Well my old dipole finally broke, an 80/40 that worked well. I decided to go from scratch and build new 40 meter traps while I was at it. A ham friend of mine wanted me to build him some also, so I thought I'll just post pictures so that someone else who has never built traps could learn how. They are very easy to build.
Start out with a couple pieces of PVC 5 1/4 inches long. Mine are 1 1/4 inches in diameter and I used RG-8 for the turns. It can vary in length and diameter, and the number of turns you use will depend on this. There are many coax trap calculators online just put in your core diameter and length and it will tell you the number of turns for your target frequency.
Drill holes approximately 4 inches from the end, one on one side one on the opposite side. If you calculated you need X number and a half turn or quarter turn then drill in that place. While your at it drill 1/8 TH inch holes 3/8 in from each end. (this is what you will solder your dipole wire to)
Thread one end of your coax through the hole you drilled and leave about 8 inches hanging out the center.
Wrap the calculated amout of turns you need. On mine I calculated I need 14 FULL turns, if you need another half or a quarter turn you would drill the hole on the opposite end naturally in a different place.
Strip off the outer coax plastic coating being care full not to cut the shielding.
Now close to where you started the cut use a probe and work the coax to one side. Next pull the center conductor through at this point.
At this time mark your trap "T" on one end and "B" on the other. Both traps have to be facing the same direction once you put them in the air and it will make the next part a little less confusing.
Alright take your braid from the T end and pass it through the center to the B end. This will be soldered to the center conductor on the B end.
Now cut off excess from this connection. I use coax seal on it to keep water out. Then tuck it back inside towards the center of the trap.
Almost done. Yours should look like this, one center conductor out the "T" end and one braid (shield) from the other end "B" sticking out.
Now thread a heavy gauge wire (copper*) through the 1/8 TH inch holes you drilled close to the end. This is the "T" end so your center coax conductor will be soldered to this copper wire. Your dipole wire will also solder to this loop. The other "B" end will have a loop and the braid soldered to it and will have other end of your dipole wire soldered to that loop .
There you have it. Make sure you solder you dipole wires well, and make a good mechanical connection. This means to twist your dipole wire to the loop then solder. Also make sure you have both "T" ends pointing in the SAME DIRECTION. I put both "T" 's pointing Toward the center feed of my dipole.
I used a heath kit Grid Dip Meter to check my traps. You want them just under 40 meters, mine came out to 6.9 MHZ so I am pleased with them.
* There is always one of these right? If you use anything but copper for these hanging / soldering loops it will throw your trap WAY off. Been there done that bought the T shirt. :)
