HF End Fed Antennas
Recently, there has been a lot of enthusiasm for end fed antennas. It's easy to mount them in a horizontal, vertical, or other configuration. A transformer, or other means of matching to 50 ohm cable is required. For my experiments, I acquired a Balun Designs 49:1 unun, model 49131: https://www.balundesigns.com/model-49131-49-1-80-10m-efhw-up-to-1kw/. This is an excellent unit-- it is built like a tank and can handle up to 1 kW ICAS, including FT8 digital operation with a 50% duty cycle.
I also tested a Par EndFedz Model 10H antenna (for 10 meters). I tried using a 20M half wavelength long wire on the EndFedz 10H transformer, and indeed it exhibits a good match on both the low end of 20M and also at about 28.400 on 10M. As expected, the harmonic resonance is a bit higher in frequency. I think it could also be configured as a 40-10 or even 80-10M end-fed antenna by using an appropriate length of wire, although it would benefit from the addition of a small loading coil for those configurations to move the higher harmonics lower in frequency.
For my tests, I hung the antenna from a tree at about 55'. Although it exhibits an excellent match, performance on 10M does not come anywhere close to my 3 element beam mounted at a similar height. The same was true of the original (10M half wave) configuration. The ambient noise level was also several S-units higher. I added a choke at about 5' below the transformer, and that dropped the noise by two S-units. It is now S-0 on 10M and about S-3 on 20M. The choke consists of 6 turns of DX Engineering RG-8X cable around an FT-240-43 toroid. On 20M, the antenna works quite well and seems comparable to a half wave horizontal dipole at about the same height. Looking at the spectrum display on an IC-7300 on the 20M FT-8 frequency, some signals are stronger on the vertical and some are stronger on the horizontal antenna, as would be expected.
The 10H lacks one convenience that the Balun Designs transformer offers; a separate terminal for the attachment of a short counterpoise wire. This is easily remedied by clamping the wire to the shell of the antenna connector, or else by using a short length of coax between the antenna and line isolating choke, which is what I did.
I think this antenna will find more use as a portable antenna for "ham in the park" type operations than as a permanent part of my home station. Together with a set of wires cut for various bands, it can quickly and easily be configured for use on a desired band. A useful set might include a wire cut to 1/2 wavelength on 40M (with compensating coil) for use on 40-10M, a wire cut to 1/2 wavelength on 20M for use on 20-10M, and perhaps a wire cut to 1/2 wavelength on 17M.
I also tested a Par EndFedz Model 10H antenna (for 10 meters). I tried using a 20M half wavelength long wire on the EndFedz 10H transformer, and indeed it exhibits a good match on both the low end of 20M and also at about 28.400 on 10M. As expected, the harmonic resonance is a bit higher in frequency. I think it could also be configured as a 40-10 or even 80-10M end-fed antenna by using an appropriate length of wire, although it would benefit from the addition of a small loading coil for those configurations to move the higher harmonics lower in frequency.
For my tests, I hung the antenna from a tree at about 55'. Although it exhibits an excellent match, performance on 10M does not come anywhere close to my 3 element beam mounted at a similar height. The same was true of the original (10M half wave) configuration. The ambient noise level was also several S-units higher. I added a choke at about 5' below the transformer, and that dropped the noise by two S-units. It is now S-0 on 10M and about S-3 on 20M. The choke consists of 6 turns of DX Engineering RG-8X cable around an FT-240-43 toroid. On 20M, the antenna works quite well and seems comparable to a half wave horizontal dipole at about the same height. Looking at the spectrum display on an IC-7300 on the 20M FT-8 frequency, some signals are stronger on the vertical and some are stronger on the horizontal antenna, as would be expected.
The 10H lacks one convenience that the Balun Designs transformer offers; a separate terminal for the attachment of a short counterpoise wire. This is easily remedied by clamping the wire to the shell of the antenna connector, or else by using a short length of coax between the antenna and line isolating choke, which is what I did.
I think this antenna will find more use as a portable antenna for "ham in the park" type operations than as a permanent part of my home station. Together with a set of wires cut for various bands, it can quickly and easily be configured for use on a desired band. A useful set might include a wire cut to 1/2 wavelength on 40M (with compensating coil) for use on 40-10M, a wire cut to 1/2 wavelength on 20M for use on 20-10M, and perhaps a wire cut to 1/2 wavelength on 17M.