UNDERSTANDING THE RIFE/BARE RF SYSTEM
Many researchers have been experiencing problems with their Rife/Bare tubes failing to stay lit at some modulation frequencies. Problems with unstable VSWR readings have also been reported when the modulation frequency is changed To understand why these problems occur and to be able to correct them in a logical and effective manner, it is necessary to understand what is happening in the Rife/Bare system as far as the RF energy is concerned. Accordingly, a series of tests was made to determine the factors which characterize the operation of a typical Rife/Bare tube.
Tests were made using a digitally modulated RF system capable of being adjusted to any desired RF output level between 0 and 700 watts. A carrier frequency of approximately 28.82 mHz was used for these tests. Modulation frequencies between 0 and 200,000 Hz were used.
A GT-310 frequency generator card installed in a 386/DX-40 computer was used to provide the modulating frequencies, as well as the 5 mHz (approx.) frequency which was injected into the external VFO input of the RF source to provide the RF carrier.
The RF source used for these tests was a Yaesu Musen FLdx-400 amateur radio band transmitter, which is capable of operation on any of the amateur radio bands between 3.5 and 30 mHz, with a power output of up to 120 watts.
The signal from the FLdx-400 was sent to a Heath Warrior amplifier, which is capable of producing up to 700 watts output on all amateur radio bands between 1.8 and 30 mHz. This amplifier could be switched in or out of the system as required.
The amplified RF signal then goes to a Heath SA-2060A antenna tuner. This tuner is a standard Pi-network tuner, consisting of a parallel capacitor / series coil / parallel capacitor network, and will match wide ranges of load combinations. It is rated at 1000 watts continuous power operation. The tuner has a built-in VSWR / Power meter.
A Palomar M-527 instantaneous reading VSWR meter was also used to determine the peak VSWR during operation.
Several Rife/Bare tubes were used during these tests. With only slight variations, the test results were virtually identical, regardless of the tube used. All tubes measured 30 inches overall, in length, with diameters between 25mm and 10mm. The gas fill used is Argon/Neon in a 90/10 mixture at a pressure of between 12-14mm Hg. Power was fed to the tubes under test using my Twisted Transmission Line balun. The tube was mounted in a shielded tube enclosure. For test purposes, the screened cover was not used, so as to make it easier to get to the tube for adjustments. No difference in data was noted when the cover was replaced on the enclosure.
We may consider that a properly operating Rife/Bare unit is a system composed of a radio frequency energy generator, (Transmitter / Amplifier), an impedance matching device, (Antenna tuner), and a load which absorbs the RF power (The Rife/Bare tube). The standard Rife/Bare system may be compared to a broadcast station, although the Rife/Bare system is not designed to radiate the RF energy as a broadcast station does. The big difference which sets the Rife Bare system apart from our broadcast station example is that a broadcast transmitter looks at a constant load - the antenna - while a Rife/Bare transmitter looks at a load which is not constant - the Rife/Bare tube.
In order to obtain the maximum RF energy transfer between the transmitter and the load, it is necessary that the impedance of the load match the output impedance of the transmitter or final RF amplifier. Generally, this load value is specified by the transmitter or amplifier manufacturer as being 50 Ohms impedance, resistive, with j=0. j is the notation for the value of reactance, either capacitive or inductive, and is expressed in Ohms.
This means that that the transmitter wants to be connected to a 50 Ohm resistance, with no capacitive or inductive reactance. In theory, this is possible; in practice, it is nearly impossible, because all real components have some amount of inductance or capacitance - or both - in addition to their load resistance. If excessive inductive or capacitive reactance is present in the load, it may cause the amplifier to deliver less than its rated power; to draw excessive DC power; and, in the case of transistorized amplifiers, possibly overheat the amplifier to the point of destruction.
An inductive reactance is shown as a positive value of j; a capacitive reactance is shown as a negative value of j. For instance, j = +10 would refer to an inductive reactance of 10 Ohms, and j = -20 would refer to a capacitive reactance of 20 Ohms.
The resistive component of a load absorbs power and converts it into useful output; light, heat, motion, etc. This power component of the load is called the Real Power, and we try to maximize it.
The reactive component of a load causes unwanted RF current to flow through the system, but this reactive current flow is not converted into any useful output. Instead, the reactive RF energy is reflected from the load and returned to the generator (amplifier). This circulating current causes heating of components due to I*R losses, that is, heating caused by loss of RF energy in the normal circuit resistance. This power component of the load is called Reactive Power, and we try it minimize it.
To an RF designer, the Rife/Bare tube is an interesting device. It represents a varying load, with constantly changing characteristics. Because of this, the problem of matching the Rife/Bare tube to an RF power amplifier is not at all trivial, especially at high power levels. For the purposes of this article, I shall confine my discussion to those systems which feed RF power to the Rife/Bare tube by using external electrodes placed around the tube. Electrodes of this type include, but are not limited to, spiral wrapped wire, clamps, and copper pipe couplings. Insulation between the tube and the electrodes or on the spiral wrapped wires does not affect the operation as far as this discussion is concerned.
In an ideal world, the Rife/Bare tube would represent a pure resistance, which would make the amplifier (and the RF designer) quite happy. But, this is the Real World, and things dont work that way. During its operating cycle, the Rife/Bare tube may exhibit a load ranging from pure capacitance at one end, to low resistance, to a combination of capacitive and inductive reactance at the other. To make the problem of matching the tube to the amplifier even more difficult, the operating characteristics of the tube depends on such things as the tube temperature, the peak power level applied to the tube, the instantaneous peak RF voltage present at the tube electrodes at the beginning of the modulation pulse, and the maximum RF voltage and current at the tube electrodes during the modulation pulse. In most cases, the best we can do is to try to find a reasonable operating condition which transfers as much RF energy as possible to the Rife/Bare tube while not harming the amplifier.
The typical Rife/Bare tube is connected to the RF source by using external electrodes around the ends of the tube. Let us consider the two extremes of operation of the Rife Bare tube:
In the first case, the tube is not lit at all. This means that the tube is essentially invisible to the RF system - its just not there!
In the second case, the tube is 100% conducting. In practice, the tube never actually gets to this point, because we cant pump enough RF into the tube to ionize all the gas without vaporizing the tube. (Think: Lightning!) If the tube ever reached that point, then for purposes of analysis, it could be replaced with a metal rod of the diameter of the gas column.
What does this mean for the RF designer? The first case cited above, if what the tube looks like to the RF system just as the RF appears at the tube at the start of the modulation pulse. The second case (which we never quite reach) is an rough approximation of what happens during the modulation pulse when the tube is lit.
Of the two cases of operation of the Rife/Bare tube previously described, the second case is of primary interest to this discussion because whenever the tube is lit, it is in a conducting state, and therefore the RF system sees the Rife/Bare tube.
As I mentioned previously, the amplifier wants to see a resistive load, with no reactance. The Rife/Bare tube is a complex load, that is it contains both resistance and reactance. The primary components of the Rife/Bare tubes complex load are:
a) The resistive part of the load, represented by the power absorbed by the ionized gas column in the tube. It has been determined that the resistive component ( a ) varies inversely with the applied RF power level. The resistance of the tube is lowest at high power levels. This is because as more of the gas becomes ionized (conductive) it can carry more current with the same applied voltage at the electrodes. Think of it as many very small diameter tubes all connected in parallel. The higher the power, the more tubes are in the circuit. Conversely, at low power levels, the tube resistance is higher. When the tube is not lit at all, the resistance of the Rife/Bare tube is infinite. At that point, a very high RF voltage is required at the electrodes to start the tube. After the tube is lit, a smaller voltage at the electrodes will maintain the discharge in the tube.
b) The capacitive reactance between the external tube electrodes and the ionized gas column inside the Rife/Bare tube.
This virtual capacitor is formed with one plate of the capacitor being the external electrode, and the other plate of the capacitor being the ionized gas in the tube and directly beneath the external electrode. The glass tube wall is the major component of the dielectric in this capacitor. Obviously, there is one such virtual capacitor at each end of the Rife/Bare tube.
It has been determined that the capacitive reactance component ( b ) remains essentially constant during tube operation, showing a slight decrease in reactance as the RF power applied to the Rife/Bare tube is increased.
Since the gas will first ionize closest to the electrode, and then grow from that point as the applied RF power increases, the spacing between the electrodes will tend to remain pretty constant during all portions of the tube operating cycle. This will tend to cause the capacity and therefore the capacitive reactance of this virtual capacitor to remain fairly constant.
c) The inductive reactance of the ionized gas column in the tube.
Because the ionized gas column in the Rife/Bare may be likened electrically to a straight length of wire, the inductance and the inductive reactance of the Rife/Bare tube will approximate that of a straight piece of wire having the same length and diameter of the ionized gas column in the Rife/Bare tube. Although the inductance of a conductor does change slightly with variations in diameter, (it gets less as the wire gets larger in diameter) the change is negligible for tubes at least as long as 18 inches.
It has been determined that the inductive component ( c ) also remains fairly constant during operation, showing a slight decrease in reactance as the RF power applied to the Rife/Bare tube is increased.
The net result is that the complex load the Rife/Bare tube presents to the RF system is a combination of the desired load resistance, and the difference between the j+ and the j- reactances of the tube.
In the system described here, the j value was negative under all conditions of measurement. In summary, the tube behaves as a load resistor having a negative resistance change with increasing power, and which has some capacitive reactance.
What does this imply for the operator of a Rife/Bare system? In a nutshell, it says that there will not be a single setting of the antenna tuner that will be correct for all power levels. It also says that low power units - below about 100 watts - will be more difficult to keep adjusted. It will also be much harder to light a Rife/Bare tube when using a unit which has a low power output.
First of all, they dont tune anything. What they are is conjugate matching networks. That is, when they are properly adjusted, they will pass power from one device to another, in either direction, with equal efficiency, and at the same time cancel out any inductive or capacitive reactance existing in the source or loads connected to the tuner.
Internally, most tuners consist of two variable capacitors and either a variable coil or a tapped coil with a switch. The first capacitor is connected between the input connector and circuit common (ground or earth connection), and one end of the coil. The second capacitor is connected between the output connector and circuit common (ground or earth connection), and the other end of the coil. That places the coil in series between the input and output connectors. The schematic diagram looks somewhat like the letter Pi, and so these tuners are often referred to as being Pi-net(work) tuners.
Without going into a plateful of mathematics, suffice to say that there are normally many different settings using the three adjustable elements of a Pi-net tuner that will match a source and load. Note that some of these settings allow a wider bandwidth than other settings. For Rife/Bare service, you want to use a setting that gives you the easiest starting of your Rife/Bare tube - note that this is not necessarily the best bandwidth setting of the antenna tuner.
Balanced means that both sides of the transmission line have equal but opposite voltages when measured against ground. An example of a balanced line is 300 ohm TV twinlead.
Unbalanced means that one side of the transmission line is connected to ground, and the other side of the transmission line it at an RF potential when measured against ground. An example of an unbalanced line is coaxial cable.
Connecting a balanced line to an unbalanced line will result in some of the RF energy flowing on the outside of the coax cable shield and being radiated away into space.
To connect a balanced line to an unbalanced line, a device called a Balun is required. BALUN stands for BALanced to Unbalanced line transformer. The original balun simply converted a balanced line (parallel wire transmission line) to unbalanced line (coaxial cable). Baluns may be designed for impedance transformation as well, for instance, a 4:1 balun will convert 50 ohms coax cable impedance to 200 ohm impedance using parallel wire transmission line.
The original balun design used sections of transmission line for the impedance conversion process. Later, it was found that coiling the parallel balun lines was possible. Doing this saved space and helped to reject common mode current flowing back from the load. Winding the transmission line on a ferrite core greatly improved the operating frequency range of the balun, but introduced some limitations in actual use.
Ferrite core Baluns are one of the most misunderstood of components, even by those with many years of RF experience. Although simple in construction and appearance, they have serious limitations, which, if not understood, will cause distortion, heating, and low power output from your Rife/Bare system.
Ferrite core baluns are very useful devices, but they will cause problems if they are operated into a highly reactive load, such a Rife/Bare tube. What will happen is that the reactive currents flowing in the balun windings will cause the ferrite core to magnetically saturate, and this in turn, will cause heating of the core material as well as serious waveform distortion of the RF signal. In simple words, the balun overheats and the tube does not get as much power as it should.
As you know, if you have visited the other Rife pages on this web site, I have devised what I call my Twisted Transmission Line (TTL) balun. This is simply a parallel line balun which is coiled up to reduce common mode currents. The advantage of this type of balun over a conventional ferrite core balun is that the TTL balun has no core to saturate, and so will operate properly at power levels where the ferrite balun would burn up. Note that the TTL balun also has losses, which show up as heating of the wire. For this reason, Teflon insulation is used on the balun wires to resist the heat during operation.
In general, a Rife / Bare tube will exhibit a series of color and appearance changes as the power level and modulating frequencies are varied. On all of the Argon / Neon mixture tubes I have tested, the following description is what I have observed in all of them. For the purposes of this discussion, it is assumed that a standard external spiral wrapping similar to that shown in Dr. Bare's book is used to feed the RF power to the tube. The appearance is similar when you are using either unmodulated RF or modulated RF, if the modulating frequency is below 1000 Hz.
At very low power levels applied to the tube, the gas glow first begins near the electrode wrapping, usually appearing first at one end of the tube. At this point, the VSWR is usually quite high and the discharge column is unstable, exhibiting beading and flickering. The bead pattern will change with the modulating frequency. It will also be influenced by external objects near the tube. This region of operation is characteristic of a tube with insufficient RF power applied for proper operation.
As the power is increased, the glow begins to extend across the length of the tube, eventually connecting to the glow discharge at the opposite electrode. As soon as this occurs, the VSWR decreases, and the discharge usually stabilizes, appearing as a soft, transparent column of light. The color is a Mauve to Purple or Violet in the center of the column, fading to a pale blue at the outside of the discharge column. (to me, the color appears to be Violet.)
Raising the power even further causes the center core of the discharge to expand and become brighter. Eventually, the Violet center color expands to fill the entire diameter of the tube. During this time, the VSWR remains fairly constant, although slight retuning of the antenna tuner is needed for the lowest VSWR. In this region of operation, the optical output of the tube tracks the RF power applied to the tube closely.
Further increases in power result in a change in color of the discharge. The Violet color will become a Purple-White, with a trace of Blue mixed in. This causes the spectral output of the tube to change, with more energy appearing in the red end of the optical spectrum. The luminous efficiency of the tube also increases somewhat in this region of operation. The VSWR changes slightly, usually requiring adjustment of the antenna tuner for lowest VSWR.
Operation at these high power levels can cause overheating of the tube and possible damage due to overheating of the glass under the electrodes, with subsequent tube wall failure. The increased heating of the gas in the tube can raise the tube wall temperature high enough to drive off adsorbed gasses and contaminate the tube, rendering it unstable in operation; hard to light, and producing a "dirty" color when running. Quite often, a tube overheated this way will recover normal operating characteristics if left to "rest" for a few days.
The question has been asked, "How many watts do each of these regions of operation represent?" And the answer is; "It depends!" It depends on your particular setup, and how effectively your system delivers the RF power to the tube. Some systems will generate a higher peak RF voltage to the tube at the instant of lighting the tube; these systems will generally produce a brighter discharge at low to moderate power levels (10-100 watts). For operation at higher power levels, peak RF voltage is less critical than proper RF power transfer when the tube is fully lit. Losses in the tuner, connecting cables and balun can rob an otherwise good system of much of its effectiveness.
The choice between amplifier types is not yet clear, as to whether or not they make a difference in the biological effectiveness of the Rife / Bare system. What is known from an engineering standpoint, is that they behave quite differently when used in Rife / Bare service.
An RF amplifier, including the ones commonly used for Rife / Bare systems, are designed to supply energy to a "matched" load. That is to say that the load (the device accepting the power from the amplifier) has the correct resistance and reactance values to match the amplifiers design so that it accepts all the power the amplifier sends to the load. If the load is "mismatched", that is to say, it has resistance or reactance values which are different from what the amplifier expects, then part of the RF energy reaching the load will be "reflected" or sent back to the amplifier. This reflected power can cause damage to the amplifier if it is great enough. As mentioned previously, the Rife / Bare tube is a terrible load as far as the amplifier is concerned, because its characteristics vary over a wide range as the tube goes on and off during the modulation cycle. Because of this problem, amplifier design and matching is a serious concern for operators of Rife / Bare systems.
Vacuum tube amplifiers by their nature use high voltages in their operation, while transistorized amplifiers use low voltage. This fundamental difference makes their operation under Rife / Bare use quite different. In general, we may summarize the differences between the two types of amplifier design as follows:
|Vacuum Tube Amplifier||Transistorized Amplifier|
|Internal Voltage Used||High (300 - 3000)||Low (12 -48)|
|Cooling Requirements||Large Fan Needed||Small Fan Needed|
|Peak RF Voltage Out to Fire R/B Tube||High||Low|
|Resists Damage in Operation||Excellent||Poor|
|Power Supply Weight and Size||Heavy / Large||Light / Small|
|Suitability for R/B Service||Excellent||Fair to Good|
Generally, vacuum tube amplifiers will work better for high power levels, due to their ability to handle Misadjustment during operation. This also makes them ideal for experimental and research use where the operating conditions may vary widely from the ideal. At low power levels, they also have the advantage of being able to generate higher peak RF voltage levels, which makes lighting the tube easier.
Transistorized amplifiers are excellent for lightweight, portable units, which are designed to operate at a specific operating point(s) and under fairly well controlled conditions. They are also lighter and smaller, and will operate on batteries if necessary. Because they do not withstand abuse as well as vacuum tube amplifiers, the design of the entire Rife / Bare unit must be more carefully controlled.
In general, the following procedure will work for adjusting any antenna tuner of the Pi network configuration when used with a Rife/Bare tube. This procedure assumes that you have a reasonably stable RF amplifier which may be operated a close to full power without damage as the tuning procedure is accomplished. If your amplifier cannot do this (check the instruction manual) then it is advised to do the initial tune up at a reduced power level, then increase to the power level you are going to use during normal operation.
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