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

[Esteban]

Originally Posted by Max

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]

Originally Posted by Esteban

Of course, is important, always!

Then why don't use crystal stabilized one ?

[Esteban]

Originally Posted by Max

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]

Originally Posted by Max

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]

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

[Esteban]

Originally Posted by Clondike Clad

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]

Originally Posted by Fred

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]

Originally Posted by Clondike Clad

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

[Esteban]

Originally Posted by Max

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

I'm planning first stage only by nuvistor tube, because the first stage is the most important. Nuvistor is very small, light, but consumption is like a common tube, filament 6 V. For filament I need batteries appart.

Another candidate is 1S5 tube, because this need in filament only 1.4 V.

[Clondike Clad]

Originally Posted by Max

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

Yes that is true,BUT use for lrl it is a joke.
Keep on it Max you are doing a good job on this LRL site.

[Esteban]

Originally Posted by Clondike Clad

Yes that is true,BUT use for lrl it is a joke.
Keep on it Max you are doing a good job on this LRL site.

Why, if the first electronic LRL made here was with tube (1959) and has not comparisson...

[Clondike Clad]

Originally Posted by Esteban

Why, if the first electronic LRL made here was with tube (1959) and has not comparisson...

Show the circuit and I will build and test it and POST it
If I can't get it to work I will send it to anyone for what it cost me to build it.
From what you are telling us is that unit is as goood as most unit today or better????? .Show us the unit why not let MAX or me build one and test it?IF the tubes unit work LET ME BUILD IT......SHOW THE CIRCUIT ON THIS FORUM...I'LL BUILD IT TEST IT AND POST IT...LET THE JOKE BE ON ME