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Watkins - Johnson, Gaithersburg, Maryland

WJ - 8718

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überarbeitet am 2.11.2010

As a successor to the WJ-8888, Watkins - Johnson brought out another professional grade communications receiver in 1976 the WJ-8718 / WJ-8718A (1982).
The AN/URR-74(V)2 is a military variant of the basic receiver, the receiver has been adopted to the needs of the U.S. Navy; later the set got a microprocessor controlled front panel and the designation WJ-8718A/MFP.

Doppelsuper,

Digitalanzeige, max. 10 Hz

AM, CW, LSB/USB, ISB, FM

10 kHz - 30000 kHz

Selektivität -6 dB
0,3 / 1,0 / 3,2 / 6 / 16 kHz

Sensitivität < 0,4 uV

RF-Gain, AGC fast/slow/man

 

The professional shortwave communications receiver WJ-8888 is contructed as a 19 inch rack receiver in a matching cabinet. Even the rack version itself measuring 483 x 134 x 493 mm has a weight of 15,8 kg.
The receiver can be powered from 115 or 230 V mains.

At the right side of the front pabel, You find the rugged tuning knob, the tuning speed can be selected by four pushbuttons next to it, the fifth is the LOCK position.
The yellow LED frequency display located above the main tuning knob, will show You the frequency, the radio is tuned to, with an accuracy of 10 Hertz.

The receiver is equipped mainly with pushbuttons with a mechanical indicator, whether the function is active.
In the top row of front panel elements, You find in the left upper corner the signal strength meter which can be set to display the R.F. signal or the audio signal level, it is calibrated in dB. On the right side of the typeplate, there is a BCD switch coding the BFO offset frequency.
The leftmost pushbutton in the middle row is the main power switch, followed by the meter mode switches, the AGC mode switches to select manual or automatic gain control with slow and fast decay time and the "detection mode" buttons, the WJ-8718 does not only demodulate standard AM signals, but also CW, USB, LSB and ISB (independent sideband) and narrow band FM. In the independent side band mode, a different content is transmitted on both sidebands of a signal, this mode was used for feeder signals to shortwave relay stations in other continents, e.g. to feed the french content on one and the english on another sideband.
In the bottom row, You find the headphones jack, the R.F. gain and headphones level control and the I.F. bandwidth filteer selector, my WJ-8718 is equipped with excellent 0,3 / 1 / 3.3 / 6 and 16 kHz fiters, a good choice for most DXing conditions.

The operation scheme is something You have to get used to, the WJ-8718 has this in common with other professional receivers:
First You have to connect an external active speaker to the line out jack at the rear of the receiver, or You just use a pair of headphones.
After switching on, set the receiver for the reception of a standard AM signal, activate the buttons AGC FAST, 6 (kHz) and AM, so that You can receive standard AM signals. Use the main tuning knob to tune the receiver to the desired frequency, You can select different tuning speeds to arrive at the desired frequency quickly, but the receiver has no internal frequency memories. And it was not before Watkins came out with the WJ-8718A/MFP with the "Microprocessor Front Panel", when direct keypad frequency entry was available.

The performance of the WJ-8718 on the shortwave bands is excellent, the set is rock stable even in SSB modes, I like the ISB mode for AM DXing in ECSS technique and then select the sideband with less interference. In contrast to some semiprofessional amateur radio receivers, the WJ-8718 comes without features like passband tuning, a notch filter or a noise blanker, so the good old Dierking NF nocht filter might be quite useful with it.

© Martin Bösch 28.9.2010 / transl. 14.11.2010