Simple 6 Meters End Fed Unun

1, Introduction

Few days ago I got a phone call from a very kind old man in North-Pole, he asked me about what did I want for the X'mas.  I sooner replied him it had been a very long time for me not to do QSO on 6 meters and I wanted to keep on-air again with a proper antenna.

Next day morning when I woke up, it just happened to me to find a roll of dia. 0.8mm enameled wired under my bed so I decided to build an unun with the use of it.  "Thanks Santa, ho ho ho......."  

2, Methodology

I've heard lots of misunderstanding and misleading about building the air-core coil from local HAM chats.  Although my method might be not the best but it could be the simplest and easiest way to design a proper one by using the CAD/CAE.  The program I used is called "Vertune", you can get it from the internet free.  Just input your requirements and let the computer to do the rest for you, sit back and enjoy......!!!



3, Bill Of Materials

- dia. 25mm white conduit
- dia 0.8mm enameled wire
- banana socket
- BNC socket



4, Construction

The air-core coil is nothing simpler than about 13 turns of dia. 0.8mm enameled wire wound on a dia. 25mm white conduit with 2 turns tap for 50 ohm input.  The length of radiator is about 2.85 meters.  Trim it for best VSWR with an antenna analyzer.



5, On-Air

I always use my FT-897D on 6 meters due to its all mode feature.  Last night I tested it with friends from Hong Kong East and Shatin, they reported that a noticeable improvement of my signal strength and audio quality has been observed.  I also tried 50w for Tx, there was no temperature difference on the coil.  Then, I switched to my VX-6R and used only 0.03w (30mw) to see if I could still make contact. 

Wow........!!!  With such QRP power this antenna still kept me alive on the band to do QSO with HAMs from Kowloon East and Hong Kong East.  Amazing....!!! 

6, Conclusion

The program demonstrates about an overall 98.8 % of radiating efficiency based on above design parameters.  Knowing that this is only the modeling result and assuming 20% of the efficiency will be reduced due to poor workmanship, it's still a good antenna.

Merry X'Mas 2008

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73's de VR2UIX