een these two currents.

To receive the 275 meters signals you will need to make several
adjustments at the same time. In the first place I would set the tuning
of the antenna circuit and of the crystal circuit about where you think
right because of your knowledge of the settings for other wave lengths.
Then I would get the local oscillator going. You can tell whether or not
it is going if you suddenly increase or decrease the coupling between
the tickler coil and the input circuit of the audion. If this motion is
accompanied by a click in the receivers the tube is oscillating.

[Illustration: Fig 118]

Now you must change the frequency at which it is oscillating by slowly
changing the capacity in the tuned input circuit of the tube. Unless the
antenna circuit is properly tuned to the 275 meter signal you will get
no results. If it is, you will hear an intermittent musical note for
some tune of your local oscillator. This note will have the duration of
dots and dashes.

You will have to keep changing the tuning of your detector circuit and
of the antenna. For each new setting very slowly swing the condenser
plates in the oscillator circuit and see if you get a signal. It will
probably be easier to use the "stand-by position," which I have
described, with switch _S_ open in the secondary circuit of Fig.
118. In that case you have only to tune your antenna to 275 meters and
then you will pick up a note when your local oscillator is in tune.
After you have done so you can tune the secondary circuit which supplies
the crystal.

If you adopt this method you will want a close coupling between the
antenna and the crystal circuit. You will always want a very weak
coupling between the oscillator circuit and the detector circuit. You
will also probably want a weaker coupling between tickler and tube input
than you are at first inclined to believe will be enough. Patience and
some skill in manipulation is always required for this sort of
experiment.

When you have completed this experiment in heterodyne receiving, using a
local oscillator, you are ready to try the regenerative circuit. This
has been illustrated in Fig. 92 of Letter 18 and needs no further
description. You will have the advantage when you come to this of
knowing very closely the proper settings of the antenna circuit and the
secondary tuned circuit. You will need then only to adjust the coupling
of the tickler and make finer adjustments in your tuning.

Af