Tesla Receivers

Tesla receiversAuthor: Vladimir Polyak, RA3AAE

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Paper delivered at a rally 30/7/06 "Ugra-2006" club "RU-QRP"Dear colleagues, friends and foreign guests! Most recently, on July 10, we celebrated the 150thanniversary of the birth of a brilliant scientist, inventor and engineer Nikola Tesla. Well known for hisachievements in the field of electrical engineering: generators and AC motors, transformers andhigh-voltage power lines. They are now based all power.For several reasons, less known for his work in the field of high-frequency currents - the foundation ofradio engineering, and after Tesla demonstrated wireless transmission of signals for several years beforethe Lodge, Popov, Marconi and other researchers. His patents cover Marconi patents that the U.S.Supreme Court has recognized, but too late, in 1943,I myself turned to the study of Tesla's work after a series of experiments with a crystal set, held just forfun. It turned out that under Moscow possible speakerphone taking multiple radios. For maximum powertransfer from the antenna to the detector, I found out that we must abandon the tuning capacitor in theantenna circuit and adjust the inductance until the capacity of the antenna resonance at the frequencybeing received. The scheme coincided with the scheme Tesla (Fig. 1)!

In a wireless transmission Tesla used four (!) Resonant circuit tuned to the same frequency - two fortransmitting and two for receiving side. The first circuit formed by closing spark gap S capacitor andinductance of the primary winding L1 (Fig. 1a). To get more power to the ultralong waves Teslarecommended using HF alternator (Fig. 1, b). The second loop is formed by the secondary inductance L2and capacitance antenna. A large number of secondary turns and configure it to allow resonance to obtainhuge antenna voltage characteristic when operating at long wavelengths with electrically small antennas.On the receiving side to use the same resonant transformer circuits L3S ANT and L4S. The letter R denotesa recording device, which in those years, in fact, called the receiver. To all of the receiver, the name was

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attributed much later. Registrars could serve coherer, electromagnetic relays, galvanometer, gas dischargetube and other instruments.Tesla perfected and widely used in the years coherer - a tube with the findings filled with metal filings. Inthe normal state due to a thin oxide layer on the filings coherer resistance is large, but under theinfluence of high-frequency oscillations occur microdischarges in the thick sawdust conducting chains areformed and the resistance of the coherer sharply. To return to the original state coherer must shake, orconducting state persist after the signal. O. Lodge proposed for this purpose movement with a hammer,Popov - relay with a hammer at anchor, triggered by the signal, and Tesla has solved the problem of moreoriginal, offering a rotating coherer! Sprinkles sawdust immediately destroy conducting chains, as soon asthe signal stopped.But it's not all his improvement coherer receiver. He first pointed out the need to adjust the antennacircuit in response to the signal frequency. This setup not only allows you to adjust the antenna to theinput of the receiver, but also radically improves small receiving antenna, allowing it to extract from theincoming wave significantly (Q times, Q - Q) more power. To set up the antenna circuit with a cohererinclude additional adjustable inductor L1 (Fig. 2). With a decrease in the resistance of the coherer fromexposure to RF fluctuations in current from the battery passes through the throttle RFC, coherer A coil L1and worked on relay R.

Tesla went a step further in improving the coherer receiver. He fitted the low-power integrated heterodynereceiver! In those years there were few devices to generate RF oscillations, so LO was like a sparkgenerator, but instead was used arrester mechanical chopper D (Fig. 3). By oscillator circuits includebattery B2, rheostat r, ensures the optimum level of the LO signal, the capacitor and the primary coil ofthe transformer L1. With the closure of the switch D-charged battery capacitor is discharged to the coil,creating a series of damped oscillations with a frequency approximately equal to the frequency of thereceived signal.Corum brothers, researchers of Tesla believe that RF voltage that is generated in the secondary coil L2,and applied to a coherer, brings it to the point of breakdown and constantly kept alive. In this telegraphsignals can be received on the beats that radically distinguishes the Tesla mode on the mode of thecoherer "envelope detection" used Branly (the inventor of the coherer), Lodge, Popov and Marconi. Corummodeled this receiver Tesla and experimentally established [1], the sensitivity of his when the localoscillator and the same of the coherer increased by 66 dB (with tens of millivolts to tens of microvolts)!But not only is the reason why a good job and a high sensitivity receiver Tesla (in Colorado, he recordedthe lightning at a distance of many hundreds of miles). Another reason - the most in improving thereceiving antenna. On the super-long waves any real aerial - an electrical short, its length is much smallerthan l / 4. A recent study [2 - 5], to increase the power, selects the antenna coming out of the field, can



be through the intensification of its own near-field, increasing its volume. It is the near field, interactingwith the incoming wave, causes the flow of energy sent to the receiving antenna wire. I was able to showthis by means of elementary mathematics in a number of articles, unfortunately, are not translated intoEnglish [6 - 8].Strengthen the self-field of small receiving antenna and bring it to the normal size of the field, a largeantenna in several ways:1. Adjust the antenna to resonance and to maximize the quality factor of the antenna circuit. It can beshown [6] that the quality should increase inversely proportional to the cube of the linear dimensions ofthe antenna.2. Bring a dish vibrations own oscillator synchronized in frequency and in-phase with the incoming signal.3. Add to antenna adopted and amplified vibrations, ie to use positive feedback, or regeneration.As we have seen, the first two methods Tesla applied in practice. Whether he used the regeneration? Theanswer is simple - yes. In his diary ("Colorado Springs Notes") remained coherer circuit regenerativereceiver (Fig. 4). It, however, does not show space antenna and ground (for Tesla it was obvious, and wecan only guess), but it is very clear principle of the device in which the coherer replace conventional sparkgap generator at the time.

While there is no signal, the resistance of the coherer A large capacitor charged to the battery voltage andfluctuations in the primary and secondary circuits of the transformer, a coil L1 and L2 are missing. When asignal is reduced resistance of the coherer, discharge the capacitor to the coil L1 gives oscillations with afrequency signal (remember that the circuit tuned to resonance!). Their amplitude in the secondary circuita lot more (as more number of coils L2, and it is tuned to the same frequency.) This amplified voltageagain affects coherer and even more to lower his resistance. There is a positive feedback! Apparently,Tesla regenerator could be raised up to the self-excitation (to make feedback more critical), adjusting thevoltage of the battery and the resistance of the rheostat to r. Initial impetus to the excitation ofoscillations could give sprinkles sawdust in a rotating coherer, randomly changing its resistance.Be that as it may, there is no doubt now that the regenerator invented at least 15 years earlier than didEdwin Armstrong (1914) and Lee de Forest (1916). It was easier - de Forest has already proposed by thetime three-electrode radio tube (triode), and it is widely used as an RF amplifier oscillation.It remains to consider one more brilliant in the simplicity, elegance and perfection synchronousheterodyne receiver N. Tesla. [9] The patent application was filed in June 1899 in the receiver is usedelectromechanical transducer frequency (Fig. 5a), who appeared, in fact, the world's first double balancedmixer. On a rotating drum were conducting strips, in one connected to the top and bottom brushes,connected, in turn, to the antenna and ground. The other two brushes sliding on the strips, was attachedstorage capacitor C.



When the drum rotates capacitor plates alternately concentrating it to the antenna, then to ground. If theswitching frequency coincides with the frequency of the signal, the capacitor accumulated synchronouslyrectified voltage. The switching frequency is equal to the product of the drum speed (number ofrevolutions per second) by the number of pairs of strips could be tens or even hundreds of kilohertz.Accumulated tension was proportional to the amplitude of the signal and the cosine of its phase relative tothe phase switching. In modern notation, the receiver circuit is shown in Fig. 5b.The text of his patents describes two features of the receiver, is radically different from all other radios ofthe time. First, it is more sensitive. The capacitor stores charge for periods of a weak signal. As a result,the voltage across it is set close to EMF signals in the antenna. Discharge produced by a recording deviceR, such as telephones, are also periodically, with the second drum, switching phone chain with AF. Movingthe brush on the second drum up and down, you can adjust the duty cycle of the sound pulses, ie, thetime constant of the discharge circuit. Practice shows [10], the sensitivity of a good phone can be betterthan 10 mV, and in times of Tesla could already do a good phone! Consequently, the same order wasobtained and the sensitivity of the receiver. Agree that this figure is amazing!Another feature of the receiver - its great selectivity. If the frequency of the signal does not coincide withthe switching frequency of the first reel (not equal to the frequency of the local oscillator, in modernterms), the capacitor is simply not accumulate charge, since it will come bipolar pulses. Increasing thecapacity of the condenser, it is possible to narrow the bandwidth of at least up to a few hertz! In essence,the receiver - simultaneous narrowband filter tuned to the frequency of the signal. It does not detect assuch, but only the conversion of the signal frequency zero, that is, to direct current. The same thing we doin the modern direct-conversion receiver, getting great results. The closest thing to a modern schemeTesla fazofiltrovomu receiver, as his prototype.From "time immemorial" Tesla gives us another tip - set the synchronous filter at the receiver input. As faras I know, this decision has not yet been used in electronics, but promises great benefits, promising togreatly increase the actual selectivity of any modern radio.Literature1. KL Corum and JF Corum. Tesla `s Colorado sprigs Receivers. http://teslasociety.com/teslarec.pdf2. B. Beaty. Energy-sucking Radio Antennas, N. Tesla `s Power Receiver. http://www.amasci.com/tesla/tesceive.html3. B. Beaty. More musing On Energy-sucking Radio Antennas. http://www.amasci.com/tesla/tescv2.html4. JF Sutton and GC Spaniol. "Black Hole" Antenna. http://www.unusualresearch.com/Sutton/sutton.htm5. US Patent # 5,296,866 "Active Antenna". NASA GSC-13449.6. Polyakov. The receiving antenna - a "black hole"? http://www.qrp.ru/bh.zip7. Polyakov. On the near field of the receiving antenna. CQ-QRP, # 8, Oct. 2005, p. 10 - 18. Circuitry 2006,



3, p. 35-37 and number 4, p. 38-40.8. Polyakov. The secret is simple regenerator 20s. CQ-QRP, # 11, April, 2006, p. 32 - 35. Circuitry 2006, 7, p. 14, 15.9. US Patent # 685,955. N. Tesla. "Apparatus for utilizing effects transmitted from a distance to a receivingdevice through natural media". Patented Nov. 5, 1901.10. Polyakov. What is the sensitivity of your phones? CQ-QRP, # 10, Feb. 2006, p. 16 - 19.August 23, 2006, Vladimir Polyak, RA3AAE

Viewed: 39387 time (s) Updated 13/09/2006 at 22:51The author - Vladimir Polyak, RA3AAE

Discussion on this article09/16/2012 20:57 Unlock pliz ... - ua3xgm09.03.2012 10:37 Comments slightly different radio topic: * Part 1: in his time at ... - Aidar13/11/2010 17:36 A Th Popov? ... who was the FIRST? ... - Adik10.05.2006 11:45 "Registrar may serve coherer, electromagnetic relays, gal ... - Nicholas25/9/2006 9:50 Thank you for your feedback. Alexander: the FT-1000MP no input sync ... - Vladimir, RA3AA ...09/22/2006 5:44 Always check my materalov with interest, concern brilliant academic ... - RA0JV17/09/2006 9:16 Just amazes genius Nikola Tesla! Brilliant series ... - Yuri UR5VEB ...14/09/2006 16:47 Vobscheto synchronous pass filter incorporated in ft 1000mp -1 ... - Alexander14/9/2006 9:39 Thank you, Vladimir! As always, a brilliant exposition of the most interesting and ... - Alexander RZ6FE ...

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Tesla Receivers