Make an end-fed antenna for 80 metre operation

The physical length of any HF antenna is critical to achieve resonance and good performance on a particular band. Dipoles need to be half a wave length long, locating these long antennas can be an issue, especially when we are aiming for the 80 metre band or lower. 

However, we can reduce the space needed to a quarter wave length if we decide to use a end fed antenna. The end fed antenna is essentially half a dipole, it uses a good earth connection to complete the arraignment. 

Below is one example of how to build a 80 metre band long wire antenna for a house with a small garden. 

80 metre end-fed antenna design

Antenna 

To identify the correct length I used the fantastic Antenna design page created by Martin. E. Meserve: http://www.k7mem.com/Ant_End_Fed.html. For the 80 meter band, the ideal length is 21.9 metres. 

Feeder and UnUn

The antenna is fed by low loss coax into a 9:1 UnUn. One terminal of the UnUn is connected to a good ground and the other to  the antenna wire. The UnUn is located away from the house. Low loss coax is used due to the distance between the radio and the UnUn.

Grounding

I used a length of copper water pipe as the earth spike. A standard earth connector tab was used to make the connection. Counter poise radials can also be added to improve antenna performance.

You'll need an ATU (Antenna matching unit) with this type of UnUn

For this antenna to present a good match to your radio an ATU will be required. I used an Auto-ATU, however because this is an mono band design a simple manual tuner may be better. I found that my ATU was easily able to present a 1:1 match to my radio.

Parts list

  • 9:1 UnUn
  • 21.09 meters of antenna wire
  • Earth spike
  • Earth lead
  • Low loss feeder (terminated with connectors)
  • Antnna insulator
  • Para cord
  • Ring terminal crimps
  • ATU


Mounting the end-fed antenna using the roof of our house

To fit the antenna in to the room available the antenna wire (or at least the para cord supporting it) is strung over the roof of the house. This was achieved by attaching fishing line to a tennis ball and throwing this over the roof. Para cord was then attached, then the insulator and the antenna pulled over. This para cord was pulled taught and tied off on a cleat.

The UnUn is fixed to a pole at the furthest point from the house. The antenna wire is connected to the UnUn along with the earth connection and feeder coax.

40m loaded dipole design
40m loaded dipole design
Mounting the 80 metre end fed antenna
Mounting the 80 metre end fed antenna
End fed antenna 9:1 UnUn
End fed antenna 9:1 UnUn

Tuning and performance

With the use of an ATU a 1:1 match was easily achieved. The 80 metre performance was great, far better than trying to tune up a 40 dipole to work on 80. Also this antenna is quite, very quiet. This is probably due to the antenna being fed away from the house. Good news! 

 


Make it multi band

This antenna is currently only useful on 80 metres, but if traps were used then the antenna could become multi band...Sounds like a fun project for the winter.

80 metre end fed antenna summary

Overall I am very happy with this antenna. The antenna works well on 80 metres and fits into my back garden, this would not have been possible with a dipole design.

I would recommend this antenna to anybody struggling to fit an 80 metre dipole in their yard. A fun project with many more tinkering possibilities for the future.