To make a 40 metre trap you need a piece of plastic pipe of 2¼ inch outside diameter, ordinary waste pipe is fine, about 4 metres of RG58U coaxial cable, a hot glue gun and a dip meter.  This is what you do.

1.    Cut a off a 6cm length of the plastic pipe and draw a line along it's side from one end to the other.  Rotate the length of pipe through 180º and draw another line from one end to the other opposite the first one.

2.    Drill a 2mm hole ½cm in from the ends of the pipe on the lines you have drawn, so you drill 4 x 2mm holes altogether.

3.    Drill a 6mm hole 1cm in from one end of the pipe on the line you have drawn.  You should now have a piece of pipe which looks like this:

4.   Now drill another 6mm hole at the opposite end of the pipe in the position shown in the diagram below, ie approximately 45º clockwise from the line opposite the one in which you drilled the first 6mm hole.

5.   Now take two lengths of 2mm enamelled copper wire and clean the enamel from about ½cm of each wire at a position approximately 2.5cm from one end.  Thread these wires through the 2mm holes, bend over ½cm of one end and secure it to the plastic pipe with hot glue.  Do the same with the other end. You should now have this:

6.     Prepare one end of the length of RG58 so that there is a 2cm piece of inner and a 2cm piece of braid. Tin the ends of these with solder.  Place this prepared end of the coax through the 6mm hole which is on a drawn line and solder the centre conductor to the piece of copper wire where you have previously removed the enamel and leave the braid free inside the pipe.

7.    Wind the coax round the pipe in a clockwise direction looking at the end towards which you are winding.  Cut the coax so that there is enough to pass through the other 6mm hole and leave enough inside the pipe to complete the terminations.  This should give you just over 7½ turns on the pipe.

8.   Prepare this end of the coax as in 6. above and feed it through the 6mm hole. Now solder the braid to the copper wire and the centre conductor to the free braid of the other end inside the pipe.  In cross section you should now have this:

9.    This trap will resonate at around 7.05Mhz, and you should now check this carefully. If you are lucky enough to have an oscilloscope and RF signal generator you can check the trap's resonant frequency by simply placing the trap in series with the lead from the signal generator to the 'scope and varying the frequency until the signals disappear on the scope.  Otherwise use your dip meter.  If, like my dip meter, the scale on yours will not give the accuracy required here you can use your receiver to obtain a much more accurate frequency readout like this.  Remove the antenna lead from your receiver or transceiver and replace it with a short length of wire or coax just lying on the table in front of the radio and tune the radio to 7.050Mhz.  Place the trap and your dip meter close to this wire then do your dipping. You will hear the dip meter on your receiver and you are therefore aiming to get the dip as close to 7.050Mhz as possible. You can 'pull' the resonant frequency quite a bit by adjusting the gap between the coax coils, so play around for a while until you are happy that you have the trap adjusted for approximately the middle of the 40 metre band.

10.    Without moving the coax coils seal everything in place with hot glue.  Cover the ends of the pipe with end caps for the pipe you are using.  The same hardware store that you got the pipe from will sell the end caps and you will have to cut slots in them to accommodate the attachment wires.  Seal these in place with plastic cement or hot glue.

11.    Do this again to have a pair of perfectly tuned 40 metre traps for your trapped dipole antenna.

12.    Now attach the traps to the antenna like this so that there is no strain on the traps themselves.