It would be nice to make a Hartley oscillator with an electron tube that operates at only 6V.
It may be possible by canceling the self assumed negative grid voltage using a high Megohm resistor from plate to grid. The same technique that is used on the Pleiades V series microphone pre preamplifiers for low noise and battery operation. Deliberate reduced heater voltage may be used too to reduce noisy electron cloud near grid as explained on previous euroelectron posts.
Using grid leak bias a very low noise and pure sinewave oscillator may be made. Can the high Megohm resistor play this role too stabilizing gain by automatic gain control. On the Neumann U47 the much higher Megohm resistor provides automatic gain control and it is connected from grid to ground.
How about an audio frequency oscillator like this, one oscillator for each musical note. Intonation can be great by tuning correct to the human mind high octaves which need to be stretched in frequency for correct musical pitch.
An RF front end preamplifier could be made using the same principles. Reduced anode voltage and heater voltage makes a very quite preamplifier. If it can hear the subtlest and quietest sound of the human voice from a ribbon microphone with very low hiss why should it not pick the furthest faintest radio signal from space?
A simple receiver could be initially tried with 2 aluminum foils separated by an A4 paper for dielectric. In parallel connected could be 60turns wound on kitchen paper bobbin. A capacitor coupling to the electron tube grid. The other side of the coil capacitor combination to ground and cathode. A high Megohm resistor from anode to grid. An output transformer from battery plus to anode. The cathode connected to ground. The secondary of the output trasformer to a mic input. Antenna connected to the coil. Underheated cathodes, optimum temperature (heater voltage) found by experiment. A regenerative receiver would be interesting as such a low noise electron tube topology feeding back to itself may produce lesser noise and high sensitivity.
A suitable tube is a triode connected EF183 as on the Pleiades V series pre preamplifiers.
It may be possible by canceling the self assumed negative grid voltage using a high Megohm resistor from plate to grid. The same technique that is used on the Pleiades V series microphone pre preamplifiers for low noise and battery operation. Deliberate reduced heater voltage may be used too to reduce noisy electron cloud near grid as explained on previous euroelectron posts.
Using grid leak bias a very low noise and pure sinewave oscillator may be made. Can the high Megohm resistor play this role too stabilizing gain by automatic gain control. On the Neumann U47 the much higher Megohm resistor provides automatic gain control and it is connected from grid to ground.
How about an audio frequency oscillator like this, one oscillator for each musical note. Intonation can be great by tuning correct to the human mind high octaves which need to be stretched in frequency for correct musical pitch.
An RF front end preamplifier could be made using the same principles. Reduced anode voltage and heater voltage makes a very quite preamplifier. If it can hear the subtlest and quietest sound of the human voice from a ribbon microphone with very low hiss why should it not pick the furthest faintest radio signal from space?
A simple receiver could be initially tried with 2 aluminum foils separated by an A4 paper for dielectric. In parallel connected could be 60turns wound on kitchen paper bobbin. A capacitor coupling to the electron tube grid. The other side of the coil capacitor combination to ground and cathode. A high Megohm resistor from anode to grid. An output transformer from battery plus to anode. The cathode connected to ground. The secondary of the output trasformer to a mic input. Antenna connected to the coil. Underheated cathodes, optimum temperature (heater voltage) found by experiment. A regenerative receiver would be interesting as such a low noise electron tube topology feeding back to itself may produce lesser noise and high sensitivity.
A suitable tube is a triode connected EF183 as on the Pleiades V series pre preamplifiers.
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