Vectronics SWR-66 - Manual (Page 2)

SWR-66 Dip Meter Adapter Owner's Manual
2
This has the advantage that stray coupling is reduced and frequency pulling of the oscillator is
eliminated. Frequency readings can thus be made with more precision.
To insure accurate readings always keep the coupling as loose as possible while still getting a
readable dip.
Maximum coupling is obtained when the coupling coil is either placed inside a larger coil under
test, placed against a coil of equal size or placed over a coil of small size. When using the
smaller coil to couple with a very small coil, such as a molded inductor, the outer plastic sleeve
must be removed or cut to allow the molded inductor to be inserted into the small coupling coil.
Otherwise coupling may be insufficient to create a dip.
Once a dip is found the coupling coil and the inductor of the circuit under test should be
separated until the dip is barely evident. The frequency should be read at this point for maximum
accuracy.
The coupling coil can be removed and the coupling coil jack can be used to directly feed a one or
two turn link coil on a toroidal inductor. The coupling can be easily varied when testing resonant
circuits containing toroids by adding or removing turns from the coupling link. Never try to
couple with the standard method of using a double link. The air wound external link acts like a
shorted turn on the toroid and lowers the inductance. This "shorted turn affect" will cause
inaccurate measurements for many types of toroids.