New-York tribune., 1922-08-20
Reflex System
] Latest Method
Of An,l'lifyinnsgs 9
Unique Circuit Invented by
Boston Engineer Gives.
Six Steps Amplificasion
ON Three Vacuum Tubes
Uses Crystal as Detector
Vacuum Tubes Used Anplify
Audible as Well as Radio
Frequencies asSane Time

The most unusual adaptation of the
cascade method Of using vacuum
tubes by combining radio and audio
frequency amplification has been in
vented by William Preiss, radio en-
gineer Of Boston The new system is
known as the reflex receiver, and it's
novel feature lies in the fact that
with it six stages OF amplifcation are
obtained by means of three tubes.
The three tubes are first used as
radio frequency amplifers for the
purpose of building up the incoming
signal When this has been done
rectifcation is obtained by means of a
crystal detector, after which the recti-
fed current of audible frequency is
again passed through the three tubes
and amplified, for loud speaking.
The system is undoubtedly the most
notable advance in the step by step
method of amplification, and is de-
signed for economy OF operation and
construction. The entire receiver can
undoubtedly be contained in a very
compact case, and will operate sue
cessfully on loop aerial.
Based on Tube characteristics
1t is based on the we'll known ampli-
flying characteristics of the vacuum
tube COUPLED with the better rectifying
qualities OF the crystal detector. Radio
frequency amplification is obtained by
means of suitable high frequency
transformers designed for short wave
work, coupled to the tubes in the nor
NAL manner.
Just how we'll these will work on the
short waves used in radio-phone broad
casting, where frequencies of $4,000
cycles per second are involved, / cam
not say at present, but providing the
vacuum tubes arc we'll matched with
the transformers there should be no
difficulty in this system, especially as
rsctiiication is performed with crystal
with the consequent result that there
is no feed back from the plate circuit
CT a detector tube.
1t is not generally understood by the
new armyof radio fans that the crystal
as a datector is far more efficient and
sensitive than is the vacuum tube in
q straight circuit. This is due to the
fact that the vacuum tube is not per-
feet valve. This can be readily under
stood when it is taken into considera
tion that the tube works well as an am
plifiei OF high frequency currents. The
value of the tube as q detector is built
up by the regenerative circuit.
Crystal Needs Adjustment
The drawback to the crystal detector
however is the fact that it needs con-
stant adjustment when weak signals
ere concerned, and especially signals
that consist of a varying degree Of
amplitude. such as 9ilc voice currents
in the radiophonc.
The new system takes advantage of
the good points of the vacuum tube
and the crystal, and combines them.
The three stages Of radio frequency
build up the incoming signal thousands
OF times, until the resultant current is
strong enough to be passed through
the crystal detector-with the latter at
almost any setting. In fact, it can be
screwed down fai-ly tight. and vet
function well without Interruption.
Even fairly heavy vibration will not
hurt it.
The trick in the new system ther
consists of passing the uni-directonal
pHsations that are passed ont by the
clSStal dGlecfoT into the three tubes
again for further amplifcation These
are the currents that correspond in
frequency to the sounds (either voice
Or music) sent out by the broadcasting
station, and are of audible freuuencies.
Standard Circuits Used
& The circuits about the three tubes
for this purpose. of course, are of the
regulation standard frequency
amplification type, using standard
audio-frequency transformers. set
already has been constructed on this
principle, and | am informed that it
operates vol,- cco~sfully, oayticularlv
on loop aerial. ] have not seen it in
operation, however, but expect to do
SO shortly.
One of the advantaees Of the crystal
detector for radio-phone reception is
he fact that it is free from many of
the noises that are inherent in vacuum
tubes, and which are amplified bv the
audlo-freeuency amplifiers In this re
spect, Theoretically at least, The new
system should be very rood. There is.
however, the old difficulty of amplify-
ing the very high frecuencies that are
involved in short-wave work.
There is every possibility that the
rev system will be tried out alongside
the original Armstrong suner-regener-
ator within few days. in order to
ascertain the comnarative worth of the
two systems. Both use three tubes.
Py9Nyizer GSoror