Comparing the Watkins-Johnson WJ-8711 & WJ-8712 with TEN-TEC RX-340 & RX-331 receivers

Many thanks to SWLing Post contributor, Paolo Viappiani, who shares the following guest post:

The WJ-8711 & WJ-8712 vs. Ten-Tec RX-340 & RX-331 Receivers

by Paolo Viappiani, Carrara, Italy

In recent years, a renewed interest has grown in regards to the best HF receivers using “first generation” DSPs, typically the HF-1000/HF-1000A, WJ-8711/WJ-8711A and WJ-8712 models by Watkins-Johnson and the RX-340 and RX-331 models by Ten-Tec. Even today, the aforementioned receivers are considered among the best performers of all times; this is a well-deserved fame in the case of the W-Js, a bit less with regard to the units manufactured by Ten-Tec, a firm that once had a good reputation but that has been recently acquired by a new owner (who sold the old facilities by transferring the company and distorting the sales, support and assistance policies of the previous company [2]). I therefore believe that this article serves as a dutiful information for the readers who are potentially interested in these receivers.

A Bit of History

In the years between the last and the present century, two receivers very similar to each other in terms of design and structure were released almost simultaneously by Watkins-Johnson of Gaithersburg, Maryland [1] and by Ten-Tec of Sevierville, Tennessee [2]: the WJ-8711 (later upgraded to the A and A-3 versions and followed for a short period by the HF1000 and the  HF1000A  “civilian” versions [3]) and the Ten-Tec RX-340; both of them are shown in Figure 1.

Figure 1: The WJ-8711A (above) and Ten-Tec RX-340 (below). Notice the similarity of the front panels of the two radios.

The WJ-8712/WJ-8712A and the Ten-Tec RX-331 receivers were released by their respective manufacturers in that period also (the latter one was preceded by the RX-320 and RX-330 models). All these types were nothing more than “black-box” units, that in all respects corresponded to the WJ-8711A and to the Ten-Tec RX-340 receivers but that had not been provided with true front panels, as they were controlled by special hardware interfaces or from a PC, look at Figures 2 and 3.

Looking at the appearance of the WJ-8711/HF1000 receiver series and of the Ten-Tec RX-340 units, a relative similarity to each other is evident, and it has led to various speculations regarding the design of both devices.

One of the theories was revealed by James (Jim) C. Garland W8ZR of Santa Fe, New Mexico [4], about which he claims to have obtained information from a Ten-Tec employee directly. James claims that in 1991 the US Government Agency NSA (National Security Agency), which used to purchase numerous HF receivers for surveillance and interception, decided that the current cost of the receivers were too high and formed a special group in order to study how to obtain a possible price reduction.

At that time the high-end HF receiver market was dominated by a few manufacturers: Watkins-Johnson, Racal, Cubic, Rockwell-Collins and a few others, and Ten-Tec applied for joining the group.

Figure 2: The WJ-8712A (above) and Ten-Tec RX-331 (below). While the Watkins-Johnson model is two rack units high and half wide, the Ten-Tec develops less in height (only one rack unit) and more in width (standard 19” rack). However, both receivers are quite deep (more than 20”-50 cm.).

Figure 3: The Tmate unit of the WoodBoxRadio is shown here; it is one of the possible accessories which, together with a PC monitor, allow using the “black-box” receivers via an RS-232 interface.

According to the information provided by Jim Garland, the Watkins-Johnson and the Ten-Tec designers worked together for about one year in order to agree on the technical characteristics and guidelines of the “radio of the future” which must meet all the requirements that the NSA requested.

The team eventually agreed on a common set of specifications to submit to the Government Agency, while both Watkins-Johnson engineers and Ten-Tec colleagues, who were expecting  a consistent number of orders, worked hard in order to develop the technologies necessary for the production of this new “breed” of radios. At the last moment, however, it seems that Watkins-Johnson, to Ten-Tec’s great surprise and dismay, requested that the NSA added an additional specification: an MTFB (Minimum Time Between Failure, i.e. minimum interval between two subsequent failures) of 10,000 hours, a stringent requirement that was normally required for aerospace electronics only. Such a step constituted a real spite on the part of Watkins-Johnson, which had a substantial and more than a decade-long background of military and aerospace government supplies (in particular of telemetry receivers): at this point Ten-Tec, with its experience carried out solely in the field of amateur and consumer electronics certainly could not meet the new requirements.

Ultimately it seems that the latter gave up participating in the bidding process and that Watkins-Johnson won the contract for the supply of the new radios. And James goes on by asserting that, in the absence of competition, Watkins-Johnson was able to sell their WJ-8711s to the NSA at a much higher price than initially expected. Ten-Tec’s reaction, however, was not long in coming: the Sevierville company quickly introduced its RX-330 model (almost immediately followed by the RX-331), a “black-box” receiver without front panel and controllable via RS-232 interface which, despite not meeting the MTBF specification, was an instant success both at the NSA and at the agencies of other countries; this was also due to the fact that the Ten-Tecblack box” was sold for about a third of the price of a WJ-8711/8711A receiver.

After this success Ten-Tec decided to release also the RX-340 model, as a direct competition.

This fascinating story by Jim W8ZR raised doubts and objections by Paul S. Courson WA3VJB and others (see also note [4]).

Another version of the story (where Ten-Tec is not mentioned however) is the one that was written by Rick Lober, a former Watkins-Johnson employee and that was also published on the Facebook group “BlackRadios” [5]. In short summary, according to Rick, around 1990 one of Watkins-Johnson’s largest Government customers asked if it was possible to design a high-performance HF receiver (similar to the well-known WJ-8718, which at the time sold for about $15,000-18,000 [6]) but with a cost closer to that of the ICOM units they were purchasing but were not totally satisfied with. The proposed target was a unit price of $3,000 for 1,000 units which would be purchased immediately after an initial order of 6 receivers which, however, had to be delivered within 9 months.

Bill Bruff, at the time Watkins-Johnson’s Division Director, accepted the challenge and formed a dedicated design team, headed by Steve Hedges; Rick Lober himself was part of that team. According to Rick, the only way to achieve the cost objectives was to use a DSP-based IF and detection section, that had been already used a few years earlier by Rockwell-Collins but that turned out to be problematic due to the power required and the heat developed. In the meantime, however, the technology had advanced and it was finally possible to think of a radio consisting of a fairly conventional RF section followed by an A/D converter and a DSP in which all the functions usually elaborated by analog circuits in the receivers were implemented. The RF preselector had to be optional (as in the WJ-8718 receivers) and the rest of the unit had to include a switching power supply and, of course, a front panel with all the controls and the large tuning knob that was characteristic of the W-J receivers. The W-J team worked day and night to refine the project and to solve the problems that gradually arose, and this also happened the night before the presentation of the first 6 prototypes to the customer. In this regard, Rick reports that: “The team returned home around 6 in the morning, took a shower, put on a tie and showed up at 9 to meet the client. Three hours later the six units had been sold, despite the persistence of some small problems.”.

In later times the 1,000 units that had been initially agreed on were also sold and other configurations were developed, in particular the WJ-8712 and 8712A models (both with a “blind” front panel and PC controllable) and a “consumer” version called HF-1000 and HF-1000A, mainly intended for shortwave listeners.

Which of the two versions of the “history” to believe? Even Terry O’ Laughlin, one of the world’s leading Watkins-Johnson experts [7], which I asked some time ago, confessed to being very doubtful about it; so, after hearing various other sources, I got a certain idea… Indeed:

1) It is unreasonable to think that two receivers so similar to each other were developed and released almost simultaneously without any contact between the two design teams;

2) Neither Watkins-Johnson nor Ten-Tec have ever mentioned any mutual collaboration, nor have they replied, when asked, on the specific topic. I therefore think that there has been some form of “industrial espionage” by one or more people of the two teams, and that the thing has been hushed up in a hurry, having involved Agencies and Government projects. This, however, not without having given some “sop” to both manufacturers: to Watkins-Johnson by assuring them good sales contracts on the WJ-8711 and 8711A units, to Ten-Tec by accepting substantial supplies of their “black-box” radios RX-330 and RX-331.

Should this have been the case, even the similarity in the front panels of the first DSP receivers of the two different manufacturers would not be accidental at all, being the result of a collaboration that was prematurely interrupted for various reasons… the Military-Government market has always appealed to everyone and is well worth an under-the-table deal!

Features of the WJ-8711 Series (WJ-8711&A, WJ-HF1000&A) and of the Ten-Tec RX-340 Series Receivers 

This article mainly concerns the “direct use” receivers, i.e. it does not consider the “black-box” versions that can be used and controlled via PC and/or by special interfaces (explicit reference will be made to them only when necessary). So let’s take a look at their technical characteristics first, then moving on to their construction and to their own particularities.

Both the Watkins-Johnson’s8711 Series”/“HF-1000” receivers and the Ten-Tec’s RX-340 are classic solid-state “triple conversion” units, with continuous frequency coverage from 5 kHz to 30 MHz (but tunable from 0 Hz) and with a frequency resolution of 1 Hz.

All the receivers show a fairly conventional RF section that is followed by a “DSP section” in which the signal is processed both for what concerns the bandwidth and the demodulation, as well as additional features such as Noise Blanker, Pass-Band Tuning, Notch Filter, etc.

In the Watkins-Johnsons the first conversion is managed by a first synthesized local oscillator, driven by a very stable 10 MHz frequency reference and generating frequencies from 40.455 MHz to 70.455 MHz in 1 kHz steps, which leads to a first IF of 40.455 MHz. The signal then passes through a filter with a bandwidth of about 30 kHz, then a second and a third synthesizer (always driven by the same reference at 10 MHz) properly inject signals at frequencies of 40 MHz and 430 kHz for the purposes of obtaining “intermediate frequencies” at 455 and at 25 kHz.

A 455 kHz output is present on the rear panel of the radios (for connection to a spectrum analyzer or for other uses), while the 25 kHz signal is digitized at 16 bit with a 100 kHz sampling frequency and sent to the “DSP” for subsequent signal processing.

The signal management carried out by the Ten-Tec RX-340 takes place in a similar (but not identical) way: after the conversion to the IF value of 455kHz, there is a further conversion (this time not at 25 kHz, but at 16,666 kHz instead). After that, also in the Ten-Tec RX-340 the digitized signal is sent to the DSP section for subsequent signal processing, which in both receivers consist of: Noise-Blanking, Fine Tuning with 1 Hz resolution, IF Filtering and band-pass adjustment, Notch Filter, Gain adjustment, AGC adjustment, Level and Squelch indication functions, demodulation in various modes, etc.

Further details about the characteristics and the various differences between the Watkins-Johnson and the Ten-Tec receivers can be better understood by reading the various Data-Sheets and manuals (complete with diagrams), that are available at the addresses that are specified in [8].

As for the reception modes, in practice the ones found in the Watkins-Johnson receivers (AM, Synchronous AM, FM, CW, USB, LSB, ISB) are the same allowed in the Ten-Tec units (although with different practical results, see later); it should also be noticed that the special WJ-8711A-3 version (defined by the company as the “Government version” [9]) also has the FSK mode in addition to various other options (preselector, internal loudspeaker, high stability reference osc.) included.

Yes, because one of the characteristics that differentiates the Watkins-Johnson radios from the Ten-Tec units lies precisely in the fact that while the former were normally supplied in the “basic” version (for which many options were made available, including the internal loudspeaker and the preselector), both the RX-340 and the RX-331 came already “complete with everything” and for them there were no options available to be purchased later.

The various functions of both the receivers are controlled by software contained in three distinct EPROMs: one relating to the “Front Panel Functions” (U3 in Watkins-Johnson receivers, U4 in Ten-Tec) and the other two for “Processor Control” and “DSP Functions” (U12 and U56 in Watkins-Johnson receivers, U12 and U30 in Ten-Tec units respectively).

Furthermore, when you turn a Watkins-Johnson receiver on, the lower small display in the mid of its front panel shows the firmware version of the “Processor Control” (U12) EPROM only, the firmware versions of the other EPROMs (U3 and U56) can be checked by reading the label sticker on top of each IC.

In the Ten-Tec RX-340 receivers the firmware versions of each of the three EPROM (U4, U12 and U30) are all displayed for a while in the two alphanumeric displays that are located in the mid of the front panel, each time you turn the receiver on.

In the first series produced by Watkins-Johnson, the task of maintaining the various data (memories, etc.) with the receiver off was entrusted to a “coin cell” battery (visible in Figure 6 for what concerns a “first generation” WJ-8711), that was later replaced by “Timekeeping RAM” ICs (DALLAS-MAXIM “DS1643-100+” or STI MICROELECTRONICS “M48T08-150PC1”.

In the Ten-Tec units, on the other hand, a lithium battery enclosed in an IC has always been used (STI MICROELECTRONICS “M4Z28-BR00SH1”, Figure 9). Obviously the receivers of both manufacturers are equipped with the “BITE” diagnostic function, as well as selectable RF preamplifier and attenuator. In order to compare the main characteristics of the Watkins-Johnson receivers with those of the Ten-Tec units, in Figure 4 a summary table of the main operating parameters is shown.

Some Notes About Accessing the BITE Functions

In the WJ-8711: Press the front “Special Function” button until the message “BITE Pending” appears on the display. Then turn (in either direction) the knob that is placed above the button; the 16 BITE tests begin and all front LEDs light up.

The results appear in the receiver display as a decimal number equivalent to a 16-bit binary and are explained in Table 3-2 of the WJ-8711A Manual (pages 3-47 and 3-48).

In the Ten-Tec RX-340: Press the left and right arrow keys of the Mode Select control together, then at the prompt “Enter BITE Level” type 1, 2 or 3 on the numeric keypad in order to choose from the three possible BITE levels you want and start it. More details are found in section 5-7 of the RX-340 Instruction Manual (page 5-11).

Figure  19 shows the WJ-8711 (left) and RX-340 (right) BITE screens.

Constructional Details 

Both the Watkins-JohnsonWJ-8711 series” receivers and the Ten-Tec RX-340 are housed in metal cases with standard rack dimensions for the front panels (19” – 48.3 cm width,  3 rack units height – 13.4 cm), but they have very different depths: the former are about 20” – 51 cm deep (I would say uselessly), while the RX-340 has a more reasonable depth of about 12.5” – 32 cm.

The weights are comparable: 6.8 kg for the “basic” Watkins-Johnson models, 5.7 kg for the Ten-Tec RX-340. The cabinets of both receivers are undoubtedly well built (the “gold” anodizing of the Ten-Tec chassis is very pleasing), but undoubtedly their sturdiness is inferior to that of other “non-DSP” professional receivers (to name a few ones, the “old” WJ-8718, the RACAL receivers, etc.). Even the front panels, that are built in aluminum and are covered with a glued tactile plastic film (which will hopefully get ruined as late as possible) do not give the impression of being in front of professional receivers, in fact it seems to be dealing with some consumer unit…

Figures 5 to 11 show the internal constitution of the W-J Series 8711 and of the Ten-Tec RX-340 receivers, while Figure 12 refers to the internal structure of the “black-boxRX -331, in my opinion of a bit exaggerated depth. It should be noted that the RX-331 is, from a circuit point of view, very similar (but not identical) to the RX-340 and it does not have an internal loudspeaker.

Further clarification is appropriate here: both the Watkins-Johnson and the Ten-Tec units are equipped with well-built switching power supplies: the one that is fitted into the WJ-8711 Series receivers is of the Condor brand (model SP1348A, manufactured in Mexico), the one that is used on the Ten-Tec RX-340 radios is of the Philhong brand (model PSA4541, manufactured in China).

As it will be highlighted later, both the power supplies are not free from some problems however.

Operation and Various Tests 

Even if the main purpose of this article is not to report the results of the operational tests of the different receivers by comparison, but rather to highlight the various idiosyncrasies found and to provide opinions and advice on the matter, it is still advisable to briefly address the issues.

I therefore specify that both myself and my friends Mauro Trazzi IZ1GCX of Arizzano (VB, Italy), Ralph Menn of Saarbruecken, Germany and two more users from center Italy proceeded, in a totally independent way, to carry out repeated and prolonged listening tests using both their WJ-8711As and their Ten-Tec RX-340s in various working conditions (which, not being “standardized”, have no absolute value but still represent shared impressions).

Figure 5: WJ-8711A internal view (front panel PCB seen from the rear). In this shot you can see the empty space inside the receiver. Also notice U3, the front panel EPROM.

Figure 6: Internal view of an early-version WJ-8711 and of its component parts, including the “Condor” switching power supply, the optional preselector and the two EPROMs U12 and U56.

Figure 7: Location of the Timekeeping IC in a later generation WJ-8711A. Also note the power connector, which is sometimes a source of problems.

In short, we all five “testers” found ourselves in almost a complete agreement with each other and with what emerges in the reviews of the two receivers published by the well-known David W. Zantow N9EWO [10]: the Watkins-Johnson WJ-8711A shows top performances on most fronts,

even in synchronous AM detection (mode in which it operates only in double sideband, while the Ten-Tec RX-340 allows sideband selection but shows poor results due to the continuous loss of the “lock” condition).

Excellent are the results obtained by the use of Pass-Band Tuning and of the Notch Filter in the Watkins-Johnson receivers, which also widely outclass the Ten-Tec RX-340s in terms of processing and weak signals reception. Luckily enough, none of us was faced with a fairly frequent problem that had shown in the Ten-Tec RX-340, namely the main fluorescent display (Samsung brand) that was used in early units and had segments not uniformly lit (as it was reported in the N9EWO review [10]); however, both Mauro and myself (and unfortunately other friends) have come across other problems that were not easy to solve, see below.

Figure 8: This is the rear of the Ten-Tec RX-340 front panel: notice the Philips CPU and the U4 EPROM.                                    

Figure 9: The battery IC of the Ten-Tec receivers (Data-Sheet at:

Figure 10: The upper part of the Ten-Tec RX-340 frame shows a rational use of space and the achievement of a more contained depth for the unit. Note also the two EPROMs U12 and U30.

Problems Found in the Receivers

Watkins-Johnson WJ-8711A: no problem emerged from Mauro’s unit, from mine I had only a problem with the master volume potentiometer of my WJ-8711A-3 leapt out, but probably it was caused by dirt (the issue was promptly fixed by applying a few drops of Deoxit-5).

From Ralph’s side some problems emerged in the Condor SP1348A power supplies of three of the WJ HF-1000/WJ-8711A units he had on the bench and he was compelled to repair them; the problem was caused by electrolytic capacitor failures however. The acquisition of some of those caps can be a challenge nowadays.

About the W-J power supply, Ralph declares that it is very low in noise and that he was not able to find any additional switching noise in the spectrum; when that PS works properly, it stays quite cool during operation. The only noise that can he heard from the W-J receivers seems to be solely an audio problem: it sounds like a high RPM fan in the power supply section, but the WJ’s power supply is fan-less!

Ralph also says that he never heard (either directly or from any other Ten-Tec user) about RX-340s  having the same kind of problem with their Philhong power supplies: there are no strange noises that are emitted into the room indeed.

Ten-Tec RX-340: with these receivers the problems that arose were are more serious and certainly they were due to poor checks carried out at the factory. Starting from Mauro’s unit, it should be immediately noticed that his Ten-Tec RX-340 (S/N 10227) had been showing intermittent operation for some time, and that the BITE was continuously indicating problems with the 1st mixer (so that IZ1GCX had also proceeded to purchase an RX-331 in order to use it as a possible source of spare parts). But after various tests, measurements and observations, Mauro noticed an important detail: one of the two wires was missing from a connector on the “1st Mixer” board (Figure 13).

The problem, certainly due to poor quality control by Ten-Tec, was promptly fixed, and after having added the missing wire (Figure 14) the RX-340 started working regularly. There are no words however! Another issue that was also fixed by Mauro concerns the solderings (ALL were found to be “cold”) of the power supply connector to its PCB, Figure 15; also in this case redoing was decisive, but such defects should not occur in high-class devices!

Figure 11: The lower part of the Ten-Tec RX-340 chassis is shown here.

Figure 12: Was Ten-Tec “infected by the mania for depth”? Here is the inside of the RX-331, a slender “beast” 21”-53 cm deep. Question: couldn’t the height of the unit be doubled and its depth halved? Hmm…


Figure 13: The photo shows the connector without one of the two wires in Mauro Trazzi’s RX-340.

Figure 14: The “repaired” connector with the addition of the missing wire.

Figure 15: The “cold” solderings in the Ten-Tec RX-340 power supply connector

As for me, I found my RX-340 (S/N 11194, that worked well after a thorough cleaning of the volume pot by applying some drops of Deoxit-5) plagued by a problem that was found to be common to other RX-340s: the two EPROMs of the DSP-CPU printed circuit (U12 and U30) were found not removable from their sockets, as if they had been glued or fastened in some way.

After several attempts with many types of IC extractors I preferred to give up, for fear of damaging those precious EPROMs; for sure I will try again in the future, as I promised myself to copy the related software and make it freely available to anyone who needs it; as I already told, the same situation had showed up both in the RX-340s owned by two other hams in central Italy (who still prefer to remain anonymous) and also in the Ralph’s unit (S/N 11341). Another drawback found in the Ten-Tec receivers consists in the application of useless “warranty tags” (what type of warranty?) which discourage the user from performing sometimes useful operations, look at Figure 16.

Figure 16: A warning tag applied by Ten-Tec.

Other comments:

About the HF-1000s/WJ-8711s Audio Buzz: Ralph also noticed that all the three units he had at  hand were characterized by a quite disturbing noise coming from the  loudspeaker (just as having a fan running). This annoying noise seems not to come from the power supply, it seems to originate from the processor board instead.

Incidentally, the Ralph’s RX-340 does not show such an audio problem.

HF-1000/WJ-8711WJ-IF filter settings: As already noticed, the HF 1000 model lacks some of the IF filter frequency options  compared to the WJ 8711 & WJ-8711A, but they can be retrofitted by using U12 IC version 4.01.10 and U56 IC version 4.02.07.

Doing so, the HF1000 can now make use of the 16-kHz selectivity setting too.

The Ten-Tec RX-340 does not have the same amount of IF filter options, but it has a 16kHz filter setting as standard.

It’s worth saying that in the W-J line of receivers, the ones fitted with the preselector are the most sought after (and the most expensive because it was a costly option), while all the  TenTec RX-340 receivers already have a preselector built in.

Assistance for the W-J “8711 Series” Receivers and for the Ten-Tec RX-340 and RX-331 Units 

Unfortunately, while some source of assistance is still active for the Watkins-Johnson units [11], nothing similar exists with regard to Ten-Tec receivers, for which it is practically impossible to obtain neither assistance or spare parts from the parent company nor the firmwares that are needed for restoring or updating the existing ones.

In recent times, Ten-Tec has “closed up” and does not seem to care about assisting old customers; the latest somewhat “aberrant” press releases are reproduced in Figure 17.

If a “markup” of $140 (plus shipping costs) seems to be right whether your apparatus is repaired or not…

So what can you do? First of all, keep your fingers crossed and hope that your receiver (both Watkins-Johnson and/or Ten-Tec) never breaks down; as a second instance, hope that any eventual failure involves parts that can be usually found and can be managed by good servicemen (there are good ones all around the world, believe me).

If, on the other hand, the fault involves the EPROMs and their firmware, Watkins-Johnson owners will be happy to know that I recently uploaded the latest WJ-8711A receiver firmware in the “file” section of some Internet groups [12].

However, I hope to be able to do the same with the Ten-Tec receiver software in a fairly short time.

The very latest information given on the Ten-Tec website is dated from Nov 2022, so at least somewhat recent, but it specifies only that “there are some counterfeit press releases on social media” (look at Figure 20) and there was no more update.

About the current prices of the WJ-8711 Series and T-T RX-340 receivers, they can be sometimes found on the surplus market, but their prices depend also upon the completeness, the conditions and the age of the units. I.e., a bare WJ-8711 or HF-1000 without the preselector, the speaker and other options but in good enough condition can be found at around $1,300 (1,200 Euro), but if you want a recent, like-new and complete unit the  prices are as high as about $3,500 (3,000 Euro) or even more.

Please notice that in October 2019 I paid about $3,000 (Euro 2,800) for my WJ-8711A-3 S/N 37 (this Serial Number is very late for an A-3 version, see text) in like-new condition and complete with all the specified options (preselector, high-stab oscillator, speaker, FSK mode).

On the other hand, a Ten-Tec RX-340 is a more rare item and it is highly priced consequently. But again it depends from the conditions and the age of the units: i.e. a unit in fair conditions and with the V1.10A firmware costs less than a VG unit with the V.10B firmware (and, as far as I know, it is currently impossible to find copies of the software in order one can update the EPROMs!).

Usage Tips 

Based on my experiences and those of other users, here are some tricks that could be useful when using the W-J “8711 Series” and the Ten-Tec receivers:

– Before turning on the units for the first time, check (and if necessary clean) the contacts of the output conductors of the power supplies (multi-pole connectors and relative soldering to the PCB);

– Activate the BITE functions and wait for the response (hope no error is found); otherwise examine the section where the problem occurs. With regard to Ten-Tec receivers, bear in mind that the BITE function should only be activated about an hour after switching on the radio and without connections to the antenna and headphone sockets (Figure 18).

Figure 17: One of the latest press releases from the new Ten-Tec property.

Figure 18: Instructions provided by Ten-Tec regarding the RX-340 “BITE” function.

– If the receiver memories do not contain important data, carry out a “reset” to the factory settings. In the W-J receivers, this is obtained by holding down the “CE” (Clear Entry) key when switching the radio on, releasing it immediately afterwards; in the Ten-Tec RX-340 the procedure is almost identical, but the key to be pressed at start-up (and then to be released) is the “C“.

– Check the firmware of the radios (and if possible update it to the latest version available, suitably replacing the EPROMs of the “Digital Assembly” (W-J) or “DSP-CPU” (Ten-Tec) boards). Obviously the operation is facilitated in the case of W-J receivers due to greater availability of software files [12].

– Always keep the antennas in use well away from the receivers and check that they are connected using a perfectly shielded coaxial cable in order to minimize the noise picked up by the internal “switching” power supplies;

– Keep the receiver under observation for a certain period, noting any overheating, smell, component blackening, etc.

Figure 19: The “BITE” screens in the WJ-8711 (left) and in the Ten-Tec RX-340 (right).

Figure 20: The latest statement by Ten-Tec (Nov. 2022).

It’s also worth to notice that, due to many Watkins-Johnson changing hands during the years, the WJ-8711A receivers were produced under different brands: Watkins-Johnson, Marconi, BAE Systems (British Aerospace), SIGNIA-IDT, DSR Technologies (DSR Signal Solutions), etc; in Figures 21a/b/c some WJ-8711A Data Sheets of various brands are shown.

Currently the WJ-8711 Receiver Series has been discontinued and the property of Watkins Johnson has been in the hands of a major Italian Defense Company (Leonardo S.p.A. formerly Finmeccanica) since Jan. 2016.

Some notes about the receivers that have survived until now and the WJ-8711A-3 Government Version

As far as I know, the WJ-8711 Series of receivers were produced between May, 1991 and about mid 2007-2009. The latest WJ-8711A in which I stumbled upon is the S/N 8358 of the Signia-IDT brand (look at Figure 22); less than 10,000 units in total should have been produced consequently.

It is also worth noticing that around in about May 1996 a very small production of a special version of the WJ-8711A started; it was also called “Government Version” and named WJ-8711A-3, look at the Data Sheet in Figure 23.

That version included some useful options: the Reference Oscillator, the Preselector, the FSK demodulation mode and the speaker and it is recognizable by the two buttons added on the left of the front panel (look at Figure 24a), that would have served for Direction Finding purposes.

The WJ-8711A-3 “Government Version” was always produced under the “Watkins-Johnson” brand only.

Figure 21a:  A Data Sheet of a WJ-8711A of the BAE Systems brand.

Figure 21b: A Data Sheet of a WJ-8711A of the Signia-IDT brand.

Figure 21c:  A Data Sheet of a WJ-8711A of the DRS Signal Solution brand.

The WJ-8711-A3 was provided with A2 U12 and A2 U56 special firmwares, i.e.:

– A2 U12 (Processor Internal Control): V01.00.03;

– A2 U56 (DSP): V05.00.00,

while the A1 U3 (Front Panel) firmware V1.21 was left unaltered instead.

For the rest, the WJ-8711A-3 “Government Edition” is almost identical in performances to the stock WJ-8711A, even if it is a rare beast and it also carries a separate numbering system: the latest WJ-8711A-3 which I saw is the S/N 41 that was sold on eBay some years ago (look at Figure 25), so I argue that no more than 50-60 WJ-8711A-3 units have been ever produced.

As for the Ten-Tec RX-340, their production years should range from 1991-1992 to about 2004-2007 for the latest units.

In Figure 24b my Ten-Tec RX-340 S/N 11194 is shown complete with its outer metal case [13].

Figure 22: The latest WJ-8711A in which I stumbled upon is the S/N 8358 of the Signia-IDT brand

As the Ten-Tec firmware files seem to be really unobtanium, I am asking to all the willing users who have their RX-340 provided with V1.10B firmware version to remove the three EPROMS (U4 Front Panel, U12 Internal Control and U30 DSP) and to copy them to three files by an EPROM reader/programmer. The three files have then to be RENAMED (not converted!) into .pdf extensions and can be sent via mail as normal attachments; the recipient will have to RENAME the received files into to the original extension in order they can be flashed into new EPROMS and used for firmware updating.

Of course I will refund the time and the work costs of willing users in advance, please contact me at: [email protected]

In the case, I will share the three files FOR FREE and at my own risk and responsibility. Thank you!


Figure 23: In December 1966 a special “Government Version” of the WJ.8711A (named WJ-8718A-3) was released, it was Factory provided with special firmware and some interesting options (see text).

Figure 24a: My WJ-8711A-3 S/N 37 (see text).

Figure 24b: My Ten-Tec RX-340 S/N 11194 complete with a metal case by AllMetalParts Co. UK (see Ref. [13]) .

Figure 25: The latest WJ-8711A-3 which I saw is the S/N 41 that was sold on eBay some years ago.

Figure 26: The SAMSUNG fluorescent display used on some early Ten-Tec RX-340’s (left picture) and the single 7-segment green LED displays (MAN6480) used in the W-J receivers (right picture).

Figure 27: A cheap but very effective EPROM reader/copier/programmer that is easily found on the Internet. It can be used for programming NEW (or completely cancelled BLANK) EPROMs.

Final Considerations 

At the end of this analysis I allow myself to make some personal considerations. If Watkins-Johnson hadn’t been forced to reduce costs and had been able to freely design and build a receiver with the same qualities, sturdiness and reliability as the previous WJ-8718 Series, a device still at the top of the current range of HF receiver would really have been born.

And in my humble opinion, relatively little efforts would be enough: a chassis and a front panel with a sturdy structure (similar to that of the previous W-J models), a conventional and “proper” power supply (certainly of the “non-switching” type and provided with an adequate filtering circuits). Sure, you can’t have everything… but it’s a real shame!

As for Ten-Tec, the manufacturer should certainly be invited to adopt fewer “jealousies” and a much better quality control. However, I am a bit skeptical about the promises and the declarations of the new ownership regarding the production of new devices and the restoration of the assistance functions: too many years have passed in which the site does not show updates and remains in practice in a steady state.

Again, it’s a real shame: the RX-340, once the various highlighted idiosyncrasies have been eliminated, is a nice receiver in appearance and, albeit with slightly lower performances, a little more intuitive in operation than the corresponding Watkins-Johnson unit. What to say then?

Ralph finds it worth mentioning again that albeit the RX-340’s slightly weaker RF performance, the unit comes more complete than the HF1000/HF1000A. Meaning that there is no question if this is the “preselector” version of the radio, as it is often asked on trade shows when a HF1000 or WJ-8711 Series receiver is up for sale.

Also considering that in the RX-340 there is no need for an EPROM swap to get access to a 16 kHz filter and that that radio is always the preselector version, my German friend is convinced that the RX-340 is the more modern and complete package, and that its SYNC-AM Detector is capable of good performances too.

For sure the addition of a Sherwood SE-3 Synchronous Detector (now discontinued) will improve
both receivers performances, but it also adds about $1500 to the bill… but this is another story!

So, even if personally I don’t consider the RX-340 purchase too convenient (unless you find a real opportunity at a low price), I advise those who already own it to avoid any tampering or modification, to keep their fingers crossed and to follow literally what a world-known Italian song by Orietta Berti suggests:

As long as the boat goes…let it go!” (“Fin che la barca valasciala andare!”).

And that’s all for now, good listening!

Paolo Viappiani, Carrara, Italy                                                                 Article V2.5 –  March 2023

References, Thanks and Notices

[1]: Watkins-Johnson was a major supplier of radio surveillance and interception equipment to various government agencies and the military of the United States and NATO countries. More details about the history of the company can be found on the website: After 1999, Watkins-Johnson, which was coveted by various industrial groups (mainly European) due to growing business volumes, was first sold to Marconi, then to BAE System (British Aerospace), then to Signia-IDT, to DRS Technologies (DRS Signal Solutions) and finally, in January 2016, to the Italian company Leonardo (formerly Finmeccanica). Currently W-J is therefore an Italian company that operates in the shadow of the Leonardo S.p.A. Group. The various “changes of hands” also explain why the WJ-8711/8711A receivers are found on the used market today under different brands.

[2]: Ten-Tec (abbreviation of Tennessee Technologies) is a company that has produced various equipment for radio amateurs over the years (among the many models we must certainly mention the Paragon, Omni, Argonaut, Patriot transceivers, the ETO Alpha amplifiers , etc., welcomed by users with mixed success). Ten-Tec, unlike Watkins-Johnson, had no dealings with government agencies and the US military prior to the release of their RX-340 and RX-331 receiver models. Unfortunately, Ten-Tec found itself navigating bad waters and the old asset (including the old address was put up for sale several times, until the acquisition (around the year 2017) by Dishtronix, an Ohio-based firm whose President and CEO is Steven M. Dishop N8WFF. Unfortunately, despite the many promises of the new management regarding the continuation of the production of old and new models, the only fact is the sale of the old factory in Sevierville, TN and the acquisition of a two-room apartment in a shopping center in Dayton, Ohio. Uhmm… honi soit qui mal y pense!

[3]: The HF-1000/HF-1000A model was produced by Watkins-Johnson in a limited period of time around the turn of the century (between the years 1994 and 2000 approximately). Similar in appearance to the WJ-8711 and the WJ-8711A, the HF-1000, for reasons that are not well understood yet, it was missing of the 16 kHz selectivity position (the widest available was in fact 8 kHz) and had a slightly lower selling price than the other models. The HF-1000 and the WJ-8711 firmwares can be upgraded to the latest versions (V04.01.10 for U12 and V04.02.07 for U56) as specified in the text of the article anyway.

[4]: See:;wap2

[5]: See:

[6]: See: Paolo Viappiani, “The Watkins-Johnson receivers of the WJ-8716/8718 Series”, in: RadioKit Elettronica (an Italian magazine published by Edizioni C&C – via Naviglio, 37/2 48018 Faenza (RA), Italy), #12/2015, page 65.


[8]: All documents and manuals of the WJ-8711, WJ-8711A, HF-1000 and HF-1000A receivers can be found on the site: I recommend not to overlook the various versions of the manuals and options, as well as the interesting Data-Sheets. As for the Ten-Tec RX-340 and RX-331 receivers, the relative manuals and diagrams can be found at the addresses:,

I also recommend taking a look at the related Data-Sheets at the addresses:

[9]: See: on page 9.

[10]: See: and: Other interesting reviews can be found at: ed: Incidentally, additional Figure #26 (left) shows the early Samsung fluorescent display used on some early RX-340 and the green 7-segment LED display used in the WJ-8711 Series receivers (right)..

[11] From Head Italy of Rome – Viale dell’Arte, 85 – 00144 Rome, tel. +39 06.5744642 and +39 06.57284549, email: [email protected], The company, which replaces the former Watkins-Johnson Italiana, can provide assistance to all Watkins-Johnson receivers and generally has all the necessary spare parts. Unfortunately, Head Italia is used to dealing with government and military bodies, so their interventions are not too cheap… but desperately, it is better to try to ask, they are kind and helpful people.

[12]: Look at: and: The “.pdf” file must be RENAMED (not converted!) to a .zip extension, so it can be unzipped in order to obtain the firmware files (WJ_8711A_U12_04_01_10.hex, 361 kB and WJ_8711A_U56_04_02_07.hex, 181 kB) that can be “flashed” quite easily into the EPROMs by using a cheap USB programmer as the one shown in Figure 27. Obviously the file is available to everyone absolutely free of charge.

Please notice that if you want to use already used  EPROMS you have to completely erase them via an U-V device before re-flashing.

[13]: Look at: (AllMetalParts.Co.UK, Unit 4B, Pond Farm New Years Green Lane UB96LX Harefield, Uxbridge, UK) – Phone: +44-01895633570 (between 9-4 Mon -Fri). They produce two case models, both suitable for the T-T RX-340A receiver:

1) 3rack unit 19” Flat top stackable bottom cabinet 300mm deep (AMP05002F);

2) 3rack unit 19” Stackable top and bottom cabinet 300mm deep (AMP05002).

You can contact them by writing to: [email protected] and/or to: [email protected].

As it seems that in this period there are some difficulties in contacting them via mail, I warmly suggest to try to call them instead.

Important Notices:

  1. a) – Many special thanks to my friends Mauro Trazzi IZ1GCX of Arizzano, to the Dipl.-Ing. Ralph Menn of Saarbruecken (Germany) and to the two quoted “anonimous” Italian volunteers: without their help and hard work I couldn’t have written this article.

A warm thank also to my Belgian friend Joseph Bozzer, who in the past years sold me his precious and rare WJ-8711A-3 S/N 37 complete with its original Hammond case and to my dearest friends Dr. Roberto Mazzitelli of Monteforte d’Alpone and Antonio Gema of Berzo Demo: both of them helped me so much  in finding a good Ten-Tec RX-340 at  a reasonable price and in purchasing it.

  1. b) – Despite the addition of many new figures to the article, I decided not to alter their original numbering order and just to add the new ones  here and there This was for more clarity and in order to prevent any possible confusion, of which I apologize eventually, Thanks again for your attention!
  1. c) – Any comments, critics or suggestions from readers are very welcome.
Spread the radio love

16 thoughts on “Comparing the Watkins-Johnson WJ-8711 & WJ-8712 with TEN-TEC RX-340 & RX-331 receivers

  1. william badura

    Hello Paolo … About 5 years ago i purchased a Watkins Johnson 8711a-3 Hf receiver on EBay from a gentleman from South Korea … The serial number is number 1 …. I would like to learn more about this unit …. Any corispondance would be appreciated …

  2. Bob Watson

    Congratulations on such an extensive and well researched article.

    Over the years, there has been a lot of misinformation on the receiver origins. I think I have better insight into this topic because I was one of the design engineers for the WJ-8711. Rick Lober managed the latter part of the development and is generally correct in his statements.

    The development of the two radios was initiated by a government called, bidders conference that I attended. The subject of the conference was announced just before. The government said that they wanted a lower cost replacement for the WJ-8718 with an upper limit of $4k per radio. (They were paying more than twice that for 8718s in quantity.) There were four potential suppliers present, but only WJ and TEN-TEC took on the challenge of producing 6 prototypes at $4k each. All development costs were borne by each company. The requirements were heavily influenced by the WJ-8718 which the government had purchased in relatively large quantities ( I think several thousand). The WJ and TEN-TEC have very similar front panels because the display and tuning knob size were part of the government specification.

    It needs to be made perfectly clear that there was no contact of any kind between the two companies regarding this design. The technical successes or failures of the two designs were fully controlled by their independent engineering teams. A quick look at the excellent pictures provided in your article clearly show major differences in the design approach. For example, WJ used surface mount assembly and only a few wires and compartments. The performance specifications also have significant differences. For example, with the preamp off, the WJ maximum noise figure is 14 dB, and the TEN-TEC max. is 19 dB.
    The use of a triple conversion scheme is just the most obvious approach to solving the receiver problem. The use of 455 kHz for an IF was common as early as the 1930’s and was supported by standard parts.

    The decision to design the radio using a DSP back end was fairly easy, because we were already producing an SSB tuner that covered most of the HF range. Steve Hedges had managed that development team. He, I, and other members of that team pushed to use the same techniques for the 8711. It was just the logical thing to do. The days of crystal filters were effectively over. I am sure that TEN-TEC was independently making the same decision to move to DSP.

    The department manager that supported the 8711 development before it was transferred to Rick Lober’s group as Acie Vickers, who eventually went on to be President & CEO at Herrick Technology Labs.

    The WJ preselector was an option because it provided little improvement in radio performance. This is because the 8711 first mixer is very robust. The typical second order intercept point is greater than +60 dBm, which for the time was a good number.

    The MTBF specification, I believe was part of the original solicitation, but even if it was added later, it was NOT a request from WJ. Given that these radios were expected to run 24/7, the 10,000 hours represents about three years so the MTBF requirement is reasonable. I think that the TEN-TEC radio was probably capable of meeting this specification (although there may have been a temperature issue) so this is unlikely to be the reason they did not sell more radios to the government. It is my impression that they did in fact sell significant numbers of radios, but I am unsure.

    WJ sold over 10,000 8711s in various physical configurations. The quantity selling price was about $3200.

    I am still designing radios for DRS, the company that ultimately purchased the WJ division that made the 8711. The current best-in-class HF radio is the SI-8746 “Harrier”. It directly digitizes the entire HF spectrum with exceptionally high second and third order intercept points, an overload level of +5dBm without attenuation, internal spurious less than -130 dBm, and crystal-oscillator-like phase noise. It outperforms all of the classic superhet HF radios by a large margin. It does cost a bit more…..


    1. Bob Watson

      In a followup to my earlier letter, I wish to emphasize how the designs of the two radios were done totally independently. The externals and specifications were driven by the government requirements.
      The excellent photos in your article clearly show a very different internal construction between the two radios.
      The schematics for the 8711 found Here:
      and for the RX-340 found here: and here: , clearly show how very different these designs are.
      The choice of first and final IFs are different, as are designs of the mixers , amplifiers, synthesizers, A/D converters and DSP processors.

      The similarities between these two radios is simply attributable to “form follows function”.

      It is unfortunate than Ten-Tec is no more. They were a major resource for the serious radio amateur.


  3. Bob Colegrove

    I worked for W-J from 1967 until 1969. Some history has been compiled at As I was told, the receiver end of the business began in someone’s garage in Bethesda, MD under the name of Communications Electronics Inc. (CEI). When I got there, fresh out of the USAF, they were in a fancy new building in Rockville, and were soon bought out by W-J sometime in ’68 or ‘69. My staple in trade was mechanical assembly of the front panels and mounting them to the chassis. For multi-band receivers, there was no such thing as a band switch. Instead, complete and separate tuners tailored to the specific band formed the front end. Everything was handmade in house. The big product at the time was the 4-band RS-111-1B Series (30 to 1000 MHz), one of which went on to Watergate fame. My heart’s desire would have been a CRT signal monitor, which dynamically displayed a large band of frequencies as you tuned the receiver – sort of an SDR waterfall of its day. I am still looking for a DRO-50 Nixie tube frequency display designed specifically for the Hammarlund SP-600.

  4. Adam Ellis

    Thankyou Paolo, for your very comprehensive article on these receivers and for taking the time to illustrate it so well.

    I have been fortunate enough to find an RX-340 at a very good price and it has become the most used and prized receiver in my collection.
    It is an older version with the A revision firmware, but it performs flawlessly with very nice audio connected to a Sangean DAR-101 mp3 recorder for logging via the headphone output.
    My unit also exhibits the BITE failure you outlined regarding the missing wire, so when I pull it out of the rack, it will get a once over with the covers off. The volume pot is also noisy on mine too.

    You have provided some very useful and interesting information on both receivers that will help keep many examples going into the future.

    73’s and thank you again!

  5. Sealord

    I’ve had good results with Attack 0.80, Hang 0.01 & Delay 25.0 (almost the same as the Slow), but depending on conditions & signal strength you’ll need to tweak accordingly. I find the slower the AGC is, the better the sync works for the most part – starting with the Hang setting.

  6. Art Delibert

    Sealord — What settings do you use in the programmable AGC to get the best behavior from the SAM function? Thanks in advance.

  7. Sealord

    Thanks so much for this article! I have always wondered what the behind-the-scenes scoop was on these two receivers. I have an early RX-340 SN10063 that I’ve owned since 2000 and still use it on a daily basis. One thing I’ve noticed in most reviews is the audio quality from the DC coupled tap on the TT not being mentioned. Since it is designed for digital modes and is capable of producing the full audio frequency bandwidth, it also provides some of the best sideband audio as well and really let’s you here how nice the SAM is. If you use the programmable AGC, you can get the sync detector to work nicely without it loosing lock as much (that’s the trick).

    A few other things – at one point Ten Tec issued the owners a small AL shield that you installed due to it hearing one of it’s mixer’s(?) free of charge. I still have the paperwork/instructions they sent for this…but I never noticed any issue regardless before & after install. Also, my receiver came with the earlier software, before sending me the 1.10A version I am currently using. I still have the first eproms along with the removal tool they sent. The fluorescent screen on mine has no issues whatsoever and adjust the brightness level all the time depending on environment. I do get a failure on the 1st mixer often but if I perform the adjustment procedure on the board, it will pass.

    As far as parts go, there was an individual on ebay (potamacstore) who was selling new circuit boards for the RX-340/331 (81772, 81790, 81727, 81823 & 81817) in 2022.

    1. Sealord

      Forgot to add I also had issues with the power supply after some time due to the cold solder connections mentioned in this article, but after touching them up with a soldering iron have had no issue since.

      For those interested in adjusting the DC mixer I mentioned earlier, Ten Tec sent me this back in 2007:
      Set the radio at 0.00Mhz and in LSB mode.
      Using the front panel S-meter, gently (it’s very sensitive) adjust the trimmer cap (C11) for minimum S-meter reading.
      Shoot for S-9, but the BITE test should pass if you are at S-9 +10db or lower…

      Here’s a link to the I.F. shielding instructions for the part they sent out in 2002:

  8. Eric Richards

    Excellent article! My ‘340 has behaved itself over the years, so that sleeping dog can lie. It’s unfortunate that T-T is largely a name only instead of a fully operating company. I bought from them after the factory allowed me to audition the radio onsite, knowing full-well I couldn’t purchase one that day, and an engineer answered my questions about the preselector and how it would behave.

    They were an amazing company to work with. It’s a shame that they didn’t survive.

    I bet that the glue they chose for the EEPROMs are dissolveable by an agent that won’t damage the rest of the PC board. What it is is a long lost secret.

  9. Art Delibert

    Many thanks for an excellent article. I have often wondered whether the reported cooperation between Watkins-Johnson and Ten-Tec in devising the specs for these receivers is denied or hushed up because of concerns that it possibly violated American anti-trust laws. In fact, for that reason, it may not have been widely known even within the companies, but kept to a very limited group of employees who had a need to know.

    I don’t have a WJ receiver, but I have used a Ten-Tec RX340 as my main receiver for several years and I’m very pleased with it. I have noted only two real problems: (1) The receiver seems to lose sensitivity within about 10kHz of very strong signals; that is, the close-in dynamic range is poor. (2) Several times over the years the tuning display goes bad; the radio still tunes, but the displayed frequency doesn’t change. At the left of the display, where it normally shows the mode (USB, LSB, etc.) it says “BSB.” I have always been able to remedy this by opening the receiver and removing and reinserting all the cable connectors.

  10. Lee Reynolds KD1SQ

    A very, very nice article. Grazie Paolo!

    Until the consumer level SDRs really took off something like there (or the Racal line) would have been something I should have greatly lusted for.

    Now, I look at these, admire them, but keep in mind I can get 95% of the performance for 10% of the price and in a form that can be easily repaired or replaced at no great cost if I use a modern SDR.

    These earlier receivers are wonderful devices, imposing and (usually) extremely well engineered but as time passes the purchase and use of these becomes more and more akin to the antique car collecting fetish (as more a question of aesthetic appreciation than easily continuable functionality) or, indeed, any collecting of beautiful or interesting old items.

    Myself, I’d just like to some day pick up an old Marconi CR-100 and fix that up. At least the microprocessor would be easy to replace…

  11. John

    What a great article, thank you!

    Those solder joints on the TenTec don’t look cold so much as mechanically fractured, but either is possible. Those white Insulation Displacement connectors used for board to board connections have given me problems with my TenTec Centurion amp, which otherwise is a great piece of gear.

  12. Dan Say

    Woof ! A 42 page PDF when printed to Adobe Acrobat.
    Very nice, very interesting, but outside my price range in those recent days.

    And sadly, many bands of broadcast radio are silent now.

  13. Julian Stargardt

    Thank you Paolo
    Wonderful, helpful, well documented and useful article!
    If you have any updates, let us know!

    Tanti Auguri,


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