National AN/WRR2-B
More Pictures

The bottom drawer is the RF converter; the top one is the IF portion.


These, are few pictures of the RF drawer.




Click here for Block Diagram

Alignment cookbook

Concentrate on the synthesizer portion first.

1)  Make sure that the 1 MHz oscillator works

        2) Make sure that the 1 MHz-500 kHz divider works

        3) Make sure that the 500 kHz-200 kHz divider works

        4) Make sure that the 20 kHz divider works

5) Align the harmonic generator.  It is VERY important that the end points are right. The  procedure provided in the NAVSHIP is cumbersome and made up for 1950s test equipment. Don't try to "short circuit" that procedure by picking up the signal directly from the plate of the oscillator;  any direct connection will load the oscillator and screw up your readings.

Alternate procedure:
Here is an an alternate procedure that will make the alignment of the harmonic oscillator easy.  For this, a high impedance counter is required or a scope with a 50 ohm CH1 output such as a Tek465 and a 50 ohm counter.  In this case, the scope is used as a high impedance amplifier for the counter.  (If a high impedance counter is not available, use a well calibrated receiver }

        6) Align the  interpolation oscillator.

        7) Align the 5 kHz and the 500 Hz dividers.

8) At this point as you tune the receiver, the 100 kHz meter should dip every 100 kHz. The same thing should happen with the 500 Hz meter but every 500 Hz.  If you cannot get to this point, don't go any further. Go back to the applicable step.
        9) Now, complete the alignment of the receiver following the NAVSHIP manual.
Note: For steps 1 to 8, there is NO need of making all connections between the RF and the IF unit.  Power to the RF unit is all that is required.
Note: I modified the bottom cover plate of the harmonic oscillator to facilitate its alignment.  The mod consists of adding a SMA connector, a pickup coil and a simple LPF.
 Harmonic oscillator mod
Last update 22-1-2002