À la nuvistor

[Esteban]

I have four or five 6CW4... Maybe can be useful. I think nobody build a MD based on this small tube (only 1.5 cm!). This is low noise and cover HF part of band. I had in past a Japanese TV (Hitachi) in wich front part was words "With Nuvistor". I check it and found the tube in the tuner. Also I remember the stability of the image...

[Qiaozhi]

Originally Posted by Esteban

I have four or five 6CW4... Maybe can be useful. I think nobody build a MD based on this small tube (only 1.5 cm!). This is low noise and cover HF part of band. I had in past a Japanese TV (Hitachi) in wich front part was words "With Nuvistor". I check it and found the tube in the tuner. Also I remember the stability of the image...

Have a look here ->
http://www.thevalvepage.com/valvetek...r/nuvistor.htm

There are some example circuits that might be useful.

[Esteban]

Originally Posted by Qiaozhi

Have a look here ->
http://www.thevalvepage.com/valvetek...r/nuvistor.htm

There are some example circuits that might be useful.

Thanks very much, very interesting article! I found a power supply for + B, this uses a 4069, 2 transistors, 1 mosfet, 1 inductor and 3 zeners of 62 V.

[Max]

Originally Posted by Esteban

Thanks very much, very interesting article! I found a power supply for + B, this uses a 4069, 2 transistors, 1 mosfet, 1 inductor and 3 zeners of 62 V.

So you need stability!

Then why you posted that hartley oscillator that's anything but stable ?

Don't understand these LRLs.... sometimes need stability... other times not... now you talk about tubes... then you wrote about fet amplifiers...

Also LRL related posts are affect by instability !?

Kind regards,
Max

[Esteban]

Originally Posted by Max

So you need stability!

Then why you posted that hartley oscillator that's anything but stable ?

Don't understand these LRLs.... sometimes need stability... other times not... now you talk about tubes... then you wrote about fet amplifiers...

Also LRL related posts are affect by instability !?

Kind regards,
Max

Always you need stability. Tube can be good as receiver for a loop... for example. For the tube I'm not thinking in oscillator. There are many things for to try. As tube is hot inside, maybe is good because molecules inside are most exciting... maybe

[Max]

Originally Posted by Esteban

Always you need stability. Tube can be good as receiver for a loop... for example. For the tube I'm not thinking in oscillator. There are many things for to try. As tube is hot inside, maybe is good because molecules inside are most exciting... maybe

hmmm... no.
The tube is stable cause if you have a regulated current flowing in the filament you have also a very stable temperature inside... no matter of temperature outside of tube, cause there's vacuum inside or some inert very low pressure gas (e.g. argon).

Now, if you have also a stable plate potential you have a perfect amplifier for the purposes you want... very stable.

In semiconductors/bipolar the minority carriers are a huge (if not enormous) pain when also 0.1°C variation is at transistor body... when rest of circuit has very hi amplification.

If you use instead multiple tubes, with voltage gain e.g. 20 you can have enormous gain and very strict thermal induced variations... that's why e.g. old tube based BFOs are SO COOL!

But seem you didn't follow me... oscillator stability is important or not in LRLs ???

Kind regards,
Max

[Clondike Clad]

Originally Posted by Esteban

Always you need stability. Tube can be good as receiver for a loop... for example. For the tube I'm not thinking in oscillator. There are many things for to try. As tube is hot inside, maybe is good because molecules inside are most exciting... maybe

Why not use a mosfet and not a tube???????????????????
Now I KNOW TUBES IN SIDE AND OUT