THE VOLTAGE DOUBLER

Doubling the DC voltage from a single wind secondary can be done. Say the secondary is 6 volts. To get 6 volts, a single diode wherein we only use half wave. To capture both , we need to use a bridge of 4 diodes. The difference is that we got twice the current with the bridge. The DC output will b the same at 6 volts. We can double the DC output by charging two similar capacitors in series, each being "charged" by a half cycle. The caps then are not charging at the same time but alternatively. But the charge is there and being in series, will add up to 12 volts! One end of the seconday line is connected to the junction of the two caps. The other end has two diodes to it with one putting out a +, and the other , a -. The plus goes to the pus of ghe upper cap., the minus to the lower cap. Will tr

y to upload a diagram.

2 tube radio with 1n34 detector

Now, let us study the first tube in details. It is set up as an oscillator and mixer. Look at the osc coil with a tap. The Cathode goes to the tap to gets its ground. But the long side of the coil goes to a grid.So, the tube goes into an oscillation. The frequency is controlled by a variable capacigor anged with the tuner to the antenna coil. The antenna coil is fed into a grid to mix its signal with the local osc. The plate is in series to the primary of the first IFT. The second tube is a straight forward RF amp which amplifies only the 455 Khz intermediate frequency. This makes the radio selective.

2 tube radio

SUPERHETERODYNE RADIO WITH JUST 2 TUBES

Most if not all of us in the chat group are already verify familiar with tube amps. No need for further lessons here. Besides, the hybrid tube amp has for its final amp, an IC. We can limit the tubes to the essential to make a superhet radio. Just 2 tubes. We all have tube amps to amplify the audio. 1. Just use the first two tubes,either the SA and the SK or the BE and BA. 2. Use a 1 amp power supply traffo, 6 or 12 V. 3. The RF tubes do not need a HV, the 12 V secondary an be by putting a voltge double. Or back to back another traffo to get 110 volts isolated. Those 110 volts adaptor will do if the amperae is sufficient. If you an old ps of the Epson printer, it is 32 volts. 4. No need for the rectifier tube then. 5. Audio amp can be a existing tube amp.,or put an IC amp for the audio amp. No need for he power amp tube. 6. The detector cum triode tube can be eliminated, Just use an 1n3 detector diode.

The Tuned Radio Frequency receiver

Armstrong Superheterodyne receiver.

The problem with the Regen radio was that it was fidgety and lacked selectivity. The next type of tube radio then was called the TRF for Tuned radio frequency. The idea was a series of amplifiers each with a tuning coil. There were just too many tuners! But it can fine tune to a station. It was still figedty to the taste and something has to be developed to make a USER FRIENDLY radio. Armstgrong went back to the drawing board. He knew the principle that frequencies can be MIXED. His goal was go reduce the number of tuning condensers. Finally, he invented the SUPERHETERODYNE radio when a local oscillator is mixed with the incoming signal. The tuning capacitors of the antenna coil and the oscillator coil were ganged. The differential frequency was kept constant at 455 Khz. The next amplifier as tightly tuned to 455 Khz. Till today, this principle is still used. Superhets spread all over the world and in the U.S.A., the most common was a five tube set up. It was called the All American 5 or AA5. ?The firs tube was mixer-oscillator, the second tube was the IF amplifier, the 3rd tube was a diode-triode combo and finally the power amp. A fifth tube was the rectifier.

Description. In 1913 Major Edwin H. Armstrong patented a design for the Regenarative Receiver that uses the principle of positive feed-back in amplifiers to demodulate AM, CW, SSB, and FM. Mr. Armstrong's circuit is shown and used the new vacuum tube of the time. The Regenerative receiver has since become the most popular basic receiver for Amateur Radio Operators and Electronics experimenters worldwide. The principle of operation is simple. Positive RF feedback is used to increase the RF gain of the amplifier up to and beyond self-oscillation. With no input RF signal the internal noise peaks and a small bias voltage combine to produce a stable but self-limiting oscillator, except right at the peak of oscillation very high gain is produced and the detector becomes very sensitive to small input RF signals, like those associated with SSB and CW. AM is demodulated just below the point of oscillation, but SSB and CW are demodulated when an RF signal combines with the heterodyne signal to produce an audible beat tone. Today the basic Armstrong circuit remains the same.

3/1/20 Hi tube enthusiasts interested in RF with tubes. A brief: -Edison invented the light bulb. -Fleming of UK imported Edison's bulbs. -Fleming played with a bulb and placed a second element inside. -Using batteries, he discovered electrons moved inside the bulb. Eureka! The DIODE! -Back in the U.S.A., a third element was discovered to control the flow of huge electrons with TINY currents. EUREKA! THE TRIODE. It was originally called the AUDION. So, it is CATHODE,GRID,PLATE. -Electrons moved fast inside the tube, i.e. at high voltage, 45 volts upwards. Armstrong, American, was first to experiment RF in a tube. He used the basic t riode as an RF amplifier. He invented the REGENERATIVE RECEIVER. The Audion was an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest in 1906. It was the first triode, consisting of an evacuated glass tube containing three electrodes: a heated filament, a grid, and a plate.