KeepITCHeap!  
   

A beginners 23cm yagi
COMPONENTS LIST:
1 metre (or more) of Westflex103
A mug of coffee (Optional )
That's all !
This is not intended to replace a proper or commercially manufactured aluminium yagi, but will get you local atv pictures quickly & very cheaply and has an swr down to below 1.3:1 on 1255 Mhz


 
   
 
   
   
PICTURE 1
 
PICTURE 2
        
   

Cut a length of cable to 130mm. This will be used for the matching balun which should be 10.5cm long plus the 10mm at each end for connecting to the dipole.
Using a stanley knife cut into the remaining cable down to (but not through) the centre conductor at 500mm length. Draw off the outer, braid and sheath and plastic spacer from the cut exposing the copper centre wire.Keep for later use.
Trim back 10mm of outer black pvc fold back the braiding and bend the wire as shown in pic1 to bring the centre of the folded dipole level with the westflex cable in order to let the reflector and director wires align with the middle of the dipole when viewed from the front.

     
   
The reflector element (extreme right in picture 2) can just be soldered to the braid on the top of the cable, but a loop around the cable allows a twist above the cable as shown which raises the reflector to be inline with the centre of the dipole. A piece of centre conductor of at least 220mm will be needed and can then be trimmed down when fitted ok.
      
                   
   
           
   

PICTURE 3

    
PICTURE 4
        
   
     
   
 
   

Slice 10mm of the balun wire outer sleeving , copper sheath and braiding off leaving the centre wire and its plastic spacer. Trim off the end 5mm of this inner sleeve so that the end 5mm of centre wire is exposed.Solder the two ends of the balun (A and B ) to the dipole and the braiding should be soldered as near as possible to the braid of the main cable(C). You may find that a piece of braiding taken from the off-cuts will wrap around the baluns' braiding and enable a good solder joint to be made.

  
   
       
   
In the picture above right you can see the strengthening wire which also supports the front director element (left of picture). Carefully bend the support wire to give the 18mm spacing to the dipole and set the director to be in the same central plane as the reflector i.e. centre line through the dipole
  
   
 
   
The completed aerial. The balun is important as it matches the 50 ohm cable to the higher impedance of the dipole. This reduces the losses significantly.        
   
     
   
Used indoors, in a loft ,this will last for years, if used outdoors you will need to paint or varnish the whole aerial or even enclose it in a plastic cover to protect it from the weather.
It is not intended as a long term aerial , just as a cheap and quick way for the impoverished novice to get local atv pictures.Depending how far you are from the transmitter a small preamp would be advisable, ideally at the aerial end to help overcome losses and noise in the down cable.
      
   
     
   
You can run a few watts in from a 23cms PA if you have one and adjust the swr for minimum reflected signal. Otherwise you will need to tweak the spacing between the elements for best results on receive. If you decide to make one let me know how you get on and especially how well it works at your location. Any refinements or modifications are welcomed and will be shown here for the benefit of others, but mods must meet the basic criterium .... K.IT.CH !