NDR oscillators - has anyone experimented with them?

Hi Glenn,
Yes, it should be quite possible to use a lambda diode transmitter, as an exciter for a higher power device. My main interest in inthe QRP side of things, but as you pointed out, an IRF510 should still be able to give a respectable output power.

A lot of food for thought, and this must be one of the most interesting threads I have had on the forum. Nice that there are so many knowledgeable people still on the forum.

Very best regards from Harry Lythall - SM0VPO

Admin wrote:
Perhaps the lambda diode can be used in the two TD transmitter and get several milli-watts out?

With Franks/vk6fh circuit and Ruuds link, it should be possible to make a power lambda-diode based HF power amplifier/transmitter consisting of a power (LD)MOSfet ( https://en.wikipedia.org/wiki/LDMOS ) (an IRF510 or STP16NF06 ?) or a tube e.g. EL519 - and a common HF PNP power transistors (n*BD140) - or a p-channel power (LD)MOSfet (an IRF9510)? :-)

Instead of inductor transformers/tapping, a capacitive divider transformer could be used to control the coupling/matching between the (power) lambda-diode and the resonance tank circuit. "Reviving" the simple inductor again. Then Q-lowering extra series resistors (R5) and parallel resistors could be history. The parallel lambda-diode capacitor could also be variable (varactor diode?):

See (last) right illustration:
http://www.circuitstoday.com/wp-content/uploads/2009/10/tunnel-diode-oscillator-circuit.jpg
(from http://www.circuitstoday.com/negative-resistance-oscillators )

Quote: "The Colpitts Oscillator design uses two centre-tapped capacitors in series with a parallel inductor to form its resonance tank circuit":
http://www.electronics-tutorials.ws/oscillator/colpitts.html

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The coupling/matching between the two "LC"-tanks could also be implemented by more (shared) capacitive dividers.

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Could somebody please analyze the fet-fet and fet-transistor lambda-diode of Miller-capacitor-amplification ? (I do not see any)

Hi Ruud,
That is an interesting project. Two tunnel diodes; one as MO and the other as a PA 
It is interesting what you can do with these tunnel diodes.

Hi Glenn
Thank you very much for the link to Frank's using the lambda diode.

@ both
The lambda diode has several volts operating range at a fair few mA, whereas the TD only has a few V. Perhaps the lambda diode can be used in the two TD transmitter and get several milli-watts out? Hmmm... Bit of food for thought. I can see that I am going to have a lot of fun in my semi-retirement. All I need to do is to build up the workshop so I have some equipment to experiment with, then ... who knows 

This evening I hope to update the homepages with a new project. As stated earlier, my GDO is a bit long in the tooth, the dial is unreadable and it does look a bit crappy. I sometimes feel a bit embarrassed when I project it on the 6-metre wide screen for 60 people at a time. This weekend I couldn't sleep so I built a new one with a HUGE meter. I had thought about using the Lambda diode as the prime component, but I decided on simplicity.

Thank you both very much for all your input. Really appreciated. Perhaps it is now time to consolidate all these links into a single post?

Very best regards from Harry - SM0VPO

(PS - I rarely delete old contacts from my address book. Last night I had an accident in LinkedIn and I think I managed to send a connection request to everyone in my Windoze address book. So if you received a connection request, please remember that LinkedIn is not my prime social media. I do read it from time to time.)


(PPS - I see I have managed to send myself a LinkedIn connection request to me!)

Fascinating components, those tunnel diodes!
On the internet I found a design of a 'tunneldiode transmitter'.

(Here is the link: in Dutch... http://www.pi4raz.nl/index.php?option=com_content&task=view&id=3523&Itemid=46)

Frank has a newer version of a GDO (LDO?) on his page here:

Negative resistance and the lambda diode:
http://www.vk6fh.com/vk6fh/lambda_diode.htm
Quote: "...
The advantage of this type of oscillator is that two-terminal (i.e. no taps) inductance coils are all thats needed!
Since P-channel JFETS have a relativley shallow transfer curve, a bipolar transistor can be used in its place.
...
The "Lambda-diode" so formed is biased to the negative resistance region by means of P1 .
Experimentation would suggest that point is about 4 volt.
...
With the wiper of P1 most +ve oscillator is inoperative and meter reading will be at a minimum.
...
Therefore advance P1 wiper till deflection just increases (oscillator is now running).
...
REFERENCES:

Wireless World: Jan & Feb 1957 M G Scroggie (Cathoderay)
NEGATIVE RESISTANCE - MYSTERY OF THE BACKWARD BENDING CURVE

Elektor magazine October 1979. A modern grid-dip meter page 10-22

Amateur Radio (Australia) January 1997 A dip meter using the Lambda diode page15
..."

Wireless World: Jan & Feb 1957 M G Scroggie (Cathoderay)
NEGATIVE RESISTANCE - MYSTERY OF THE BACKWARD BENDING CURVE:
http://www.vk6fh.com/vk6fh/negresistance1.htm

Hello again Glenn,
Thank you very much for the link. After I received a message from Ramon Vargas that his lambda diode was on my homepages, I started checking my site. I must admit that I have neglected the Visitors section for quite a while (no new visitors projects offered) so I had forgotten most of the projects there.

Thank you very much for the link. I can see that I will have to update or re-organise that section of the homepages. I must also re-familiarise myself with it 

At the moment I am re-doing my GDO circuit, because my trusty old GDO is more than 35 years old. I rely heavily on it when I give my courses (40 - 60 participants in one sitting). I have nearly finished the replacement, but I may try a new circuit using the lambda diode.
BR Harry - SM0VPO

(PS: http://213.114.137.49/ is my little RaspberryPI)

I also found this:
http://213.114.137.49/_visitors/blocks/lambda_diode.htm

Another interesting little snippet of info,

The article by Ramon Vargas-Patron on lambda diodes was supplied to me 10 years ago to put on my homepages, visitors section. I had forgotten all about it!
The article is located at:

http://213.114.137.49/_visitors/tech/oscillationsandregenerativeamplificationusingnegativeresistancedevices.pdf

I guess I should go through ALL my homepages from time to time. Kinda difficult to remember everything that is on there.

BR Harry

Hi Glenn,
That is a very interesting article - a mixture of bipolar and FET.
You have been a lot more successful at finding information on the web than I have been. I thank you very much for all your help.
Now i have to do some reading and a lot of experimenting 
Very best regards from Harry

Found an interesting modified lambda-diode:

Oscillations and Regenerative Amplification using Negative Resistance:
http://www.zen22142.zen.co.uk/Theory/neg_resistance/negres.htm
"...
The author also tested a modified version of the Lambda diode in which a 2N3906 PNP silicon bipolar transistor substituted for the P-channel JFET.
...
Fig.8 Regenerative receiver for the MW AM broadcast band
..."

(from: https://sv.wikipedia.org/wiki/Negativ_resistans )

Hello Glenn,
Thank you very much, I just spend 15 minutes writing a reply but somehow lost it.

> https://da.wikipedia.org/wiki/Negativ_differentiel_modstand
That is an interesting article. Also rather surprised that I can read it without any problems. Jag kan Svenska men har aldrigt försökt att läsa Norska (eller är det Danska?) 
That opens up a few doors for me.

The neon oscillator I first used in about 1969 when I made my first oscilloscope. The neon was used to generate the timebase and directly applied to the horisontal deflection plates. An ECC81 (12AT7) was used for the X-axis deflection plates. I saw in the norwegian page that the "glimmerlampe" from flourescent tube starters work in the same way. I have also used the neons from these mains tester screwdrivers, but when I was a kid we could buy them for next to nothing for panel lamps.

But the link http://users.tpg.com.au/users/ldbutler/NegResDipMeter.htm was perhaps the most interesting. That is the information I have desperately seeking on the web. I saw an article about 25 years ago, which I am sure documented the same negative resistance effect using two FETs.

Thank you very much for the information. I am really grateful for the links and they will make a lot of interesting reading for me over the coming weekend.

As regards the galvanised items, I was more than a little surprised, but I have recently seen a cable installed after the installer had eaten lunch. His fingers contaminated the RF connector and the corrosion created a heap of inter-modulation. It wiped out all communications between a radio base station and an LTE mobile telephone (hard wired, not over the air). It created about -90dBc inter-modulation (-50dBm at the RBS receiver input). So there were about 1200 LTE carriers all mixing with each-other 

I have a BC547 negistor on the bench at the moment. It works in an audio oscillator, and can make a 500kHz crystal hoot. But it didn't work with a 7MHz tuned circuit. Thanks to good information from Ivan I am now waiting for a few Tunnel Diodes so I can do some work on VHF oscillators. When I was a kid I spent a lot of pocket money on AEY11 TDs from Henry's radio (202 Edgeware road, London) and built loads of experiments, including audio and 100MHz oscillators. That was also my first wireless microphone.

Thank you very much for the information. Although there are so few people using the forum after such long inactivity, I am grateful for all the information I have gleaned over the past few weeks. You, Ruud and Ivan are fantastically active and a goldmine of information and assistance.

thank you very much, from Harry - SM0VPO (JO89WO)

I have also been fascinated about negative differential resistance. (and many other things...)

Please look at the references in:
https://da.wikipedia.org/wiki/Negativ_differentiel_modstand

E.g.:

Video: Neon light oscillator circuit:
https://www.youtube.com/watch?v=7S1PHy6BZqA

Everything with plasma has a Negative Resistance region, unless the electrodes are to lossy...

Negative Resistance Revived. by Lloyd Butler VK5BR. (Condensed version of article originally published in Amateur Radio, November 1995):
http://users.tpg.com.au/users/ldbutler/NegativeResistance.htm

A Dip Meter Using the Lambda Negative Resistance Circuit.
by Lloyd Butler VK5BR
(Originally published in Amateur Radio, January 1997)
(Correction made in Sept. 2007 - see note):
http://users.tpg.com.au/users/ldbutler/NegResDipMeter.htm
I think there is missing a 1nF over D3.
http://www.keelynet.com/zpe/lambda3.jpg

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A Negative Differential Resistance Oscillator with a Negistor:
http://jlnlabs.online.fr/cnr/negosc.htm
"...This NDR component is a common and cheap NPN transistor 2N2222A..."

The Negistor & Negative Resistance - 04/07/00
courtesy Marcelo Puhl:
http://www.keelynet.com/zpe/negistor.htm

(#0093) World's Simplest Single Transistor Oscillator - BJT with Negative Resistance:
https://www.youtube.com/watch?v=rpGOKGrcpAk

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The best are here :-) :

Negative Resistance Oscillator with Homemade Tunnel Diode.
By Nyle Steiner K7NS May 9. 2002
Updated March 2003:
http://www.sparkbangbuzz.com/els/ntype-nr-el.htm
( Cool Homemade Stuff etc.: http://www.sparkbangbuzz.com/ "Zinc Negative Resistance Oscillator.", "Zinc Negative Resistance Crystal Oscillators and Zinc 80 Meter CW Transmitter.")

Now you can never pass a bunch of nuts and other galvanized items, without thinking how much electronics you could have made with it :-)

Actually it get much better :-)

Homemade Vacuum Tube Triode:
http://www.sparkbangbuzz.com/els/hm-triode-el.htm

thank you very much Ivan.
Now all is clear. I thought I was missing a bit of basic knowledge 

Thank you also for the datasheet, I really appreciate it. Now I will be able to do a bit of playing when I get them.

VBR Harry

Hi Harry and all,
NOS = New Old Stock = parts and devices, which have been stored for long, but never used. Often the come from military surplus.

BR from Ivan

Hi Ivan, thank you for the response.
By the way, what is "NOS"?

BR Harry

Hi Harry,
there are tunnel diodes on eBay. Most of them are Russian NOS GaAs switching types, often offered in 5 or 10 pcs lots, beginning at 5 USD/lot. I expect they may be forced to work as oscillators, too.

BR from Ivan

Hello all,
At the moment I have several projects on the drawing board:
1 - UV light box (my old one is in Spain)
2 - Re-building my GDO (the old one is a bit old in the tooth)
3 - Simple oscillator

For #3 I had thought about using a Tunnel Diode, such as the 1N3149 or 1N3149A. unfortunately I cannot find a source of TD's at a reasonable price, and even then only 1-off.

I remember once reading that a 2N2222 transistor can have 12V fed between Collector and Emitter (+ve to the emitter) via a 1K0 resistor. It draws a few mA and varying the voltage causes the current to rise when the voltage is reduced = negative resistance. I have a BC547 on the bench at the moment and that seems to do exactly the same.

Has anyone had any experience in this field? Maximum frequency? Is it consistent for any particular device?

I am about to give this a try and I will post any results I have to offer.

Very best regards from Harry