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Multiband End Fed Half Wave EFHW Antenna

This resonant End-Fed Half Wave (EFHW Version 2) 40 metre antenna was originally designed for portable field-day application and was instead setup in a permanent location at my QTH.

The first version was for QRP work. DOH! Had the antenna switch in the wrong position and burned up the ferrite core using 100W during a rag chew.

This time, I might of over-engineered it a bit, to handle 100W+ PLUS. The transformer now uses 2 (two) FT-140-43 cores stuck together with a few drops of Gorilla Super Glue. Polyamideimide magnet wire 18 gauge. Primary turns 2 to 15 secondary turns. 100 pF. / 3 kV. Capacitor across the primary. The impedance ratio is an in-between value of 56.25:1. Some people use 49:1 or 64:1.

How "The Weirdness" Shaped My Expectations of this Weird Antenna

When I modelled Version 1 of the EFHW, it was simply a slopped wire in free space. EZNEC showed really nice low SWR resonant points on three bands.

Now the Weirdness ...

To install the antenna a 66 foot wire in a 45 foot lot I bent the wire into a flattened 'U' shape with the middle of the wire running 4 feet over the roof.

I did some tests with my noise bridge to see where the antenna resonates. I found a dip around 6.8 MHz. OK, my antenna is too long, so I started to shorten it by folding back the end.

The 6.8 MHz dip didn't move...??? Back to the drawing board.

I measured all the aluminum eve troughs on both stories of the house and then proceeded to model them in EZNEC. WOW, there's a resonance at 6.9 MHz. COOL. Seems the lower eves is just about half wave on 40 metres. I need to see how much power is going straight up into space.

Three bands with no antenna tuner.

Second Weirdness ...

Tuning 80 metres, I found the signals very good. Ah, what the heck, flip on the tuner. It happily found a match in the middle of the 80 metre phone band. WHAT! MY field strength meter showed RF output. Back to the model.

This time I added the coax shield back the the shack as a counterpoise. Sure enough, the 80 metre resonance shows up in EZNEC.

This RF beast is sure hard to tame. I think I'll try to model the eve toughs as antennas to see what happens, I'll get back to you with the results. I don't think the eves will be a very good antenna, besides my XYL might balk at me when I cut a section out to shorten for 40 metres.

Oh, the antenna also tunes up on 30, 17 and 10 metres. 12 metre band a no go.

Metre Band - Tuner Function
80 - Tuner On
60 - NO OPERATION - TS-680 
40 - No Tuner
30 - Tuner On
20 - No Tuner
17 - Tuner On
15 - No Tuner
12 - NO MATCH, high SWR
10 - Tuner On