Tunnel diode "Interesting" (i.e. useless) experiments

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Post by Ivan on Sat Aug 10, 2019 10:44 am

Hi Harry,
the tunnel diode simply cancels the parasitic resistance of any tuned circuit, including a piece of coax or stripline. Therefore it is really wideband.
Please put your test circuit on your pages ASAP. Thanks.

VBR Ivan

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Post by Admin on Sat Aug 10, 2019 12:36 am

Hi Glenn,
I missed this reply, but i have missed a lot lately. Sorry!!

The heathkit Tunnel Dipper looks really interesting. I notice that the circuit use a TD oscillator (styandard stuff), but then a 3 transistors detector/meter driver. I wonder of the 3.3pf (3.3 μμf) coupling capacitor reactance is the component that determines the frequency "slope"?

It would be interesting to replicate the same technology using modern components.

I once experimented with the old AEY11 and AEY12 TDs (available from Henrys Radio Ltd, 202 Edgeware street London) and I found they would oscillate with ANY coil:

I used a mains transformer primary and had about 800Hz. I relay coil and got 10kHz, a ferrite loopstick antenna from a transistor radio and had 600kHz to 1.8MHz. I even had a bit of coaxial cable oscillating at 1.7MHz and 10MHz, and I still do that today on some of my deeper RF courses. I once used an insulated strip of copper on a copper-clad board and generated 880MHz, and that was picked up on an NMT telephone. It was exactly the same circuit.

The circuit I use today is a bit of block-connector with two crocodile clips so i can couple it to anything. So if you want to know the resonant frequency of an aluminium-foil-clad christmas tree, then this is the thing to use. Perhaps I could make a project of it for HHH? Very Happy

I have a bunch of TDs at home in Sweden, begging for more experimantation. I wonder if I could make a high-gain IF amplifier?

BR Harry - EA/SM0VPO
(Hoping to be QRV tomorrow, Saturday AM @ 11:00 local/SWE/ES time, 10:00 UK time, 09:00 GMT, on 14.200MHz ± 25kHz. Hope there is no contest!!)
(I may be gratefull for some assistance to calibrate my TX and RX frequencies)

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Post by Glenndk on Wed Mar 06, 2019 10:52 pm

Found a tunnel diode use:

Heathkit Assembly manual. HM-10-A Tunnel Dipper (three transistors and a tunnel diode):
https://web.archive.org/web/20190302202148/https://www.vintage-radio.info/download.php%3Fid%3D381

Heathkit HM-10-A Tunnel Dipper:
https://www.radiomuseum.org/r/heath_tunnel_dipper_hm_10_a_hm1.html

Being sold on ebay:
Details about Heathkit HM-10-A Tunnel Dipper with coils:
https://www.ebay.com/itm/Heathkit-HM-10-A-Tunnel-Dipper-with-coils/273736445417

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Post by Admin on Wed Mar 08, 2017 6:07 pm

Hi Glenn,
Thank you for the info. It is always nice to read about perriferal information regarding these things.

BTW, I have found another use for the resistive divider/tunnel diode, I measured the length of 1/2 a drum of RF cable. The TD got the cable to resonate and I just measured the frequency - 1.7MHz. Velocity factor known to be about 0.8, so I had 35 metres on the drum.

BR Harry

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Post by Glenndk on Mon Mar 06, 2017 5:08 pm

Admin wrote:Hello Glenn,
...
I shall have to study the links a bit more, especially the OpAmp circuits. How the h#11 did you manage to find that idea? As I always say, the people on this forum seem to know everything :-) If they don't know it then they find it.

BR Harry

The op-amp can be exchanged for the lambda diode; it just need the resonance circuit to go into chaotic oscillation. You make the transfer function non-linear with the diodes and resistors:
http://www.vk6fh.com/vk6fh/lambda_diode.htm

-

Synchronization of chaos:
https://en.wikipedia.org/wiki/Synchronization_of_chaos
Quote: "...
having two chaotic systems evolving in synchrony might appear surprising. However, synchronization of coupled or driven chaotic oscillators is a phenomenon well established experimentally and reasonably well understood theoretically.
..."


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Post by Admin on Mon Mar 06, 2017 12:54 pm

Hello Glenn,
Now THAT is novel. A chaos generator :-)

I would be interested to see the applications for such a device. I can see a random-number generator application. One cannot help but wonder just what Chua was trying to achieve (like the first person to milk a cow :-)

I shall have to study the links a bit more, especially the OpAmp circuits. How the h#11 did you manage to find that idea? As I always say, the people on this forum seem to know everything :-) If they don't know it then they find it.

BR Harry

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Post by Glenndk on Sun Mar 05, 2017 9:42 pm

How about a chaos oscillator - sinusoidal oscillators are boring and too predictable Smile :
https://commons.wikimedia.org/wiki/File:Chua%27s_circuit_with_Chua_diode.svg
Quote: "...
English: Schematic diagram of Chua's circuit, a simple electronic circuit which exhibits chaotic behavior. Invented by Leon Chua in 1983, it and is very widely used as a standard example of chaotic oscillation. It consists of one inductor (L), two capacitors (C1 and C2), one resistor (R), and a nonlinear negative resistance (NR), called Chua's diode. This device is not a single electronic component but a nonlinear active circuit built using op amps.
..."

https://en.wikipedia.org/wiki/Chua%27s_diode

http://www.cmp.caltech.edu/~mcc/chaos_new/Chua.html
https://en.wikipedia.org/wiki/Chua%27s_circuit

https://en.wikipedia.org/wiki/Chaotic_cryptology

Lissajou curves - go home Smile :
https://en.wikipedia.org/wiki/Lissajous_curve

How about a sinusoidal oscillator modulated by a chaos generator - how does it sound? Or Lissajou curves (two sinusoidal oscillator) modulated by low frequency chaos each.

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Post by Admin on Thu Mar 02, 2017 12:18 am

Hi Ivan and others,
I have difficulty sleeping at the moment, so I did a couple of silly experiments with my Russian Tunnel diode. Perhaps not much serious use, but they could give a bit of food for thought and open up innovative ideas for new projects:

1 - I cut a bit of scrap RG58 coaxial cable to 1/2-wavelength at 145MHz (x VF). Shorted each end with a 1.5cm Dia. loop of wire. I then connected the Tunnel Diode to one loop, and it oscillated very strongly. Cut off the loop at the other end and the frequency shot down to 72.5 MHz. As I clipped off bits of wire I could "prune" the oscillator to any frequency I want. The frequency is surprisingly stable, even when the wire was coilled up.

2 - I have to get rid of stuff that I have no further space for. One of them is a homebrew 145MHz, 4-element Yagi (it had 8 elements but I cannot put it together in this little apartment). It goes in the bin this weekend. Tonight I connected the Tunnel diode inside the coax connector block: the feed point of the Yagi. That, too, began to oscillate immediately, and it was quite strong. Touching the elements, or putting my hand close to them, did move the frequency slightly.

I know that anything with resonance can be made oscillate, and this could open up all manner of project ideas. How about a resonant cavity built into a galvanised dust-bin? Or metal air ducts? I once used a galvanised dustbin as an antenna filter for 28MHz, when a neighbour was running his 27 Mhz CB set "with boots on" (linear amplifier). How about a VFO made with a bit of copper pipe, center resonator rod, and a mechanical piston to control the frequency? Could easily get a frequency range of 10:1 or more Very Happy 

Ok, I am going to try to get some sleep now, but thought I would just put something into writing to share ideas, and also serve as a reminder for this 65-year old brain.

Good night and very best regards to all reading this. Harry - SM0VPO

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