Oleg Vladimirovich Losev (Russian: Олег Владимирович Лосев) was none other then the first person to record his findings in regards to Light Emitting Diodes (LED).Though he only lived to be 39 years old (May 10, 1903 – January 22, 1942) he had an impressive resume. Unfortunately for him, for Russia, and for electronic advances the Russian government did not take him seriously.
While Oleg discovered that a carborundum (silicone/carbon compound) point-contact junction (cats whisker) diode used in crystal radios produced light when current was passed through it. Thus was the first LED. Oleg published his findings in a Russian Magazine in 1927 but the LED was not a practical electronic component until 1962.
Mr. Losev also conducted experiments with negative resistance in semiconductor junctions and built the first solid-state amplifiers, oscillators, and superheterodyne radio receivers 25 years before the transistor was invented.
Just think of how much further Amateur radio and all other radio services might be today if Oleg Losev had been taken seriously in his time. It just makes me wonder what our ham shacks would look like today.
In 1895 Alexander Stephanovich Popov built an improved version of a coherer-based radio receiver designed by Oliver Ledge. It proved to be a good lightning detector. Whether or not he used it in conjunction with a spark gap transmitter to publicly demonstrate the transmission of a radio signal between two buildings on March 24, 1896 (Marconi did a public demonstration in September 1896) seems to be questionable. To this day Russia says that Popov, a Russian, was the inventor of the radio. One thing that can not be argued is that Oleg Vladimirovich Losev, a Russian, was the inventor of the LED.
This is copied from Facebook:
John, W1AI
6AK7 pentode in metal envelope.
As we saw in earlier posts the diode vacuum tube (or valve) became a triode by inserting a grid, known as the control grid, which allowed it to amplify audio and RF signals. The triode had a problem of interelectrode capacitance which limited the frequency at which it would operate properly. By adding another grid the triode became a tetrode. The second grid, called screen grid, has a positive DC bias but an AC ground via a bypass capacitor.
The tetrode was an improvement over the triode but it had a problem with secondary emission.
When the electrons pass the positively biased screen grid they speed up then when they strike the plate (anode) they may dislodge another electron and send it into the space between the screen grid and the plate. They may be attracted to the screen grid and establish a current flow from the plate to the screen grid known as secondary emission.
Secondary emission can cause a condition known as negative resistance where an increase of plate voltage will result in a decrease plate current. Negative resistance may lead to unstable operations.
Bernhard D. H. Tellegen
In 1926 Bernhard D. H. Tellegen, a Dutch electrical engineer, inserted a third grid following the screen grid and operated it at ground potential or slightly negatively biased. This grid, called a suppresser grid, prevents the electrons that were creating the secondary emission to be attracted back to the screen grid. Thus the pentode, five electrode, tube was born.
Both the tetrode and pentode tubes have high power sensitivity when compared to the triode tubes with the same power output.
Another tube designed to reduce unwanted secondary
Beam Power Tube Illustrated
emission is the beam power tetrode. Instead of a suppressor grid it has beam-focusing plates that are run at ground potential or slightly negative
potential. They follow the screen grid and cause the electrons to flow in a narrow beam to the plate thus pushing any potential secondary emission electrons back to the plate. The beam power tubes are usually used as power amplifiers for RF and Audio. The 6146 was a very
6146
commonRF final amplifier beam power tubes used by ham radio operators in the 1950s.
Many of the linear amplifiers used by amateur radio operators still use vacuum tubes.
Lee DeForest added the grid to the diode in 1908 and at that time radio signals below 200 meters (today we would say above 1.5 MHz remember as frequency goes up wave length goes down) was considered very high frequencies. When Amateur Radio Operators licenses became required in 1912 it was believed useful radio communications could only be done on 3,000 to 300 meters (100 to 1,000 KHz) so the ham radio operators were restricted to 200 meters and above because they would only be able to communicate about 25 miles (40 KM) or less.
Amateur radio operators proved the value of those frequencies above 1.5 MHz and continued to press the limits higher with very impressive results. The triode tube was proving it self but as the frequencies continued to go up and the power demands on the triode vacuum tube increased new problems
Interelectrode Capacitance
developed. The capacitive reactance of the interelectrode capacitance decreased as the frequency increased so as more power and higher frequencies were being attempted the triode proved to be unstable or might even go into self oscillation at undesired frequencies; and with an amplifier any frequency of self oscillation is an undesired frequency.
A capacitor is any two conductors separated by an insulator so any time there is a potential difference between the plate and the grid, the plate and the cathode, or the grid and the cathode there is capacitance. The results of this interelectrode capacitance are known as the Miller Effect, named for John Miller who described the effect in triodes that limited their high-frequency usefulness in 1920. If you would like to learn more about the Miller Effect http://en.wikipedia.org/wiki/Miller_effect has an excellent article but it goes beyond the scope of this post.
One solution was to use negative feedback (a small portion of output from the tube fed back into the input 180 degrees out of phase) equal to the positive
Typical Triode amplifier using neutralization. PA Neut capacitor provides negative feedback but C120 must also be adjusted for the right balance matching the interelectrode capacitance.
feedback caused by the interelectrode capacitance. This process is called neutralization. While this worked it reduced the overall gain (amount of amplification) of the circuit and it can be a tricky adjustment.
Another way to reduce the effects of interelectrode capacitance was to use a grounded grid 
amplifier. As the name suggests the grid is at ground potential of incoming signal. The input is to the cathode and the output is off the plate. This amplifier has a low impedance input and a high impedance output. While the circuit is a good one and still used in ham radio linear amplifiers today it sacrifice gain.
Many efforts were tried with varying successes and failures. It was not until 1926 that Dr. Albert W. Hull and N. H. Williams were credited with inventing the tetrode (four electrodes) vacuum tube. There does seem to be some argument that Walter H Schottky invented the tetrode in 1919. It is true that Schottky did add a second grid to the triode but he had very limited success with it.
The vacuum tube then had a cathode, control grid, screen grid, and a plate. The control grid was closest to the cathode and did the amplifying. The screen grid was between the control grid and the plate; it had a positive DC bias, a zero ground potential at the frequencies being amplified, and acted as a shield between the plate and the grid to reduce the effect of the interelectrode capacitance.
The screen grid greatly improved the frequency response and the gain. Neutralization was still needed to maintain stability in some instantiates. While the tetrode was a great improvement it brought with it new problems.
Some of the triode tubes from 1918 to late 1950s
The last post was about the vacuum tube diode. I forgot to mention for you European and other readers when I speak of a vacuum tube it might be what you call a valve. The term valve is a very good one because it really is an electron valve. Diodes, as well as all vacuum tubes, are electron check valves. A check valve for liquid will allow the liquid to flow in one direction but blocks it from flowing back. That is the same thing a diode does with the electron flow in a conductor.
Adding a grid to a diode is like adding a gate with a stem and knob to the check valve. The gate will allow the operator increase or decrease the rate of flow. For many years effective state of the art amateur radio equipment was made possible by the grid or as we will see later multiple grids.
If you don’t know how a diode works then I might suggest you back up to the previous post and read it.
John Ambrose Fleming
John Ambrose Fleming, an English physicist, worked as an engineering consultant for several firms including Edison Telephone and the Marconi Company. In 1904 Fleming conducted some experiments using Edison effect bulbs he had imported from the USA. He found the bulbs could be used as rectifiers which he called “oscillation valves”. Because of their greater efficiency and the fact that a hot spot did not have to be found the vacuum tube diodes detector soon started replacing the crystal detectors in radio. 
Just as an interesting side note, though we think of the vacuum tube radio as the predecessor to the solid state radio the crystal detector was actually a solid state diode and thus the solid state radio preceded the vacuum tube radio.
Amplification and oscillation were not possible with the diode vacuum tube.
Lee DeForest
Lee DeForest has been credited adding a third element called a grid to the vacuum tube and making what he called the “Audion Tube” which is the forerunner of the triode.
The grid is a wire mesh placed between the cathode and the plate. Electrons are able to flow past it with very little effect if it is not biased (bias means to apply a voltage). When a positive voltage is applied to the grid (positive bias) the electrons will flow faster and the plate current will increase. The grid will collect some to the electrons as the others pass by it and so there will be a grid current. Most of the time grid current is not desirable.
When a negative potential is added to the grid (negative bias) the electrons are
As the signal goes negative less current will flow through the tube causing the output voltage to go higher (tube resistance increases while R remains constant). As the signal goes positive the tube’s resistance decreases thus more current flows so the output voltage decreases.
repelled by the negative field around the grid wires and thus less will pass through the mesh. By increasing the negative potential the repelling effect will cause fewer electrons to pass. This effect will continue to increase as the negative bias is increased until the current is shut off completely. A very small voltage change on the grid can cause a large change in current flow inside the tube so amplification is possible. As the small signal goes negative it is added to the negative bias voltage and thus decreases the output, the plate voltage will go more positive, then when the signal goes in the positive the grid bias voltage will decrease so the plate current will increase causing the plate voltage do decrease so the small signal will produce a larger signal but with a 180 degree phase shift.
By taking some of the signal output and feeding in back into the input of the amplifier an oscillator can be constructed. This made it possible to create a continues wave (CW) oscillation which is the fundamental foundation of all ham radio, commercial radio, and any other radio communications
A new problem was added with the triode so that another element needed to be added but I will save that for the next post.
Vacuum Tube Power Diodes – 5U4, 5Z3, and 5R4 Popular in 1940s and 1950s
To start understanding the operation of the vacuum tube we must start with the diode meaning two elements or two electrodes. These two electrodes are the cathode and the anode more commonly known as the plate. There is the requirement of a heater which may also serve as the cathode but many diodes have the heater inside a sleeve so it will heat the sleeve which is the cathode. Though the heater is separate from the cathode it is not counted as an element.
As the cathode heats up to red hot the molecules are vibrating so vigorously they cause some to the atoms to lose electrons. These free electrons form an electron cloud around the hot cathode. When a negative potential is placed on the cathode the field will become greater, that is to say more intense and more electrons inter into the electron cloud.
If the cathode was not in a vacuum the electrons cloud would be dissipated by the gas molecules. Thus it is placed inside an evacuated envelope (glass or metal).
Typical Vacuum Tube Diode Construction. The schematic diagram shows the heater, also known as filament. Frequently the heater is not drawn. When the heater and cathode are one then it shows the upside down V, as in illustration, for both.
A plate is also included inside the envelope. The term plate, I fear, gives a miss conception of what it looks like. The plate is usually a cylinder that is placed around the cathode (see the above drawing). If a positive charge is placed on the plate the free electrons will migrate across the gap to the plate thus producing a current flow.This process is known as the Edison Effect.
The circled A represents an amp meter while the lines with – and + on each end represents batteries.
If a negative potential is placed on the plate that is negative with reference to the cathode thus leaving a positive cathode and negative plate current will not flow. This is the principle of rectification. The part of the cycle that causes the cathode to be negative and the plate positive current will flow but when the reverse happen and the plate is negative and the cathode positive current will cease thus turning the AC into a rippling DC voltage.
Full Wave Rectifier. Notice as one plate becomes negative with reference to the center tip the other will be positive so current would flow. When the voltage reverses the other plate will be positive and the current will then flow through that plate. Thus current flows during both half of the cycles. The filter and load are missing from this illustration but the electron flow would be through a load which is attached to the filter attached to one side of the cathode/heater.
When the diode is used to produce DC from AC filters must be added to eliminate the AC ripple. The raw DC output is a single diode will rise and fall as the AC voltage rises to a peak and then fall back to zero volts. Then there will be no current flow during the second half of the cycle. Thus if only one tube is used it is called a half wave rectifier. Four diodes can be used in a bridge rectifier circuit or by using a center tap on the transformer two tubes can be used to make a full wave rectifier. A smaller filter can be used when a full wave rectifier is used to produce a clean DC voltage.
Bridge Rectifier. As the voltage becomes negative on the top of the transformer it will be positive on the bottom. The third diode down will conduct current and the top diode will conduct forming a complete circuit through the load and filter.
The bottom diode and the second diode down prevents electrons flowing which will prevent a short circuit. When the voltage reverses then the opposite diodes will conduct. The filter consists of two chokes and two capacitors in a pi network configuration. The chokes store energy in a magnetic field which becomes stronger as the current increases then as the source voltage drops the collapsing field will reduce the amount of voltage drop reducing the ripple. The capacitors charge as the source voltage increases and then feeds voltage back as the source voltage drops. This how the filter turns the rippling AC to a clean DC voltage.
Vacuum tube rectifiers are not common in modern ham radio equipment but when I became an amateur radio operator in 1960 they were very common in new amateur radio equipment.
There is a lot of talk about the old days and vacuum tubes. It would seem that some hams think there is no place for the vacuum tube. It was recently that I was talking to my grandson, a radio technician in the U. S. Navy, and I asked him about the high power transmitters and he told me that they all had tube finals.
Collins 30L-1 Linear Amplifier
Looking through amplifiers to boost the power output from a transmitter or transceiver I was not able to find any solid state amplifiers above 400 watts. I am not saying there aren’t any and I did not do an exhaustive research but I did look at several sites, thumbed through QST and saw several amplifiers. So most modern amateur radio stations running 500 watts or more are using one or more vacuum tubes.
The vacuum tube is a simple device but I think they might make an interesting subject because for one there are still a lot in use in ham radio, whether in vintage equipment or power amplifiers. Reason number two there are a lot of new hams today who have had no experience with vacuum tubes and would just find them interesting. And finally reason number three is vacuum tube 
amplifiers are easy to understand and thus they make it easier for wanting to understand amplification and oscillation to learn the vacuum tube version first then the solid state will be much easier to comprehend.
So I have decided to do a series on the vacuum tube over the next few days.
12/20/2012 Sutter County California will have a simulated leave break and thus flooding. For this drill they asked for amateur radio participation. They did have one stipulation any ham radio operators participating must have completed the ICS 200b course. I am sure there are some who have to work that have completed the course and are thus not able to help but there are others who have the time but have not completed the course and thus are not allowed to participate.
The government agencies are getting serious about this. Some hams think their services will not be refused is a real disaster hits but do not kid yourself. They do not want people who do not understand the Incident Command System operational procedures to mess up the works. There is a very good possibility that ARES may require ICS 200b to be a member.
I would also recommend taking the ICS 700 and the ICS 100b.
We will only have 3 amateur radio operators at the drill and this makes amateur radio look bad. It makes the county officials question whether or not we will be able to help out in a time of real need.
To find the ICS 200 b course [CLICK HERE]
To fine the ICS 100 b course [CLICK HERE]
To find the ICS 700 course [CLICK HERE]
Do you know a ham radio operator you would like to buy a gift for but don’t know what to git? Here are a few suggestions:ham radio, amateur radio, gift, amateu
Maybe you are an amateur radio operator that knows someone who might buy a gift for you then you might direct them to this post.
For young people you would like to encourage to become an amateur radio operator here are few suggestions:
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