An Interview with Ramon Vargas Patron
IntroductionIf you've been a regular visitor to Circuit Exchange, you will have seen many articles and circuits by Ramon Vargas, over the last 16 years! I thought that it was appropriate to write an article about Ramon, his life and career in Radio and Electronics. I'm sure sure many viewers will find this interesting. Ramon lives in Lima, Peru, with his wife, and his primary language is Spanish, although, his English and grammar are perfect.
Included in this introduction are some of Ramon's early encounters in the wonderful world of electricity and electronics. Ramon has produced university lectures that followed thereon, helping the experimenter or researcher when field tests of newly built electronic systems disobeyed theoretical calculations, or when the theory had gaps that could be the culprit of prototype failure. Ramon wishes to state his enthusiasm and permanent interest in sharing with engineers, students and radio-experimenters the results of his own investigations, following the lines of personal thoughts that declare that scientific and technological discoveries are property of humanity and access to them is inalienable.
Work at Inictel-Uni, Peru.
The impressive looking building on the left is INICTEL-UNI in Peru, situated in the capital city, Lima.
INICTEL-UNI is not a university, it is the National Institute for Research and Training in Telecommmunications, and it was merged into the National University of Engineering - UNI of Lima back in 2006.
Courses offered include Cisco certifications (the Institute has a Cisco authorization), embedded circuit/systems, Optical Fiber systems deployment and measurements, data network connectivity and Microsoft Office.
Early Radio and Electronic Work
Ramon Writes:Television knocked our door at home in 1959. Live programs, TV series of all classes, among which were the science-fiction types. Given the special predilection of this servant for science, especially anything related to radio waves and light phenomena, he was given on his 11th birthday a kit carrying parts and components for experiments in electronics, manufactured by the Philips Company. Wonderful little three-leg devices known as transistors could amplify the weak currents from a microphone until they could be heard on a loudspeaker. And everything with a 9-Volt battery! Fantastic! But, how did all that operate? Who could explain it to the young experimenter? More yet, the instructions manual was written in English. The author was lucky enough to have learned that language since a little child, so at least something from the manual could be understood. Months passed and the small 6V/50mA bulb from the kit kept intriguing the future electronics engineer. Why does it glow when subjected to 6 Volts? Why will it go off suddenly? Go figure. Dad was a public accountant and his knowledge on electricity permitted him to perform some minor repair tasks at home. Unfortunately, he couldn’t answer the disturbing questions. Twelve months had to elapse before someone would give the diligent student a small book on radio experiments. Coils, variable condensers, more transistors and a new electronic component: the audio transformer. It’s like a 220VAC to 6VAC transformer for the doorbell? “No, it’s not”, we were told in a Philips electronics store in Lima downtown, “it has a different frequency range”. That was another question to be answered years later.
The laboratories on electronics from the Physics course at school were useful for understanding something about electronic currents and their real and conventional senses, vacuum tubes versus transistors, electrochemical batteries. Wonders! We could not end our studies in high school without constructing our Carbon-Zinc cell with electrolyte and depolarizer, just for lighting up a small 1.5-Volt bulb! Potassium Permanganate really worked helping our cell do its job.
In fifth grade we were already playing with more serious apparatuses. We would transmit speech using shortwave radio! Yes, the one able to travel from one continent to another, reflecting in the upper layers of the atmosphere, known as ionosphere. Of course, the listening range was indoors, but there we were. Some day we would understand why that small gadget known as shortwave radio transmitter could be heard here and there, without wires attaching it to a fixed point. Radio waves ought to be something very complex. Once started university studies, we could expect to learn.
A lot of experimentation was done at home. We burned the fuses of the first floor.☺️ Various small transmitters were tested, intercoms, automatic lighting and others. But we could not understand why 100uF here and 0.022uF there. A 100k-ohm resistor in this point of the circuit and 3.3k ohms to the emitter of the transistor. But why? The mystery would be revealed some day.
Ramon applied to the National University of Engineering, studied and attended the ten semesters of rigor. The reason for the existence of each electronic component was finally understood. However, employment for graduates of the electronics career demanded prospective employees knowing how to apply the theory of electronic circuit analysis to the circuit design field. We didn’t study the career to work as a salesman for electronic appliances. We wanted to design measurement equipment, 50...100...300-Watt audio amplifiers, medium wave and shortwave AM radio transmitters, narrow-band and wide-band FM transmitters, VHF equipment....Where do we get all the knowledge for this? We must learn in the job, with our work. Upgrade existent equipment. Design measurement instrumentation, starting from the most simple.
Work at InictelI asked Ramon about his work career, and he replies:
I was lucky to start working in 1979 for the National Institute for Research and Training in Telecommunications – INICTEL. One year spent in the Research Department and then in the Instrumentation Division of the Central Laboratory Department. Our responsibility was to perform preventive and corrective maintenance to instruments and general purpose equipment, such as DC power supplies. A great number of these were constructed by engineers under our supervision, with designs based on original work of the author. New designs were studied and tested for power supplies carrying protection against overloads at the DC output and transients at the AC input. A good deal of the design methods was kept as handwritten material and some was sadly lost, so that when we turn to instrumentation design, we start keeping typewritten records, and with the coming of digital computers, records are saved as digital data, making more easy the documentation of circuit changes and updates.
The well-equipped laboratories of INICTEL permitted special tests to be conducted in order to obtain data not commonly found in compact datasheets of some electronic components. University text books treated the operational amplifier (OP-AMP), in simplified terms, as a device having a very high differential input impedance and a very high differential voltage gain, which could be considered as infinite. The low-frequency pole of the compensated OP-AMP was generally omitted in the calculation of linear applications. When linear- oscillator design is attempted at our laboratories at frequencies above 100kHz, we find that conventional OP-AMP design formulas led to unexpected large errors when real- world and theoretical results were compared. The author decides to study the effect of the low-frequency pole in the oscillator calculation and arrives to a more accurate formula for the oscillation frequency. This study was reported in a technical article.
The variable-frequency Wien-bridge oscillator is popularly implemented using OP-AMPs. It features the design limitation mentioned in the above paragraph. It commonly uses a two-gang precision variable capacitor with identical sections, a high-priced component. The author conceived a design that required a single-section variable capacitor, which contributed to minimize construction costs of audio generators for training purposes in the Institute. The idea shed light on two articles related to the new type of oscillator.
Wave generation and shaping is a topic of study in the field of non-linear electronics. Triangular to sine-wave conversion is very interesting because it uses piecewise-linear approximation techniques, along with Fourier-series calculus and high-speed silicon or Schottky diodes for introduction of controlled non-linear distortion. Lacking at the time enough detailed technical information on the shaping process for the said wave types, we decided to focus on a deep study of the process, developing formulas for the design of the shaping circuit.
The audio transformer, considered by some as outdated and blamed to be a harmonic- distortion generator, is considered by others as an elegant device in audio systems that permits impedance matching between stages and the delivery of power to a load with galvanic isolation. The point here is that the high-quality audio transformer requires of a design that has been maintained as a specialty by some manufacturers. Not every audio transformer is of a high-quality type. It’s a circuit component that requires a knowledgeable user in order to be adequately selected for technical specifications and brand. Two articles were written on the interpretation of the technical specifications of an audio transformer. They clear up, hopefully, fundamental aspects that are usually so confusing. One of them is the use of audio autotransformers.
Tone control networks in audio amplifiers permit the independent adjustment of bass and treble frequencies. In the public domain formulas exist for the design of passive or active tone control networks, but the mathematical proofs for them rarely exist on Internet archives, books or paper magazines. We have developed the study of passive and active tone control networks and published a step-by-step derivation of pertinent formulas.
Radio experimenters worldwide usually employ receivers of the regenerative type when listening to medium and short wave bands. It’s a receiver very easy to construct and of simple design. Currently, versions using vacuum tubes (very popular in the USA and Europe), bipolar junction transistors (BJTs) and junction field-effect transistors (JFETs) are commonly found. All of them are based in a single principle: an oscillator in the verge of oscillation is potentially a high-gain amplifier. This effect can be used in the construction of high-gain small-signal amplifiers. We have written several articles regarding the utilization of regenerative amplification. In this context, this type of amplification also makes use of negative resistance, which can be synthesized employing two active devices. We wrote an article on this topic with information that has been very little disseminated by other authors previously.
A report has been written related to the use of negative resistance generated by an independent circuital block and coupled to a sine-wave oscillator with high harmonic content. This is done with the objective of lowering harmonic distortion and obtaining a very high-quality sine wave. It’s a topic rarely touched by authors as such, but related to “Q multipliers”.
AM radio receivers operating off the energy of the passing radio waves captured by the antenna is a topic that causes fascination to hobbyists and radio experimenters. With a little of accurate technical information it is possible to construct simple receivers for learning purposes or fun, even using recycled parts from old vacuum-tube receivers and transmitters. The author has published various articles in this aspect as technical reports of tests conducted by him.
The demodulation of amplitude-modulated signals with carrier (DSBC) and single side band signals (SSB) is studied using trigonometric formulas, applying them to product and regenerative receivers. It’s a very compact and useful article. All the necessary information in one place.
Radio-frequency applications several times make use of the capacitive transformer to step-up or step-down impedance levels. Again, the corresponding formulas appear to have not been published conveniently by authors, nor their mathematical derivation can be easily found. This author made a complete study of the capacitive transformer for applications as an impedance transformer and its utilization, as such, in a low-frequency oscillator.
The convenience of having in a single place all commonly known RC phase-shift oscillator configurations, with the derivation of corresponding formulas for the frequency and the condition for oscillation, which permit computation of component values, not only for BJTs, but also for JFETs and vacuum tubes, motivated the author to write a comprehensive article on this matter, which also treats the special case of the use of five RC cells for phase shifting. This information can ́t be found in available technical literature with the depth of analysis and complexity that the article offers.
The general theory of the State Variable Filter is proposed and discussed, working out block diagrams and schematics for phase-compensation, pass-band and band-rejection configurations. The topic of Switched-Element Filters is also treated. These are excerpts of the thesis of the author for his professional degree in electronics.
Finally, we wish to mention that it would be of great satisfaction for the author if a young reader awakens his interest for self-guided research after reviewing this humble work, result of 37 years of dedication to applied electronics in our Institution.
EpilogueThis concludes the fascinating story of Ramon's work and career of 37 years of research at Inictel. I hope you have enjoyed reading it as much as I have. Some of Ramon's circuit and articles appear on this site and can be found in Radio Circuits Index and on the Analysis, Design and theory pages. I am especially grateful to Ramon for all his contributions over the years, and I sincerely hope to continue my association with him.
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