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QUANTUM QX PRO LOOP

    The Quantum QX Pro Loop is the result of numerous requests from DXers for a ferrite rod loop antenna that covers both the MW and LW bands.  It also incorporates a number of features that I and other DXers often find useful in their quest for that rare DX.

DESIGN PHILOSOPHY
   Many of the same principles used in the Quantum QX Loop (see the QX product page) guided the design and building of the Quantum QX Pro.  That is, quality construction, good nulling, a quiet amplifier, and attractive appearance accompanied excellent performance as guidelines in the genesis of the QX Pro.
    In addition, in order to optimize performance on the LW band, it was necessary to double the length of the ferrite rod (from 7-1/2" to 15") and modify the Quantum amplifier for increased gain at frequencies down to 150 kHz.  Two other important differences between the Quantum QX Loop and the Quantum QX Pro Loop are the presence in the QX Pro of a continuously variable Q-spoiling control (for the optimal adjustment of Q) and an external antenna jack.  Regarding the external antenna jack, any random length antenna can be connected to the tuning circuitry of the QX Pro and all other features of the QX Pro (other than nulling, of course) remain operative (including Q-multiplication).  It is with this use of the QX Pro as a MW/LW preselector that the reach of your receiver can be increased beyond that of the ferrite rod.  This is particularly important for daytime MW  and LW DX.
        As is the case with all Radio Plus+ products, each Quantum QX Pro Loop has an unlimited one year warranty...should a loop fail within a year of purchase (unless it has obviously been abused), it will be repaired free of charge.  Failures beyond the one year date are repaired at the cost of materials (labor is free).

MAIN FEATURES

     --  TUNES 150-2000 KHZ
     --  DOUBLE-BALANCED 40+ dB JFET/MOSFET AMP
     --  15" FERRITE ROD 
     --  SWITCHABLE LW/MW COILS
     --  GAIN CONTROL
     --  TILTING LOOPHEAD FOR OPTIMAL NULLS
     --  Q-MULTIPLICATION FOR SUPER SHARP TUNING
     --  CONTINUOUS Q CONTROL FOR PHASER USE
     --  EXTERNAL ANTENNA JACK
    --  LOOPHEAD ROTATES 360 DEGREES
     --  LOOPHEAD DETACHES FOR TRAVEL
     --  VARIABLE CAPACITOR TUNING
     --  ERGONOMIC SLOPED FRONT PANEL
     --  QUALITY CONSTRUCTION
   
 OPERATING CONTROLS  

    POWER ON/OFF --  Self explanatory; LED indicator.

    GAIN CONTROL -- Allows optimal setting of gain to prevent receiver overloading.

    Q-MULTIPLICATION -- Controls the degree of positive feedback for increased signal
           level and sharper passband.

   TUNING CONTROL -- Peaks desired signal.

   TUNING RANGE EXTENDER --
        MW:   H(igh)  tunes 700-2000 kHz;        L(ow)  tunes 530-700 kHz.
            LW:       H(igh)  tunes 200-600+ kHz;        L(ow)  tunes 150-200 kHz.

   Q-SPOIL CONTROL -- Continuously variable Q (tuning sharpness); used with
         Quantum Phaser for deep strong signal nulls; also used to control audio fidelity.

    BAND SELECTOR -- Switch selects LW or MW band.

    EXTERNAL ANTENNA --  Binding post for connecting external antenna.

      
SPECIFICATIONS
                                        
SIZE:    Overall height:   12"               Base:   8" x  6" x  2"
               Loophead housing:       15-1/2" x  2-3/4"  x   1-3/4"
COLOR:    Black and chrome
WEIGHT:    < 4 lbs.                                                                                                    
AMPLIFIER:   Two-stage, double-balanced JFET/MOSFET
GAIN:    40+ dB
POWER REQUIREMENTS:  9-15 VDC  (2.5mm miniplug; tip positive) 
POWER CONSUMPTION:    < 8mA
OUTPUT IMPEDANCE:  ~50 Ohms; UHF (SO-239)
COILS:  Balanced, center-tapped, Litzt/wire solenoid winding
FERRITE ROD:  Custom 15"  x  3/8"
TUNING RANGE:  150 - 2000 kHz
NULL DEPTH:  >60 dB (depends on site/signal conditions)

FREQUENTLY ASKED QUESTIONS

"Can I use the Quantum QX Pro Loop with a portable radio?"

    Yes, but see the answer to the same question under FAQs for the Quantum QX Loop.
    

"Will I be able to null my strong, local pest stations?"
    
    See a complete answer under the FAQs for the QX Loop.    

    Note two items:  (1)  Due to such variables as flux leakage along the length of a ferrite rod, shorter ferrite rods usually provide less "fussy" nulls than longer ferrite rods.  In addition, since the longer ferrite rod will generally produce stronger signal levels than shorter rods and is better at "sucking in" stray RF, it can sometimes take a little more care in rotating and tilting to obtain a maximal null. (2)  Mounting two coils on the same rod (as is the case with the QX Pro), introduces the potential problem of coil interaction and possible blunting/skewing of the nulls.  Care has been taken with the QX Pro to minimize these two potential problems but it can be noted that, in some instances, it is easier and faster to obtain a maximal null with the QX Loop than with the QX Pro.  Nonetheless, null depth is generally equal in the two loops (and independent tests indicate equal or deeper nulls when the QX Pro is compared to state-of-the-art air core loops).

 "What kind of DX can I expect to hear with the Quantum QX Loop?"

    See the FAQs for the QX Loop for MW comments.    

    On LW, so much depends on propagation conditions and your local noise levels...one night the band seems completely dead, the next it's alive with aerobeacons and transoceanic broadcasters.
    Two features of the QX Pro that I've found to be very helpful in digging out LW DX are the Q-multiplication feature and the external antenna provision.  With Q-multiplication I've been able on several occasions to narrow the bandwidth to an extreme degree and sufficiently improve the signal-to-noise ratio to eek out a CW ID of an aerobeacon.  Similarly, I've been able to extend my DX reach by connecting a 300' random length wire to the QX Pro and bring up stations that the loop alone can't detect.  With the loop alone and under good conditions, I've been able to ID very low power beacons across Canada from here in Florida and log numerous foreign beacons.  The keys seem to be "time at the dials," propagation conditions, and skill at manipulating receiver and antenna controls.

"Which loop should I buy?  The Quantum QX or the Quantum QX Pro ?"

    Well, if you DX the LW band, the answer is easy...the QX Pro.  If you are strictly a MW DXer, it's a little tougher decision.  The ferrite rod in the QX Pro is twice as long as the rod in the QX.  This, in theory (and in practice), should result in about a 6 dB advantage in signal gathering capability for the QX Pro.  Realize that this equates to about 1 S-unit of advantage.  The QX Pro does provide somewhat greater sensitivity than the QX model but the QX model, due to its shorter ferrite rod, allows less fussy nulling.  Both are "phaser ready" in that they have Q-spoiling capabilities (the QX Pro has a continuously variable control; the QX, a three-position switch).  Both also have Q-multiplication capabilities but the QX Pro has an external antenna connection for the tuning of an auxiliary antenna.  Of course, the QX is smaller and costs less.  If you are mostly a domestic MW station DXer, you might consider the QX model combined with the Quantum Phaser for the enhanced null pattern capabilities.  If you live on a quiet coastline and specialize in transoceanic MW signals, you might appreciate the greater split frequency reach of the QX Pro; combined with the Quantum Phaser, the domestic stations in the land-ward direction can be nulled for a cleaner shot at the foreign DX.