09-06-2020, 02:13 PM
(This post was last modified: 09-06-2020, 02:18 PM by Murphyv310.)
Hi.
They turned up today. They are slightly larger than other rod Pentodes, they have a larger diameter with four grooves in the glass envelope to no doubt stop deformation of the glass in severe heat and improve strength.
I've made a small test rig up to see what RF power can be obtained from these valves. I picked a random crystal and made up an oscillator using a 1j29. Then followed by a PA stage again using another 1j29 into a pi tank circuit to my RF power meter and dummy load. at 40v HT RF output just lifted the meter and using a 6.3v dial bulb lit it just above half brightness. Raising the HT to 100v made the bulb glow very brightly. Although hard to decipher on the meter I was getting around a watt. Parallelization of two valves doubles output to approximately 2 Watts. I now have tried one 1p24b, running with 150v at the anode it gives approximately 5 watts, it runs hot around 80c so I have no idea of life.
The circuit could be adapted for amateur radio QRP applications, assuming amateurs still construct projects.
Incidentally I added modulation and have to say quality is very good. I don't want to upload a circuit as this project could be used for non licensed use, it though was only made for the feasibility of these devices for RF low power circuitry.
Power supply is from 12v via two DC to DC converters for HT & LT. So if modified for amateur use it could be easily used as a portable or mobile TX.
They turned up today. They are slightly larger than other rod Pentodes, they have a larger diameter with four grooves in the glass envelope to no doubt stop deformation of the glass in severe heat and improve strength.
I've made a small test rig up to see what RF power can be obtained from these valves. I picked a random crystal and made up an oscillator using a 1j29. Then followed by a PA stage again using another 1j29 into a pi tank circuit to my RF power meter and dummy load. at 40v HT RF output just lifted the meter and using a 6.3v dial bulb lit it just above half brightness. Raising the HT to 100v made the bulb glow very brightly. Although hard to decipher on the meter I was getting around a watt. Parallelization of two valves doubles output to approximately 2 Watts. I now have tried one 1p24b, running with 150v at the anode it gives approximately 5 watts, it runs hot around 80c so I have no idea of life.
The circuit could be adapted for amateur radio QRP applications, assuming amateurs still construct projects.
Incidentally I added modulation and have to say quality is very good. I don't want to upload a circuit as this project could be used for non licensed use, it though was only made for the feasibility of these devices for RF low power circuitry.
Power supply is from 12v via two DC to DC converters for HT & LT. So if modified for amateur use it could be easily used as a portable or mobile TX.
