My CG3000 remote tuner is currently sitting in the garage. Its replacement is a homebrew flowerpot antenna for the 17-metre band, assembled from RG58, a length of DX Commander wire and plenty of adhesive-lined heat-shrink.
It’s working very well indeed.
Built from what was available
I didn’t have a single piece of RG58 long enough for the job, so I joined two lengths together. The upper element uses DX Commander antenna wire, with the joints insulated and weatherproofed using adhesive-lined heat-shrink.
The coax coil is wound around a piece of 100mm PVC pipe. The antenna is supported by a 12-metre Spiderbeam pole, with the coil approximately one metre above ground.
Nothing particularly exotic—just materials I could put to use.
A calculator I keep coming back to
My starting dimensions came from the NOMONS Flower Pot Antenna Calculator, which I’ve used for several builds.
One feature I particularly like is that it gives the length of coax to use for the choke coil. I don’t have to enter a coil diameter first: I can wind that length onto the former I have available, and the number of turns follows from that.
That suits the way I build things. There’s usually a suitable bit of pipe somewhere.
I treat the result as a starting point for the actual antenna, though, rather than a guarantee that everything will be spot on first time.
Leave a little extra at the top
In my builds, the calculated dimensions haven’t produced exactly the SWR result I wanted without adjustment.
I usually find that the upper element needs to finish a few centimetres longer than the calculator suggests. That’s my experience with my materials and installations, rather than a correction I’d automatically apply to everyone else’s antenna.
My approach is to leave extra length, measure the antenna and adjust from there. Cutting wire off is straightforward. Putting it back is rather less elegant—even on an antenna that already contains two joined lengths of coax.
What happens on the air?
The encouraging part has been using it.
In my FT8 comparisons on 17 metres, the flowerpot has been doing better than my 80-metre EFHW, particularly for DX. That’s the practical result that has earned it its place on the pole.
These are observations from my station, rather than a measured gain figure. Propagation, activity and the particular stations available all influence the outcome. I’m comparing two complete installations in my garden, with their different geometries and compromises.
Nevertheless, the results have been encouraging enough that I’m very happy to keep using it.
A place on the pole
The CG3000 arrangement gave me the flexibility to work several bands and improved noticeably after I added radials. The flowerpot is a different proposition: this build is intended for 17 metres, and so far it’s doing that job very nicely.
There’s considerable satisfaction in getting good results from an antenna assembled out of spare coax, wire and a bit of pipe. Even more when the dimensions have been adjusted through your own measurements and the results hold your interest on the air.
The CG3000 hasn’t been condemned. It’s waiting for another experiment.
For now, the flowerpot has the job.
73,
Kev — M7XOM