Quick End Fed Half Wave for 20/15/12/10 metres

This antenna was put together very quickly for an overseas trip, but it worked out quite well.  The End Fed Half Wave (EFHW) for 20/15/12/10 metres uses common automotive bullet connectors for linked bands and RC servo horns for the insulators.  The whole thing is wrapped on a SOTABeams winder.

All wrapped up

Servo Arms

The bullet connectors are not the best (high insertion force and crimp), but they work and I had them already.

Links

Longer  term I will replace them with RC gold plated bullet connectors or switches.  The antenna wire will be replaced with ultra light wire.

As radio controlled modelling is another hobby, I have heaps of RC servo arms left over from servos.  These arms have several holes either side of the servo shaft mount and make good insulators.  They are also pretty compact and don’t make the whole thing bulky when wound up on the winder.

The arms were trimmed down with side cutters so that they had only 2 holes each side of them.

 

The finished measurements for my EFHW were:

Matcher> < 5140 mm > Link A < 960 mm > Link B <1020 mm > Link C < 3530 mm >

Link A+B+C is for 20m tuned to 14.26 MHz

Link A+B is for 15m tuned to 21.2 MHz

Link A is for 12m tuned to 24.965 MHz

No link is for 10m tuned to 28.5 MHz

If replicating this design, I would recommend starting with at least 100m longer on each section of wire and trimming down as required.  The matcher used is described here and note that it uses 17 turns tapped on a T106-2 core as described at the end of the article for 10m operation.

I started with the 10 metre section first, tuned it and then added the 12 metre section next and tuned it and so on.  The added sections did not seem to detune the previous sections to any noticeable amount.  To reduce the length of each section while tuning, I just bent the wire back on itself about 25mm at a time with a loose knot.  Once the final length was tuned, it was cut and knoted to the servo arm.  A 3 metre length of wire was added to the end after another insulator for tying it off.

As for any EFHW, it doesn’t need much of a ground due to the high impedance, although if you don’t run a metre or so of ground, the return path will be through the radio and mic etc.  and may cause problems.  I haven’t noticed any bad effects from this in the past, but there may well be problems with some rigs, so best to run a ground wire of about 2 metres.

In the field, a 4.5 metre squid pole keeps the EFHW supported in an inverted V configuration.