Easy 60m addition to an 80m OCF

 

My 80/40m Ocf dipole is an efficient aerial albeit low and bent to fit in to my garden.

My daily 80m sked at 13:30 has had to move to 60m as the solar cycle progresses and the Nvis signals were impossible on the 80m band. (GM to GM and GM to G all within about 100km)

Unfortunately for me on 60m the 80/40m OCF was found to be woefully inadequate with the tuning unit eating up most of my poorly propagated RF.

I have a high local noise on the low bands so getting low noise from the OCF on 60m was a sure sign of a poor performance, confirmed by poor signal reports

My OCF aerial is U shaped as I squeeze it in to the available space and farther away from the local noise source. Of course the aerial is better suited to being flat top and in a straight line so like most amateurs I need a bigger garden !

To be clear about my existing feed arrangement, I have about 40m of Westflex 103 feeding my auto atu, from there we have another 15m of RG8X to a telescopic mast in the bottom corner of the garden. So this is a coax fed 80m OCF dipole with a 4:1 balun at the feed point and a total of 55metres ( 180 feet in old money) of coax.

To get the aerial to perform more efficiently on 60m the addition of a single wire connected in parallel to the long side of the OCF will effect a solution .

On the opposite side of the feed point no additional wire is required as the existing OCF short side wire operates as the other side of the 60m dipole .( not quite the correct dimensions but close enough )

By simply adding around 13.5m (45 feet) and hanging approx 10cms (4 inch) or so below , I use open wire feeder spacers and then connecting this wire together with the long side of the OCF to the feed point at the balun

I modelled the additional wire initially on Mmana-Gal ,this allowed me to alter height above ground , wire length , spacing etc

Your aerial setup will be different but by a bit of experimentation I`m sure you will be able to get much better 60m performance from your existing 80m OCF by the simple addition of the extra wire

My SWR readings are

 3.650 …. 1:1

5.301...... 1.5 :1

7.15....... 1.8:1

Drop me an email if you wish the Mmana-Gal ?.mma file where you can play about wire dimensions .

This was published in SPRAT 199