RE: Terry Filter Tuning

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

I don't believe there is any basis to concerns about "reflected energy"
and Terry filters.  Signal reflections occur when there are impedance
irregularities and mismatches in the transmission path of a signal, and
only if the signal path is longer than twice the rise time of the
signal, i.e. with very high frequencies.  In a Terry filter, the signal
of interest (that we wish to pass without loss or reflections) is 60 Hz.
By my calculations, the signal path would have to exceed 42,000 miles
long before signal reflections become a concern.  Beyond that, the
remedy to reflections is to ensure uniform transmission line impedance
and a matching load impedance.  A Terry filter does none of these
things.

If we're talking about a primary tank frequency of 100 KHz, the signal
path would still have to exceed 1389 feet before signal reflections
occur.  The energy in the primary tank circuit has no "reason" to travel
to and be lost in the NST.  The presence of a similarly tuned secondary
is a far more "desirable" (sorry, my technical vocabulary fails me here)
destination.  This is not to say that the tank frequency is not seen at
the NST.  It is, but while a Terry filter does provide some modest
attenuation of the tank frequency, the NST is seen as a comparatively
high impedance and does not present any significant loss to the tank
circuit energy.

As to whether "reflected oscillations" can combine to create beat
frequencies and increase the primary amplitude - to do so would violate
conservation of energy.  The voltage on the tank capacitor cannot ever
exceed the initial bang-voltage, since no additional energy has entered
the pri/sec system since the start of the bang.

Regards, Gary Lau
MA, USA


> Original poster: Russell L Thornton <Russell.L.Thornton@xxxxxxxx>
>
> Reading these posts about the Terrry Filter brought a question to
> mind.  Has anyone measured/monitored the energy reflected back from
> the tank circuit?  And assuming it is wasted done some tuning to
> reduce that reflected energy?
> Russell T.
>