This is a one valve [tube] radio that believe it or not I constructed 48 years ago. It remained lost but was discovered again during a recent house move. The valve used is a battery R.F. pentode dating from around 1948 on a B7G base. The type number is DF91 or the American equivalent, the 1T4....

Observations of electromagnetic (radio) signals on very low frequencies, 0 KHz - 10 KHz. Observed 10 may 2008, approx. 23.00 hour on 4,5. KHz: next to the original radio resonance of 4,5 KHz there is another resonance (spectrum on approx. 10 KHz), that comes in and fades away after 30 minutes....

The 211 Transmitting Tube is a high-power vacuum tube. Because of the power this tube requires general tube testers are not able t The 211 Transmitting Tube is a high-power vacuum tube. Because of the power this tube requires general tube testers are not able to interrogate this tube. I have...