A magic eye tube or tuning indicatorin technical literature called an electron-ray indicator tube is a vacuum tube which gives a visual indication of the amplitude of an electronic signal, such as an audio output, radio-frequency signal strength, or other functions. Its first broad application was as a tuning indicator in radio receiversto give an indication of the relative strength of the received radio signal, to show when a radio station was properly tuned in.
The magic eye tube was the first in a line of development of cathode ray type tuning indicators developed as a cheaper alternative to the needle movement meters.
It was not until the s that needle meters were made economically enough in Japan to displace indicator tubes. The magic eye tube or valve for tuning radio receivers was invented in by Allen B. DuMont who spent most of the s improving the lifetime of cathode ray tubesand ultimately formed the DuMont Television Network.
The RCA 6E5 from was the first commercial tube. The earlier types were end-viewed see the EM34usually with an octal or side-contact base. Later developments featured a smaller side-viewed noval B9A based all-glass type with either a fan type display or a band display see the EM This design prompted the contemporary advertisers to coin the term magic eye, a term still used.
The function of a magic eye can be achieved with modern semiconductor circuitry and optoelectronic displays. The high voltages Volts or more required by these tubes are not present in modern devices, so the magic eye tube is now obsolete.
A magic eye tube is a miniature cathode ray tube, usually with a built-in triode signal amplifier. It usually glows bright green, occasionally yellow in some very old types, e.
It is used in a circuit that drives the grid with a voltage that changes with signal strength; as the tuning knob is turned, the gap in the eye becomes narrowest when a station is tuned in correctly. Internally, the device is a vacuum tube consisting of two plate electrode assemblies, one creating a triode amplifier and the other a display section consisting of a conical-shaped target anode coated with zinc-silicate or similar material.
The display section's anode is usually directly connected to the receiver's full positive high tension HT voltage, whilst the triode-anode is usually internally connected to a control electrode mounted between the cathode and the target-anode, and externally connected to positive HT via a high-value resistor, typically 1 megaohm.
When the receiver is switched on but not tuned to a station, the target-anode glows green due to electrons striking it, with the exception of the area by the internal control-electrode.
This electrode is typically V negative with respect to the target-anode, repelling electrons from the target in this region, causing a dark sector to appear on the display. The control-grid of the triode-amplifier section is connected to a point where a negative control voltage dependent on signal strength is available, e.
As a station is tuned in the triode-grid becomes more negative with respect to the common cathode. The purpose of magic eye tubes in radio sets is to help with accurate tuning to a station; the tube makes peaks in signal strength more obvious by producing a visual indication, which is better than using the ear alone.
The eye is especially useful because the automatic gain control AGC action tends to increase the audio volume of a mistuned station, so the volume varies relatively little as the tuning knob is turned. The tuning eye was driven by the AGC voltage rather than the audio signal. When, in the early s, FM radio sets were made available on the UK market, many different types of magic eye tubes were made available, with differing displays, but they all worked the same way.
Some had a separate small display to light up indicating a stereo signal on FM. The British Leak company used an EM84 indicator as a very precise tuning-indicator in their Troughline FM tuner series, by mixing the AGC voltages from the two limiter valve grids at the indicator sensing-grid.AGC Plumbing can fix your leaking tap or pipe quickly and efficiently.
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Trust in AGC Plumbing to fix your leaking pipe issues. For leaking tape and pipe repairs or replacement installations, contact AGC Plumbing. We come to you, no matter where you are in the Sydney Metropolitan area, and our friendly plumbers can assess and fix your problem with ease! Request a Quote.In a Facebook post last night, Chan described having her statement being recorded tomorrow as a "belated Valentine's Day date" with Bukit Aman.
That is all I am asking for. That is what most Malaysians had asked for. Chan, who was formerly a federal counsel with the AGC, said someone filed a police report against her over the expose because she had raised questions about political interference in a supposedly independent institution.
She said the democratic values of transparency, non-political interference and responsible freedom of speech were the same ideals bandied by Pakatan Harapan for many years. Harapan's promises of greater freedom of speech and accountability are broken. But it seems that the plot is now lost.
Leaked AGC email – cops call in MCA's Chan for questioning
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Malaysiakini is providing free access to the most important updates on the coronavirus pandemic. You can find them here. Published 14 Febam. Related Reports. Home Ministry and AGC must drop objections to citizenship for stateless children. Lawyer roasts AGC on 'missteps' leading to Najib's trial postponement.
AGC drops 'middle finger' charge against Siti Kasim. Kit Siang: Barbershop bungle shows ministerial disconnect. AirAsia boss hopes customers accept credit instead of refund. Trump likes virus briefings, some advisers worry he likes them too much. Job Vacancies. VOIZ Asia. FG Media.Automatic volume control AVC, or automatic gain control AGC, as it is sometimes called, is a system for keeping the volume from the loudspeaker at a constant level, no matter what the strength of the high-frequency signal strength may be.
Manual volume control - ie, by hand - is usually fitted even on sets provided with automatic volume control, since although it may be desirable that all stations should come in at the same strength on the loudspeaker, yet one obviously wants to be able to control that strength to suit personal requirements. The main object of AVC is to make it unnecessary to keep altering the manual volume control as one passes from station to station.
In the ordinary way, one may readily receive a local station at tremendous strength, while a few degrees away on the dial another station may be comparatively weak. As one tunes still farther round the dial, a very powerful station may produce a most unpleasant blare. There is an obvious advantage if all the stations can be brought in at full loudspeaker strength, but no louder and no weaker. For Tuned Radio Frequency TRF or straight sets this is done by altering the sensitivity of the whole set, either on the high-frequency or on the low-frequency side, or on both; while in the case of super-heterodynes, detectors and intermediate frequency amplifiers may also have their sensitivity adjusted to increase or decrease the sensitivity of the set as may be required.
In many wireless sets were home constructed and simple TRF sets were the norm. Also the BVA restrictions on multiple valves and the tax on the number of valve-holders in a commercial set also kept the TRF as the main design philosophy. Thus many types of detection were in use and in the book Scott-Taggart describes them.
As the s progressed and the superhet became the standard model of receiver design most sets were commercially manufactured and the complexity of setting-up was taken care of with professional equipment. Thus having a double diode triode at the end of the IF chain became standard. However, in the s an interesting method of AGC and demodulation was based on a special valve as follows.
A special valve has been developed in America for AVC work, and the circuit is illustrated above. The valve consists of two grids G 1 and G 2which are interlinked so that each is the same distance from the filament, and between that electrode and the anode.
The grids are, therefore, symmetrical, and each end of the tuned circuit is connected to a grid, while the middle point of the inductance is connected through the grid leak R and capacitor C to the filament. The operation of the arrangement is as follows:. The two grids and the filament form a full-wave rectifier, which supplies a generous rectified current, which passes through the resistance R.
The result is that a fluctuating potential is set up across R corresponding to the LF current from the microphone at the transmitting station, and these LF potentials are applied to both grids.
As far as LF is concerned, therefore, the two grids are given the same potential variation, and as they are interlinked although not touching, of course they act in the same way as would a single grid, and produce an amplified low-frequency current in the anode circuit of the valve.
Use of the double-diode triode is illustrated in above where one of the diodes of the double-diode is utilised for AVC, while the other is used as a diode detector. It will be seen that the anode A 2 is connected to the top end of the inductance, the bottom end of which is connected to the usual 'grid leak' R 5 of, say, 0.
A tapping is taken on the resistance R 5 to the grid of the valve. This is simply the ordinary arrangement of a diode followed by an LF amplifier. The tuned circuit, however, also feeds the anode A 1 through a fixed capacitor of 0. The anode A 1 is now connected through a resistance R 2 and a bias battery B to the cathode. When the input high-frequency current communicated to A 1 exceeds the negative voltage of the bias battery B, an electron current will flow from the anode A 1down the vertical thick line in the diagram through the resistance R 2 and round to the cathode.
In doing so, there will be a DC component flowing through R 2and use of this rectified carrier-wave is made by filtering out the LF variations by means of a resistance R 3 and a capacitor of, say, 0. The circuit is quite simple to understand if one divides it in this manner. The object of the bias battery is to provide an initial voltage on the anode A 1so as to produce a delayed AVC action which comes into force only when signals reach a predetermined value.
The bias voltage is adjustable, and in practice would be derived from a potential divider usually a moving contact on a se1f-bias resistance.One response was that the tradesman had left who had taken the images with his phone I phoned another company and they were there the following day.
I would not bother calling this company nor would I recommend them. Hi Julia, It sound like we have not carried out any work for you, is that correct?. I am sorry Tim failed to get back to you regarding an appointment.
Please feel free to contact me directly and I wil Read more. Thank you for your response but I couldn't wait any longer. I have since contacted another company and I am happy with their quote and Im proceeding with them.
No problem, thank you for the feedback Julia. Very quick to do a quote and turn up for job but after that they are impossible to pin down and come back to rectify ongoing problems. Lots of promises by receptionist but they just fail to come back. Worst tradesmen I have come across.
I am sorry to hear that you did not have a good experience with AGC Roof. It is unfortunate that you have decided to create an email address with agc in it to create this post and not use your genuine After a little rain it appears that the eves were inundated and fell to the ground.
Very disappointed. Hi B Black, We do not recognize the building in your attached pic as a site we have recently worked on. If this is a genuine complaint please get in touch with our customer service team to resolve you It is very disappointing B Black that you have not removed your post despite the fact that your strata manager has explained to you that at the time you posted your pic and post, the works were not actually completed!
Worst customer service I have ever dealt with. I was hung up on after numerous times to book in a time, which should not be difficult.It is non-flammable, does not corrode metals easily, and is one example of solvents that offers the highest degreasing performance of chlorinated organic solvents. Two grades are available: AL alkali type and NE neutral type. It can also be used as a substitute for brominated solvents for which regulations and controls are expected to tighten.
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