- Trap Test & Tuning - Time to test your coils. This description is mainly obtained from the help-file in the CoaxTrap software. - Test Setup - The exact operating frequency of the traps may be determined with a grid dip meter. If desired, a signal generator and detector may be used as illustrated below: I use a RF-Signal generator to inject RF-Signal at one end of the coil,- i monitored the RF-Signal at the other end of the coil using an oscilloscope. The test circuit. Closeup The signal generator may be a normal bench signal generator or other RF generating device such as one of the MFJ antenna analyzers - or even a transmitter set to the 1 watt or less output level!. Tune the signal generator through the trap frequency. The oscilloscope or volt meter will indicate a minimum at the trap frequency. If an oscilloscope is used, it is quite possible that the second harmonic of the signal generator will become the visually dominant signal since the attenuation at the trap frequency is “very high” and the signal reaching the oscilloscope at the trap frequency becomes “very small” compared to the strength of the second harmonic which is passed through almost unattenuated. As a result, the RF probe and volt meter might be more desirable. The trap frequency may be lowered by increasing the number of coil turns or increasing the length of the shielded coax protruding into the coil form. The trap frequency may be raised by reducing the number of coil turns or by decreasing the length of the shielded coax protruding into the coil form. Small changes in frequency (10’s of kHz) may be made by bending the connections in the coil centre closer to the inside surface of the coil form to cause a small change in the effective capacitance and inductance. This effect is most pronounced when the length/diameter ratio is 1.0 or greater. Test Results Here is some images illustrating coil attenuation at resonant frequensy 6680 kHz. Signal @ 6680 kHz Signal @ + 6 kHz Signal @ + 12 kHz <-- Go Back! ©1999-2006 SM2YER Goran