Receiver Review: Watkins-Johnson HF 1000

HF1000

Year Introduced/Discontinued: 1993/1999
Power: Mains (97-253 VAC)
Size: 133 x 486 x 508 mm
Weight: 6 Kg
Price: US$3800, CAN$5400, £5400
Coverage: 5 kHz - 30 MHz, synchronous AM, FM, CW, USB, LSB and ISB

Value Rating star starstarstarstarstar

 

March 2000 Update

In the latter half of 1999 the Watkins-Johnson Company was sold off in pieces to several different buyers. This included the Telecommunications Group manufacturing the HF-1000A and other receivers. The HF-1000A model, based upon the WJ-8711A receiver, was discontinued in December 1999. The WJ-8711A has a suggested retail price of US $5110.

By early 2000 there were new Web pages at the new URL of http://www.sigintel.com/. Compared to the old Watkins-Johnson pages, this site has a completely new look to it, including a fill-in-the-request-form for product information. The data sheet for the WJ-8711A receiver, upon which the HF-1000 was based, is located at http://www.sigintel.com/sig/webu/internet_site.view_page?p_page_id=16 1

The home page states "Formerly Watkins-Johnson Company's Telecommunications Group, the Gaithersburg Operations is now a business unit within the Aerospace Electronics sector of BAE SYSTEMS. The facility specializes in radio frequency (RF) electronic products, offering innovative state-of-the-art equipment for applications in communications surveillance, direction finding, and signal processing." The business unit name is named "SigIntell."

The Gaithersburg postal address and telephone number is: BAE Systems, 700 Quince Orchard Road, Gaithersburg, MD 20878, USA.
Phone: (301) 948-7550.

 


This review was compiled independently. The Medium Wave Circle and Radio Netherlands has no financial connection with Watkins Johnson, the manufacturer of this receiver.


Reviewers: Tom Roach, Jonathan Marks, Willem Bos and Diana Janssen.

In the waning months of 1993 shortwave listening hobbyists witnessed the announcement of the Watkins-Johnson HF-1000 receiver. It boasted 59 I.F. bandwidths (ranging from 56 Hz to 8 kHz), computer control, and digital signal processing (DSP). It had enough knobs, LEDs and buttons to satisfy even the most insatiable hardware gadgeteer. The ads hinted that this receiver was a descendant of a receiver made specifically for unnamed (NSA anyone?) three letter agency(s). It also came with an astounding price tag of almost $4,000 US dollars! How well does it work, and is it worth the cost? Bottom line? It is not a beginner's receiver. There is a learning curve to this high-end digital receiver, but the results can be rewarding. Reasonably good antennas pay dividends. Under certain conditions, you may encounter audio distortion. Above all, listen to what you get and compare. Clearly, for those who listen only to broadcast programming there are less expensive alternative choices.

 

Operational

The receiver comes with handles and a front panel designed for installation in a 19-inch rack. The receiver is a dull metal grey with "panels" of lighter grey where controls of a similar function are co-located for ease of use. When you go to lift the receiver, you expect a hernia. Surprise! The receiver is actually very light (around 6 kg). It has very readable, and "large" LEDs to indicate the frequency to which it is tuned, right down to the one Hertz level. The tuning increments can be changed from the one Hertz to the one Megahertz level merely by depressing a button. The appropriate LED in the frequency display blinks between two intensity levels to indicate which level you have selected. A single touch (on/off) will toggle you between the "locked" and tuneable choices. When "locked", a green light on the "tune lock" button is illuminated. Accidentally hitting the tuning knob or inadvertently pressing an increment button on the keypad will not change the frequency.

 

Tuning

The tuning knob is large, and relatively light to the touch. The receiver can be tuned by entering a frequency using the keypad. Once tuned, you can change frequency at the increment level indicated by the blinking LED by using the tuning knob or depressing the up or down arrow key on the keypad. Frequency coverage is between 5 kHz and 30 MHz. and there is no doubt that it actually performs across this broad spectrum. Other receivers advertise this capability, but the HF-1000 actually delivers.

The receiver, allows the user to switch between the following modes:ISB, USB, LSB, CW, FM, SAM, and AM.

There is no "RTTY" or "FAX" mode as such. For RTTY you need only set the receiver's BFO offset to +2210 Hz, for FAX +1600 Hz. While the EPROMS for the receiver are easily changed, be certain to ask for the latest version. The version of EPROM is displayed on the front panel's MODULATION/BW LCD display when you turn the receiver on, so there is no doubt as to what version you are running.

 

Bandwidth Choice

The 59 IF bandwidths may present a bit of a problem at first. You select a bandwidth by depressing an IF BANDWIDTH button and then rotating a knob.

When you first turn on the receiver you may go into shock when you find only a small portion of these bandwidths appear to be working! This is because the user is given the option of selecting which BW modes to engage. This requires you to punch the SPECIAL FUNCTION button (repeatedly) until the IF BW selection LCDs indicate you can start selecting which ones are to be activated. While this then becomes a simple toggle operation, it is NOT a user-friendly operation the first time you use it. But after some days of regular use this operation is actually quite logical.

We will go into the performance of these bandwidths later in this review. Suffice it to say, unless you like to turn knobs, you will soon reduce the bandwidth options to those you find most useful for the type of listening you do. In the ISB, USB, and LSB modes your options are limited to a far smaller subset of the 58 bandwidths available.

The BFO is adjustable in exact 10 Hertz increments between minus 8,000 Hz and plus 8,000 Hz. We set it up to switch between +750 Hz, +2210 Hz and +1600 Hz for CW (Morse code), RTTY, and FAX respectively. The 750 Hz setting is optimal for the CW decoders such as the Universal M-7000/M-8000 series.

 

Notch Filter

There is also a "notch" filter that uses the "BFO" button(s). It is used to eliminate those heterodynes that can drive you crazy while listening to a signal being interfered with by another signal. Also there's a 10 step "blanker" which is just right for eliminating the likes of ignition and other "spike" noise.

We will not go into any further detail on how the myriad of controls function, or the methods required to use them. Suffice it to say that it may prove a bit confusing at first, but that there is a real consistency in approach to all receiver operations. Once you are used to it, it is remarkably easy, although sometimes tedious, to use.

Other operational features include computer control, a preamplifier, and attenuator mode, and various scanning modes. The scanning modes allow you to scan and dwell between two frequencies in increments you set, and to scan between two user selectable channels of the 100 available for preset in memory. You can lockout channels and frequencies, select tuning intervals, pause as you scan, etc. Obviously the user can customise receiver operation to a very large degree.

Other features of the receiver are dual 455 kHz IF outputs (one filtered, one not), audio via a D-type pin, RS-232C and CSMA computer control inputs, and an external reference (5 MHz) input for use with a frequency standard (Rubidium, in the test case). The antenna connector is a BNC female, and connecting to a "standard" longwire or PL-259 plug terminated antenna requires an adapter.

 

Performance

Among the most important features of a top-level shortwave receiver are: sensitivity, stability, selectivity, audio quality, ease of operation and features. The HF-1000 certainly is as sensitive as the other high end receivers. It also has an accurate, and meaningful, signal strength (analogue) meter which tells you the signal strength in dBm.

The stability of the receiver certainly seems well within the plus/minus 1 part per million claimed. During the tests in the USA, Tom Roach felt this was not adequate, so he locked the receiver to a Rubidium "atomic" standard. When he first received the receiver the tuning accuracy was "terrible" (i.e. just within the 1 PPM advertised). He found that the receiver was 5 Hz off the mark when tuned to WWV at 5 MHz! As it turned out, this was easily rectified by removing the top panel of the receiver and adjusting the "R59" potentiometer (the only user adjustable "maintenance" control). Of all the WJ owners we have corresponded with, this was the only one that required this adjustment.

 

Selectivity

In terms of selectivity, in both the number of bandwidth options available and the "shape" factors, the HF-1000 has left the competition in the dust. From talking to other users, most claim that what you hear in 2.6 kHz bandwidth on the HF-1000 sounds like what you hear on a non-DSP receiver at, say, 3.2 kHz. This apparently results from the excellent shape factors and decreased distortion which results from well executed DSP algorithms. DSP determines both the shape factor and quality of audio and these are inseparably related.

In all the A/B tests performed against a variety of "top level" receivers, the HF-1000 was capable of producing understandable audio on AM signals (DX) which were inaudible on the other receivers.

Another important feature to many shortwave listener's is "audio quality". A quick look at the audio output on an oscilloscope showed the audio to be severely clipped. Decrease the RF gain and the clipping disappears. With ionospheric disturbances, distortable E and H wave colliding and raising the dickens with almost all shortwave signals, the question of audio quality is somewhat moot. But there are obviously those who feel otherwise. If this is an important issue to a would be buyer, we can't recommend too highly that he (or she) purchase the receiver with the vendor on the understanding that the receiver can be returned. The tuneable notch heterodyne killer is spectacular "audio improver".

 

Minus Points

There are some very real shortcomings associated with this receiver. The learning curve seems a bit too stiff, the bandwidth and other small tuning knobs should be continuous; then turning from the upper limit to the lower limit of your 59 bandwidth settings doesn't wear out your wrist or the knob! The AM sync isn't selectable, as it is in the Sony ICF-2010 (ICF-2001D) of ICF-SW-7600G. The instruction manual was apparently written for the government or by a technical writer fired from his previous job writing inscrutable operating instructions for a VCR.

The D-type plug should really be provided already wired and colour coded so you can easily tap to the audio output you want.But it is not! Tom Roach believes a lot of the reported problems with the HF-1000 audio is due to the use of the "D" plug. He uses the output from the front panel headset and seem to have avoided all the problems. Tom always observes the output of the audio on an oscillocope and has no distortion except if you overdrive it in the "manual AGC" position. The 1997 Passport to World Band Radio still makes the claim that the receiver needs a "balanced" or at least shielded antenna. At least as far as our experience goes,this is not needed. Once again Tom Roach has some indications that this may be the case if you use that "D" connector. He made many an A/B test on weak signals comparing a JRC NRD-525 with the WJ-1000. For whatever reason he could clearly hear signals on the WJ that were lost in the noise on the NRD-525.

 

The WJ-1000 in Europe

We looked at the receiver through different eyes because the receiver is considerably more expensive in Europe (around US$9000 at most dealerships, although we were quoted around £5000 in the UK). The cost is linked to import duty. You could import the set directly from the US, but note that repairs can only be carried out by Watkins-Johnson themselves. None of the dealers in Europe have the equipment to do repairs themselves. At the price quoted, the HF-1000 is in the same category as the Rohde and Schwarz EK 890 and three times the price of the NRD-535D.

 

Digital Reception

Many people are familiar with the compact disc. Sound is stored on the disc as a series of digits. In general, digital processing of that compact disc sound is regarded as providing a much better audio quality in medium and high cost hi-fi sets. Yet there are still some people (with golden ears) who claim that high-end analogue amplifiers sound better than digital ones. That same analogy applies to the new generation of receivers like the WJ HF-1000.

The compact disc is a digital source. But the long wire antenna delivers hundreds of thousands of analogue signals between 9 kHz and 30 MHz. The strength varies from one microVolt to several milliVolts, out of which the listener wants to pick just one signal.

Technology has not yet reached the point where this whole range of signals can all be sampled and processed digitally. In the HF-1000 front end is therefore analogue. It starts with a 32 MHz low pass filter, followed by a high level mixer which converts the signal the first IF stage at 40.455 MHz. That brings with it a problem. The standard version of the HF-1000 has no bandpass filters to limit the number of signals presented to the first IF mixer. That can lead to 2nd order mixing products if too much signal is present. Although the 2nd order intercept point turns out to be +60 dBm, it is not enough if you connect a decent passive or certainly an active antenna and use the HF-1000 in Europe. The signal levels are very different to those monitored in the Pacific and North America. Watkins-Johnson makes a sub-octave pre-selector for the HF-1000 for US$600. This is essential if you use the set in Europe and demand the same specifications as listeners elsewhere. Without it we found overload problems from the 7 MHz broadcast bands when using longwire antennas in the region 14200-14400 kHz.

The first IF mixer has a bandwidth of 30 kHz, on the wide side for a professional receiver. That is room enough for 6 shortwave broadcast stations and several dozen utility stations. This broad range of signals is then sent through a variable attenuator (this ensures a constant signal level that is essential when the signal is converted from analogue to digital at a later stage). From the attenuator the signal goes into the 2nd mixer which downconverts the signals to 455 kHz. This second mixer is also broad, around 25 kHz. Finally, there is a 3rd mixer which downconverts the signals again to an intermediate frequency of 25 kHz. So there are three analogue mixing stages before the digital processing begins.

 

Digital section

We have to over-simplify the next stage in the process, but still. The 25 kHz wide segment of analogue signals is now put into an analogue to digital converter. That measures the strength of the incoming signals no less than 100,000 times a second and changes this into a stream of numbers. The HF-1000 uses an A/D converter which changes the IF signal into a 32 databits, of which 16 are used to describe the signal. So now it is possible to process the signals mathematically. Take the squelch for instance. This is digitally adjustable from 0 to -135 dBm. Suppose we want to set the level at -107 dBm (i.e. one microVolt). When we set that the microprocessor is instructed to only let signals through that have a number corresponding to -107 dBm or higher.

The HF-1000 offers 59 bandwidths from 56 Hz to 8 kHz. The conversion process happens at a fixed rate, namely at 100 kHz, so the process not only registers the strength of the signal but the frequency too. Since the digital stream from the converter contains this information, you can instruct the microprocessor to only allow signals through between certain frequencies. That's why the shape factor of the filters is almost ideal. There are some compromises because you're not dealing with a single signal but a bandwidth of 25 kHz.

 

Digital filters

Digital processing has another advantage. In a standard quartz IF filter there is a problem with time-lag. Higher frequencies do not travel through the material at the same speed as lower frequencies, leading to the so called "ringing effect", i.e. a form of distortion. In utility transmission systems like RTTY this can lead to an unreadable character at low signal levels. The digital filtering doesn't have this problem... signals are processed at the same time.

But digital technology is not perfected yet. Microprocessors are not yet fast enough that they can sample the signals at 40 MHz. That's why there are three analogue mixing stages to bring the signal down to a point where a/d conversion can take place. The first IF is very high quality, but cost limitations mean that the 2nd and 3rd stages are a compromise. It is in these stages that 3rd order intermodulation products can be produced.

There are also limits on the dynamic range. The a/d converter uses 16 bits to describe the analogue signal. There's a simple formula that says that the maximum dynamic range is therefore 6 times the bit-rate minus 1. For the HF-1000 (and a compact disc) that works out at 95 dB. That is fine for a CD but it is not quite high enough for a communications receiver in the professional class. High quality analogue receivers with low-noise synthesisers, high level mixers and quartz filters can reach this level of dynamic range with ease. Watkins Johnson has had to design a very rigorous AGC system to ensure that the A/D converter is not overloaded. If signals don't fit inside the 95 dB "window" the result is terribly distorted audio. The AGC range in the HF-1000 is 100 dB, and an amplifier/attenuator combination in front of the first mixer also ensures the signal can be controlled between +10 to - 15 dB.

During our listening tests in Europe we listened to the marine bands to telex-over-radio signals close together. If you set the bandwidth so that only a very weak TOR signal gets through then the receiver's AGC opens up to maximum sensitivity. The strong nearby signal can then sometimes overload the A/D converter. The same problem can occur with analogue sets of course, but they are not so critical. In future, digital receivers will probably switch to 24 bit a/d converters, whereby the dynamic range will be 143 dB... no problem. Likewise, faster processors will eliminate the need for analogue mixing at the front end. What Watkins Johnson are introducing now is just the tip of an iceberg. Hopefully we will see more DSP in consumer radios before long.

 

Measurements

Radio Netherlands uses a standard laboratory measurement technique developed by European PTT's. That allows readers to compare receivers in similar price categories knowing they have all been through the same stringent testing procedure. In addition we use the receiver in several locations (city and country) to see how the theory matches the practice. It is clear though that standards for digital receivers will have to be developed. You can use the specifications developed for analogue receivers to measure sets like the HF-1000. But the digital signal process also generates new audible effects for which international measuring standards have not yet been defined. That means that for the time being some of the effects described by reviewers are based more on listening experiences than measurement.

Our tests in Europe involved a HF-1000 compared against an NRD-535D. Even though the sensitivity figures of the HF-1000 look only fair on paper, we only needed 10 dB pre-amplification above 25 MHz. The squelch on the HF-1000 is accurate but doesn't have hysteresis... that's sometimes annoying during a deep fade. We also trawled through the 49 metre band in the European evening, selecting a weak station wedged between two powerhouses. You can reduce the bandwidth step by step to a point where the speech becomes so muffled that it is only just intelligible. We found instances that on the HF-1000 the side-splatter was noticeably more annoying than on the NRD-535D with the same bandwidth using crystal filters. Yet there were also occasions (during the day listening to Asian stations on the tropical stations) when the HF-1000 was clearly better.

 

Conclusions

The Watkins-Johnson HF-1000 is the window on tomorrow's technology. If you're willing to pay the price you can have a front row seat. The company are open about the fact that this receiver is "work in progress". Being digital the advantage is that an upgrade simply involves changing chips. In November 1994 upgrades were released to give additional bandwidths for 3.6 and 4.0 kHz in the USB and LSB modes and there were further upgrades in 1996.

Mike Cox, senior applications engineer at Watkins Johnson has gone out of his way to ensure that users of the receiver are kept up to date with new developments and they seem to take feedback seriously. The HF-1000 is not a beginners receiver and what you get out of it depends on where you are listening and what antennas you use. If you're going to pay this kind of money take some time to do some research... above all listen to what you're getting.

This review first appeared on the Radio Netherlands website.