Interview with John Woodgate

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John Woodgate

John Woodgate - Principal Consultant, J M Woodgate and Associates

How did you get into electronics/ engineering and when did you start?

Like most circuit designers, at the age of about seven, with second-hand batteries and low-voltage lamps. Progressed to crystal radios and then tube radios. Those who only start at age 18 or even 21 should realise how far behind the field they are! Of course, the early years are characterized by error, but it is from error one learns. Things that go as predicted do not teach, only confirm.

What are your favorite hardware tools that you use?

The Lindos LA100 audio test set. Although it’s now old, it does almost everything I want. The Agilent DSO 3102A digital storage scope, which does many of the things the Lindos doesn’t do. Agilent 8591E spectrum analyser and HP 8640B signal generator for the EMC work. I can borrow a CISPR receiver if I need it.

What are your favorite software tools that you use?

LTspice, a free, very flexible simulation tool. Mathcad math application. MiscEl (freeware) for those odd calculations that tend to go wrong if done manually.

What is the hardest/trickiest bug you have ever fixed?

Most of the hard and tricky ones are due to not seeing the obvious, or a concealed fault, such as an open-circuit resistor that looks perfect. I’ve puzzled over that one at least three times.

What is on your bookshelf?

About 1000 books: I’m a compulsive reader. Apart from audio, RF and acoustics textbooks, there are historical novels and SF as well as some more ‘literary’ works. And hundreds of hard-copy IEC and BSI standards.

Do you have any tricks up your sleeve?

I have found that it is possible to use Mathcad to analyse circuit and system behaviours that seem counter-intuitive or in need of explanation for other reasons. It can take some time to develop the necessary algorithms, but it’s usually worth it. For example, why does a sound system in a stadium draw far less power from its supply when in use than it does when conventional testing is in process. A superficial explanation is easy, but explaining the actual numbers is much more subtle.

I use similar mathematical techniques to determine from first principles the magnetic field patterns of magnetic antennas used for assisted hearing systems (audio-frequency induction-loop systems AFILS).

What has been your favorite project?

A TTL-based lottery machine, that earned much moola for my then employer’s company social club.

This was around 1965, when the law first allowed private electronic lotteries to be set up by social clubs.

Three 7413 Schmitt inverter oscillators drove 74141 decade neon tube drivers via 7490 serial-to-BCD counters so as to generate 2000 numbers (0000 to 1999), displayed as three rings of miniature neon tubes arranged in circles about 18 inches in diameter in a three-section display console (like three TVs side-by-side). Two had numbers 0 to 9, while the third had 0 and 1 alternately.

The random element was provided by the operators, volunteers from the diners in the company cafeteria. The counters could be stopped by operating full-size toggle-switches (the type used on household appliances), of a quick-acting type chosen for requiring a substantial force to operate. So it was sufficiently nearly impossible to tell the exact instant at which the switch would toggle and stop the ring.

I tested the randomness with my engineering colleagues as operators, and, of course, one managed to select 7,7,7,7,7,7,7, 2, 0, 9, 3, 6, 1 ….,. Considering the large number of remarkable things that could have happened, the probability of some one of them happening was about evens.

Similar apparently unlikely events happened twice more – the second draw turned up 0000, and at about the fifth draw, someone selected their own number. Both are low-probability events, but no SO low as to be very remarkable. I did check the randomness after a year and indeed every digit of each ring was represented within a range of only 5 occurrences.

However, we never found out why the head of the motor pool won a prize much more often than anyone else, and his name wasn’t Ernest G. Bilko. (;-)

A servomotor drive that helped to earn a fellow-student a First.

My fellow-student was offered a servo drive amplifier that had been made by a previous student. There were basically two problems with it – it could deliver far more current (from two 807 tubes) than needed by the servomotor that my colleague was using, and its stability was very suspect. Naturally, the performance of the servo system was unpredictable and sometimes violent.

So (overnight) I made a much simpler driver (based on just a 6SN7GT tube with a few resistors) with five times less current capacity and unconditional stability. This enabled the project (of which the servo was only a small but vital part) to proceed to success.

Do you have any note-worthy engineering experiences?

Saving a company (part of IT&T) several thousand pounds for screened cabins when I was an intern between my first and second years at college. The problem was interference with alignment of AM radios due to magnetic field from fluorescent lighting. By turning the alignment benches through 90 degrees, the magnetic field from the lamps was directed along the null of the ferrite antennas.

What are you currently working on?

Four fields:

operational and test equipment for audio-frequency induction-loop systems for assisted hearing AFILS;
specialized power-line communication for control of theatrical equipment.
British and International standards for electrical safety, audio-visual systems and EMC;
technical writing.

Plus a new laboratory/office building.

Can you tell us about the standards work?

I was introduced to British Standards work at an unusually early age, 25, possibly because I won an argument with a noted BBC engineer at a conference. At first, I participated through the Technical Committee of a trade association, but it was not very long before I was asked to join quite a large number of industry and British Standards committees and then international ones, in the IEC (International Electrotechnical Commission). I also participate in Audio Engineering Society Standards and Technical committees.

Standards work requires both technical skills and skill with words, and the combination is relatively rare. I thought the largest number of committees of which I was an active member was 32, but I’ve just had a count-up and it’s 34 at present. I also hold what I think is a unique office in IEC, as General Maintenance Manager of IEC TC100.

What direction do you see your business heading in the next few years?

More of the same, probably.

What challenges do you foresee in our industry?

There is still a shortage of analog designers, and this has gone on so long that many of the really great analog designers are retired or even no longer with us (we lost two in quick succession very recently, Jim Williams and Bob Pease). So there is a shortage of top-rank teachers of analog design as well.

Many products directed to the consumer are so complicated (just because it can be done at near-zero cost) that for the majority of people they are becoming almost unworkable. They are also becoming so small as to be physically very unfriendly to operate. A backlash is not impossible.

We need to simplicate, and, now, add volume rather than lightness.

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