EARCHI antenna

The antenna I used for portable operation  last year was the BuddiPole of friend and fellow radio operator Mike, AB9ON. BuddiPoles clearly work but I wanted to build some wire antennas in order to have some additional options. The first antenna on the list is the EARCHI End Fed 6–40 meter multiband HF antenna. The EARC club used to sell kits but they don’t anymore however the instructions are on their site here and it’s certainly not a difficult antenna to build.

The first thing that you need to do is to build the 9:1 matching transformer. It is built on a T130-2 toroid.

T130-2 Toroid

T130-2 Toroid

The instructions are plenty clear as to how to wind the transformer.

Winding complete

Winding complete

Transformer complete

Transformer complete

For the enclosure I choose a Hammond 1591B. It’s nice and small and I like the transparent blue but the side walls are a bit short so you will need to use a bulkhead chassis mount SO-239 instead of a flange chassis mount as there isn’t enough room to mount the latter.

Installed in project box with connectors

Installed in project box with connectors

Once the matchbox was completed I tested it with my MFJ-259B. I soldered some resistors in series to get 450Ω (in this case 491Ω) with the expectation of seeing around 50Ω through the frequency range.

Testing with MFJ-259B

Testing with MFJ-259B

Results were as follows:

Test results

Test results

 

Frequency R Ω SWR
7.000 30 2.8
7.300 31 2.7
14.000 60 1.7
14.350 60 1.7
21.000 62 1.5
21.450 62 1.5
28.000 55 1.5
29.700 58 1.5
50.000 116 3.0
54.000 148 3.7

It stays around 50Ω through the intended frequency range with the exception of 6m but that’s OK. I have other antenna choices for 6m.

The next thing to do is to attach the antenna wire and try it out.

 

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