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]

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/Nuvistor/nuvistor.htm

There are some example circuits that might be useful.

[Esteban]

Have a look here ->

http://www.thevalvepage.com/valvetek/Nuvistor/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]

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]

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]

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

[Esteban]

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

Of course, is important, always!

[Max]

Of course, is important, always!

Then why don't use crystal stabilized one ?

[Esteban]

Then why don't use crystal stabilized one ?

In off-resonance for pistol, you need an oscillator in wich the coil be an important part of the oscillator, in other "prefabricated" oscillator you don't see important changes. In the oscillator I post, minute variations can be amplified, but you can't move strongly the pistol.

[Esteban]

I'm planning for the nuvistor a no-oscillator type pistol.

[Fred]

no matter of temperature outside of tube, cause there's vacuum inside or some inert very low pressure gas (e.g. argon).

I never thought about that...the neutral gas making thermal isolation.
cool
regards,
Fred.

[Clondike Clad]

tube??????????????????

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

[Esteban]

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

Fet... mosfet... yes I try it. I remember also you suggest to use tube.

Here only one tube, input, the others are common semiconductor.

[Max]

I never thought about that...the neutral gas making thermal isolation.
cool
regards,
Fred.

Not cause it's inert chemically ...but cause of very low pressure... yes it is... cause density isn't enough for good thermal exchange...

Indeed, some so-called "vacuum-tubes" are not in hi vacuum but with small pressure of inert gases... like argon.

An example is thyratron but some e.g. voltage regulators uses neon or gas mixtures at different pressures, depending e.g. on current they must carry.

Usually vacuum tubes are fairly the best choice for stability in tube oscillators but special kind filled with few inert gas (at very few pressure) or mercury vapours are suitable and even more stable cause of internal design. Many of them (also very small size for portable devices) were made by Raytheon.

Kind regards,
Max

[Max]

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

Welll... I must say that in some applications tubes are fairly better still today.
The problem is that semiconductors technology never really solved that issue of stability...

As an example... I made many years ago an oscillator for MD using common fets... I made everything absolutely by the book... considered controlling the current and making feedbacks , but , at the end, I tested the oscillator under various conditions and found that was absolutely instable vs temperature, no matter compensation strategies I tested (many).

I've then redesigned using small tubes , 6.3V powered and got perfect , stable sinus , no matter if I also swing an hairdryer near the osc module...
The MD was rock steady, then I learnt that for some stuff... better using old tubes than newer stuff.

About stability, experience say me that mosfets are good... but tubes are BETTER.

Kind regards,
Max