WJ-8711A

The WJ-8711A uses the SDR technology in hybrid form, ie adopting a superheterodyne configuration with the last IF digitized to perform the filter and demodulation functions. The equipment has professional features both in terms of RF performance and reliability, the manufacturer Watkins-Johnson has in fact designed this model mainly to the military and for this reason the operational specifications include resistance to vibration, shock, humidity, atmospheric pressure, storage temperature according to the MIL-STD-810D standard. The receiver offers a lower limit of only 5 KHz, although tuning can go down to 0Hz under the operational aspect. In fact the WJ8711, starting from hundreds of KHz and up to the 30 MHz, guarantees a precision in the detection of the amplitude displayed by the S-meter equivalent to a measuring instrument in standard S-points/dBm. The automatic gain control operates in analog and digital sections for a total of 1OOdB, the response time is extremely rapid, taking 5 milliseconds while the release time is selectable between slow, medium and fast. After the ADC conversion stage operating at 100 Ksps with 16 Bit resolution a DSP processor is responsible for defining selectivity and making the PBT, notch, BFO adjustable functions available (within ±8000Hz in 10Hz steps), multi-mode demodulation including also the ISB or independent sidebands with two audio channels.

The radio has 66 different bandwidths to choose from a minimum of 56 Hz to a maximum of 16 KHz, the form factor of the filters is always better than 1.5 at 1 (6/60dB). In the following table the nominal bandwidths referred to 3 dB:

The front-end is characterized by excellent IP2 and IP3, to shift the dynamic range at the input you can insert a 10dB preamplifier or a 15dB attenuator. However, there is not a preselector stage which is supplied only as an optional accessory (model HF-8711 - PRE), this integrates no less than eleven preset bandpass cells with a width of less than one octave and can be switched off when necessary.

The receiver uses a high stability TCXO with ±0.7ppm for an excursion of 50°C in temperature. Installing the internal option WJ-8711 - REF the stability can be further improved. An input is also dedicated for an external frequency reference that accepts signal at 1, 2, 5, 10 MHz. The receiver automatically detects its presence and adopts this master signal. The audio is usable for loudspeakers, headphones and via fixed-level outputs for connection to recording systems. The volume control is separate for audio intended for the speaker and headphones. Two IF outputs at 455 KHz with different bandwidth makes possible to connect a spectrum-scope and even a specific demodulators that make use of the selectivity determined by the WJ-8711A. An RS232 serial interface with baud rates of 75/9600bps allows remote use of this WJ. The apparatus has standard size measurements so as to be possibly mounted in a standard 19 inch rack.

WJ-8711A performance and practical notes :

The 8711A is a superior class receiver for reliability and repeatability in performance. Its characteristics are similar to the WJ-1000A intended for the civil market, but there are significant variations with respect to the latter as the maximum bandwidth of selectivity. Having been designed in the first half of the '90s this Watkins-Johnson inevitably suffers from some weaknesses when compared to the most recent radio-set but expresses the ergonomics guaranteed by a front panel where each command is rationally enslaved to specific buttons and rotary controls.

WJ-8711A price

We have collected for your convenience the Watkins Johnson WJ8711 sale price (US Dollar) and its trend over time. Useful to guarantee a cheaper purchase of this radio and to put it for sale in the second-hand market. Of course offers, accessories, warranty terms and conditions can lead to different figures.

Price	Date	Condition
USD 1858.00 (1595EUR)	2020-nov	Second Hand With preselector
USD 2029.00 (1790EUR)	2019-may	Second Hand With preselector
USD 1999.00	2019-apr	Second Hand With preselector