30m Shortened vertical, updated.

Work continues between other duties on the shortened 30m vertical, just 5m tall.

I'm still working in the garden on this one, where there is too much clutter to get reliable results.  Nevertheless, I do now have a shortened 30m vertical that has excellent matching and performance.

To achieve this, I needed to swap the original coil for another I used a couple of years ago for other experiments.  This has a variable tap, and I found only ~7 turns were needed on 50mm pipe to reach the best match.  

The 'best match' was still 1.3:1, which is what you get with a standard 1/4 wave vertical fed with 50 Ohm cable.  You can either live with the 1.3:1, or try a second coil across the vertical and radial connections, which I found lowered the match to 1.13:1.

Here's the latest prototype, which of course needs a bit of tidying up for the final version:

Coil party!  It looks horrendously lossy, but seems not to be.

I know what you're thinking: 'wow, that looks like a lossy mess!'  I couldn't agree more.  But it works.  Here's the comparison with G0PKT, a full 1/4 wave vertical at 10MHz, which is at the coast in the east of England, benefiting from considerable coastal gain that we know from plenty of experiments here is typically 8-10dB:

Compared to a full vertical and its 'free' environmental gain at the coast, my 'coil wonder' seems to be working just fine.

Comparing to a typical doublet with 300 Ohm feeder, my antenna is doing very well indeed:

 

Nearly 5dB better than a doublet across all distances.

But out at DX distances, my antenna is 11dB better than the doublet.