Trap Building Instructions

All trap kits are delivered with the correct capacitance and enough magnet wire with suitable diameter (higher number of turns require slightly thinner wire do accommodate for the limited space).

Please use the number of turns in the following table to wind the toroid.


#Turns calc.: the calculated number of turns according to toroid.info. Please not that due to manufacturing tolerances of toroids, this number may vary by as much as 20%.

#Turns exp.: this is the number of turns I found suitable for my own traps for the indicated frequencies. You might likely end up with this number of turns, it is still recommended to start with roughly the calculated number of turns and remove a turn if you cannot tune the trap to the desired frequency.

Capacitance: the supplied capacitors are ceramic types with either 500V oder 630V rating. For the lower frequency traps you may get two 300pF capacitors instead of a single 600pF capacitor. In this case, please solder one capacitor on each side of the trap board.

Band    

6m    

10m    

15m    

17m    

20m    

30m    

40m    

60m    

80m    

Frequency    

50.290

21.120

21.080

18.097

14.070

10.142

7.040

5.354

3.580

Capacitance   

68    

68pF    

100pF

120pF

150pF

200pF

300pF

600pF

600pF

#Turns calc

6.1        

10.8    

11.8    

12.6    

14.6    

17.5    

18.6

17.3 

25.9        

#Turns exp.

5        

9    

10    

11    

13    

16    

17

16    

24        

Toroid Type

T50-6

T50-6

T50-6

T50-6

T50-6

T50-6

T50-2

T50-2

T50-2        

Toroid Color

Yellow

Yellow

Yellow

Yellow

Yellow

Yellow

Red

Red

Red        

Assembly:

1. Wind your toroid with the number of turns indicated in above table with the supplied magnet wire. Generally start with one turn more and reduce as indicated.

2. Solder the capacitor on either size of the trap board (you might get two capacitors for higher bands, in which case please solder one capacitor on each side).

3. Remove the enamel on the magnet cable ends: find the location where you the cable will meet the trap board pads and remove the enamel by either heating up that part of the cable with your soldering iron and enough soldering tin (please do not inhale any fumes) or use sanding paper or a sharp knife to remove the enamel.

4. Slip the board through the toroid and solder the magnet wire to the trap board through the thinner pads (not the ones marked with a circle on the silk screen, those are for soldering the antenna wire). Please note that trap board orientation depends on how you wind the toroid. If the winding does not match the solder pads, please flip the board.

Tuning:

In order to tune the trap to the desired frequency you need to adjust its resonant frequency. You can vary the frequency my squeezing the windings on the toroid - close winding will increase frequency while larger spacing will lower the trap’s resonant frequency. If you cannot reach the desired frequency this way, remove one turn (see above about having an extra winding to start) and try again.

Tuning can be done with a VNA or antenna analyzer by having one or more winding of wire going through the core of the finished toroid attached to the VNA/antenna analyzer and looking for a dip in SWR. The dip marks the trap’s resonance frequency.

Please watch this video for a more detailed explanation.