Homebrew Choke Balun

The nest of dipoles at GM0ADX the Kilmarnock and Loudoun's club station always caused problems. The West of Scotland is a windy part of the world and it was almost impossible to keep the elements separated and the performance was described by Club's Contesters as being poor.

The nest of dipoles had a commercial choke balun which was borrowed, just to try, and was still being used two years later and we thought we should give it back to its owner (thanks Alan). Being tight fisted Scots the concept of buying something that we could built for next to nothing never crossed our minds.

The balun described here is a sleeve balun, the ferrite cores are salvaged from the video leads from computer monitor leads courtesy of those friendly folk down at the local Council recycling centre and were available just for the asking and is used to feed a W3DZZ trap dipole as described elsewhere in the website.

The other bits needed are :-

300mm length of 20mm PVC conduit,

12 ferrite cores salvaged from computer monitor video leads,

400mm UR213 cable,

20mm PVC terminal box,

PVC tape,

PL259 plug,

Fibreglass resin,

Eyelet and brass termination bolts.

  

GM0ADX nest of dipoles, for a change actually unravelled.

 

      

Solder PL259 plug on one end and Strip insulation from coax as the hole in the ferrite is too fractionally too small then cover with single layer of PVC insulating tape for good fit.

 

Feed the 12 ferrite sleeves over the coax.

 

Trim tails to length and apply several layers of PVC tape over ferrite so it is a tight when the PVC conduit is  fitted.
         
   
Fit hardware to attach aerial. note electrical connections are separate to give good connection. Tape up all joints to prevent leakage of resin.  

 

Fill with resin and remove tape when hardened.

  

Completed balun note solder connecting shorting of supporting loop. Completed balun has been tested to 400W as part a 48 hour contest with no problems reported

 

 

 

 

                                        

 

 

 

 

 

 

 

The replacement trap dipole is reported being a vast improvement of the nest of dipoles and thanks to donations from club members cost nothing to build.

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