Hammarlund Manufacturing Hq-170a Communications Receiver Manual

							file:///C|/BoatAnchors/Hammarlund/HQ170A/HQ170SVC.TXT
should be installed using as short lead length as possible, and preferably mounted inside of the 
receiver bypassing each of the relay terminals to ground.
We have recently received a few complaints advising that the slot depth control on the HQ-170 
receiver is apparently inoperative.  This we can assure you is decidedly not the case, since from 
all indications, too much is being expected insofar as the effect of this control being very 
noticeable is concerned.
The slot depth control is actually a very gradual vernier adjustment.  In view of this its effect 
will not be very noticeable unless the proper procedure is employed.  The suggested procedure is 
as follows:
Tune in an AM signal on any band or any other strong constant carrier of similar nature, such as 
crystal calibrator.  Whenever the receiver is being tuned for normal reception  be sure to first 
rotate the slot frequency control to the extreme clockwise or counter clockwise position.  In 
other words, never leave the slot frequency control at or near the zero setting.  If this 
procedure is not followed it is obvious that the center of the pass band will be slotted out, in 
some cases this being quite obvious by producing 2 spot tuning or 2 peak S meter readings.
After tuning in the constant carrier and peaking the S meter, taking the above precautions, rotate 
the slot frequency control.  It will be noticed that upon approaching the zero setting, the S 
meter reading will be effected.  A very definite null or minimum S meter reading will be obtained 
with the slot frequency control adjusted at or near zero.  Observe this S meter reading.  With the 
slot frequency control set at the minimum S meter reading position, the slot depth control should 
be rotated very slowly throughout its range, observing the S meter.  It will be found that one 
particular spot throughout the range of the slot depth control a further reduction in the S meter 
reading will be obtained.  Once this setting has been obtained, the slot depth control may be left 
permanently in this position, and all future slot filter adjustment made by the slot frequency 
control only.  A check of the slot depth control setting may be advisable periodically.
It is hoped that the above information will prove of interest and assistance.  If after following 
the various suggestions, trouble cannot be eliminated, please write to us supplying as much 
detailed information as possible in order that we may endeavor to be of further assistance or 
authorize return of the receiver for repair.  Please refer to terms of our warranty on the inside 
rear cover of your instruction manual which will apply under these circumstances.
Erratic performance in the triple conversion bands, such as a temporary loss of gain after a 
period of transmission or stand-by operation, which is cured by rotating the band change switch or 
turning the receiver off and then on again, usually involved the second 6BE6 converter of V3 in 
the schematic diagram.  If changing this tube does not permanently cure this condition, changing 
the value of R10 from 22K to 47K is recommended.
If a new 6BZ6 in the crystal calibrator does not result in improving the output of the crystal 
calibrator to your liking, additional output may be obtained by increasing the screen voltage, 
this is accomplished by merely adding an external « watt resistor from 47K to 100K across 
terminals or leads 3 and 4, of the couplate Z1 in the schematic diagram.
If upon checking the 100 kc calibrator against WWV using another receiver it is not possible to 
zero beat the calibrator by means of the adjustable trimmer, and the crystal appears to be low in 
frequency, the frequency of the crystal can be raised by substituting an external 470K « watt 
resistor, for the one in the couplate Z1.  This is accomplished by unsoldering lead /7 of the 
couplate from one side of the trimmer and connecting the external 470K resistor across the trimmer 
terminals.  This change will usually make it possible to zero beat a crystal that is too low and 
out of the range of adjustment provided by the trimmer.
Please remember that the low frequency response of the receiver is increased when the audio gain 
control is employed at the lower end of its range.  This is the result of the auto response 
circuit.  Increasing the audio gain control setting to a position past straight up and reducing 
the RF gain will make it possible to obtain the same volume level with less low frequency response 
and usually better signal-to-noise ratio.  If it is desirable to reduce some of the low frequency 
response at the lower settings of the audio volume control, the auto response feature may be 
dispensed with by merely short circuiting resistor R47, 47 ohms.  This results in removing the 
feedback which provided the better low frequency response.
Very truly yours,
THE HAMMARLUND MFG. CO., INC.
Frank I. Lester, W2AMJ
Sales Manager
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