takes shape.

Following on from a very successful trial of a 50cm tall, 28MHz antenna recently, I moved on to 14MHz, where it may be easier to get a 1W signal further, and more consistently, than on the upper band.

The coil for this, based on a 50mm diameter PVC tube, is about 24cm long, with somewhere around 43 turns needed for resonance.  I guessed it might take slightly fewer turns, but I ended-up slightly short in the end, hitting 14.8MHz.

The early rule suggested by PE4BAS for the '50cm antenna challenge' is that the radiator, including the physical length of the coil (not the wire length in the coil), must be 50cm or less.  Radials were envisaged as being permissible (some might say 'essential'!)

Three questions then arose: 

(1) With such a short antenna, are the radials likely to become part of, or even the main, radiating component?

(3)  Should radials be allowed to be full length, or also limited to a maximum of 50cm?

(2) Should radials be disallowed?

I haven't had time to look at my radials and any radiation that may occur from them yet.  I suspect I may well find radiation when I come to examine them properly.

So, for my 14MHz build, I disposed of the radials, and connected the coax sheath to a copper tube ground connection instead.  Without any attempt to perfect things at all, I was already at a SWR of about 2:1 at 14.8MHz.  

I expect that, with a further few coils added to bring the resonance down to the bottom of the 14MHz band, and perhaps a shunt coil across the feedpoint (if needed), then it will be down to a good match and ready for tests.

Of course, soil conditions will mean adjustment of the antenna will very likely be needed from site to site, and even day to day, according to weather.  Usually, this is adequately achieved by a small adjustment of feedpoint height above ground.

More to come, as soon as I have good weather to do the tests, and I've seen the film 'Dune'!