INSTRUCTIONS
for
Q X' er
R.L . DRAKE COMPANY
I.GENERAL DESCRIPTION OF Q-X’ER
The Q-X’er is an attachment for a radio receiver. Its main purpose is to help discriminate between the wanted signal and interfering signals. The purpose is the same as for a crystal filter but the Q-X’er in operation is a much more effective device. Three modes of operation are provided for as follows :
1.NOTCH - With the selector switch set in the NOTCH position, a very sharp rejection notch may be tuned across the pass band of the receiver to eliminate an, interfering carrier or heterodyne. The general shape of the receiver pass band is unchanged and the notch is so sharp that it is almost imperceptible in the audio of the desired signal. See Fig. (1).
2.BOOST - With the selector switch set in the BOOST position again the general shape of the receiver pass band is unchanged (though lower in amplitude) but a sharp spike is imposed on top of the response. This spike may be tuned across the pass band to boost any single frequency. See Fig. (2). Generally, this position of the switch is used to boost the carrier of a weak phone or broadcast station to prevent distortion due to selective fading, etc.
3.PEAK - With the selector switch in the PEAK position the pass band of the receiver is narrowed to a very selective response only a few hundred cycles wide. Fig. (3). This is ideal for C. W. reception.
The Q-X’er TUNING control can be used for a fine adjustment in tuning in the signal. (Tuning here does not change the Beat Frequency note).
In principle of operation, the Q-X’er is simple. It is a two terminal device shunted across an I. F. transformer ‘in the receiver to act as a gate letting through the desired frequencies and stopping the undesired frequencies. The Q-X'er achieves its performance through the use of an efficient, stable Q multiplier circuit. The Q-X’er acts just like a resonant circuit with a Q of approximately 3000. This accounts for its sharp peak or notch.
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5.Ground the shield of the I. F. coax cable to the chassis unless the receiver has a “hot” chassis as in an AC-DC set. In “hot” chassis receivers do not connect the shield; cut it off and tape the end to prevent accidental connection.
6.Remove two nuts on back of Q-X’er and pull off back cover and case.
7. Set Q-X’er switch to “OFF” position. Carefully adjust input coil, |
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L2 (see fig. 5) for maximum “S”.meter reading. |
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8.Set Q-X’er switch to PEAK. Set PEAK ADJ. control to a point just below oscillation. Rotate Q-X'er TUNING knob to peak carrier (maximum “S” meter reading). This should occur at the center of the Q-X’er tuning range. If it does not, adjust the screw on the shielded coil, Ll (see fig. 6), to peak the carrier at this point.
Note : These two coils in the Q-X'er are factory adjusted to
455 KC. Your adjustment takes care of any small deviation from 455 KC in the receiver I. F.
9.Replace cover and case. Q-X’er is now ready for use.
Changing length of I. F. coax cable will cause detuning of L2. If the length must be changed, L2 must be retuned as in Step 7 of “Installation Instructions”. We recommend that the unit be adjusted and operated as shipped before a change in cable length is attempted.
III. OPERATING INSTRUCTIONS
Finding the Notch - When you first use your Q-X’er, you will probably have trouble locating the notch. The NOTCH ADJ. control is a balancing adjustment for which there is only one correct setting. This setting will give maxi-
mum rejection for all conditions. For good notching, the NOTCH ADJ. control must be set to within about l/16” of this point.
To set NOTCH ADJ. control for the first time follow these instructions:
1.Locate the approximate setting of the TUNING dial for some stable heterodyne by using the BOOST or PEAK position.
2.Turn switch to NOTCH and carefully turn the NOTCH ADJ. control until some rejection of the heterodyne is observed.
3.Slight adjustment alternately of TUNING and NOTCH ADJ. will give maximum rejection of the heterodyne.
4.Leave the NOTCH ADJ. control set at this position. It will give best notching over the entire tuning range of the Q-X’er and probably never need to be changed very much.
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