Challenge Thread: The fastest breadboard oscillator on the mudball

[BreakingOhmsLaw]

Hello everyone, i hope you are having a nice day. To have a little fun, let's start a challenge.
The task is this:

Build an oscillator on a breadboard, using nothing but discrete parts.
The aim is to achieve the highest frequency on the EEVblog forum. The current record holder may call himself the incumbent master oscillator for the time the record is held.
The rules:
1. No ICs (duh!)
2. No crystals / MEMS etc.
3. No soldering except to add wires to SMT parts. All electrical connections between individual parts must be made by the breadboard contacts.
4. The output signal shall be sine(-ish) and able to drive a 10k load at at least 5Volts peak to peak. UPDATE: You may deviate from this rule withitn reason as we have arrived at microwaves.
5. Self-made discrete parts are allowed and encouraged.
6. No cheating. Drilling a hole through your workbench to connect your tracking generator to the underside of the breadboard will be frowned upon.
7. Post an image of your breadboard and counter/scope(Rule 6!) and brief info on the type of oscillator used.
8. Bonus points for nerd value (old/strange/obsolete/abused/haywire parts, exact frequencies, etc.)

EDIT:  of course it is allowed to use common frequency doubling techniques, e.g. distorting and leeching harmonics. Knock yourself out.

Current Incumbent Master Oscillator:
User: joeqsmith @ 25,07 GHz
Incumbent since: May 28th 2020
https://www.eevblog.com/forum/projects/challenge-thread-the-fastest-breadboard-oscillator-on-the-mudball/msg3100558/#msg3100558

Runner-up:
User: PA0PBZ @ 4,77 GHz
https://www.eevblog.com/forum/projects/challenge-thread-the-fastest-breadboard-oscillator-on-the-mudball/msg3100288/#msg3100288
Last update: June 20th



I will kick off with a Colpitts oscillator using a BF256 JFET, tuned to exactly 7,77777MHz by moving my pinky towards the breadboard.



May the best contender win! Go go go!

[RoGeorge]

Great idea!   

I'm in.  Digging through scrap boxes...   

[max_torque]

Hows about a sub section for SLOWEST oscilator as well 

(I'd suggest that for the slow oscilator you need to prove a minimum of 10 waveforms and their frequency needs to be within say 1% of each other to count?

[Jan Audio]

Now lets find out what the best breadboards are, i dont care about the oscillator.

[ArthurDent]

Here's a simple circuit that will generate sine waves into the microwave region although it won't output 10 volts.

[ChristofferB]

I feel like Gunn diodes would also be kinda cheating

[RoGeorge]

I've tried making a DYI tunnel diode like this, but failed so far.   

Some other negative resistance based oscillators there:
http://www.sparkbangbuzz.com/els/zincosc-el.htm

Still tryin'.

Nice blog this site http://www.sparkbangbuzz.com, by the way.

[trophosphere]

I'm thinking about building a PECL ring oscillator built out of transistors fed through a low-pass filter. The wide voltage swing may be a problem.

[ArthurDent]

I feel like Gunn diodes would also be kinda cheating

Like you I had considered a gunn diode but I couldn't figure a good way to mount the cavity on a breadboard or to just eliminate the breadboard altogether. 

[SiliconWizard]

I will kick off with a Colpitts oscillator using a BF256 JFET, tuned to exactly 7,77777MHz by moving my pinky towards the breadboard.

So is the inductor in your Colpitts oscillator only parasitic?

[BreakingOhmsLaw]

No, the big ugly brown thing is a 10uH inductor 😁
80's parts bin FTW!

[SiliconWizard]

No, the big ugly brown thing is a 10uH inductor 😁
80's parts bin FTW!

Oh, right!
Hadn't seen one like this in ages...

[madires]

Don't use low value ceramic caps, use the capacitance of the breadboard.

[BreakingOhmsLaw]

Hows about a sub section for SLOWEST oscilator as well 

(I'd suggest that for the slow oscilator you need to prove a minimum of 10 waveforms and their frequency needs to be within say 1% of each other to count?

I like the idea, but how to prove it? Extra slow roll mode on scope?
Slowest oscillator will win the Galileo award ("And yet it moves!").

[SiliconWizard]

That said, it would be a fun challenge to make a Colpitts oscillator on a breadboard ONLY with parasitic inductance and capacitance from the breadboard itself. Might take a while before you find the right configuration to even make it oscillate.

[ejeffrey]

Does a discrete laser diode count as a ~600 THz oscillator?

[BreakingOhmsLaw]

Does a discrete laser diode count as a ~600 THz oscillator?

I have trouble seeing how you are going to fulfill rule #4:

4. The output signal shall be sine(-ish) and able to drive a 10k load at at least 5Volts peak to peak.

But if you do manage to do that, be sure to give Stockholm a call for your Nobel prize.

[T3sl4co1l]

Did this a whole bunch of years ago on another forum, actually... this is merely to whet your appetite, significantly more is possible of course.



Schematic.  A typical function generator with current mirrors, current-steering diodes, JFET buffer, and schmitt trigger.  Both square and triangle outputs are provided, and more than enough bias is available to power a puny 10k resistor.




Breadboarded.




IIRC, maximum frequency was 33MHz, that must be 10ns/div.  Flat out, no timing capacitor (other than transistor junctions and stray).




With a more responsible, I think 680pF timing capacitor, 4MHz max.  Which would make that 50ns/div.  The ringing is junctions+stray ringing with the cap's lead inductance, which was considerable (~30nH) on account of not bothering to trim the leads.

As it's a VCO, minimum frequency is simply a matter of turning it down all the way; IIRC, it was a chilly evening in the basement lab so the transistor leakage was a few nA, giving a minimum frequency of a few Hz; a dynamic range of 120dB!

Tim

[T3sl4co1l]

Does a discrete laser diode count as a ~600 THz oscillator?

I have trouble seeing how you are going to fulfill rule #4:

4. The output signal shall be sine(-ish) and able to drive a 10k load at at least 5Volts peak to peak.

But if you do manage to do that, be sure to give Stockholm a call for your Nobel prize.

Meh, they wouldn't be too interested, it's more a matter of definition than anything.

I'd imagine one can construct an optical waveguide with dimensions (and indices of refraction) such that, given a reasonable definition of what volts and amperes mean in such an environment, that the voltage magnitude, and the real component of their ratio, are as desired.

It's not something you can exactly poke some probes at, no; but that doesn't mean the concepts are utterly inapplicable.  It's like... making a quantum mechanical definition of classical force; it can be done, it's just not very meaningful, or useful.


As for other ideas, for myself; hmm, I wonder what the most I can do is.  I have some ~3GHz transistors that could oscillate nicely if plugged into a breadboard.  Most of which are SMT, so the plugging might not count, but I have some TO-18s of various types that can very much do the job.

I'm tempted to plug in a vacuum tube, just because I know quite well that I can get a subminiature (wire leads instead of a socket -- particularly breadboardable!) pentode to oscillate ca. 400MHz.  Much more than that, I'm not sure; maybe a UHF triode (6HA5?) in a socket, on leads; don't really have anything hotter than that, though (I don't happen to have any planar triodes, alas).

As for sine waves, best I can do as far as verification is my 1.5GHz spectrum analyzer; if it's oscillating over 1.5GHz, you'd just have to take my word for it that it's not distorting or squegging too badly.


Also if you allow other types of breadboarding besides the solderless socket kind, you may find quite impressive results from some members here (10GHz+ test equipment included ).

Tim

[joeqsmith]

1. No ICs (duh!)
2. No crystals / MEMS etc.
3. No soldering except to add wires to SMT parts. All electrical connections between individual parts must be made by the breadboard contacts.
4. The output signal shall be sine(-ish) and able to drive a 10k load at at least 5Volts peak to peak.
5. Self-made discrete parts are allowed and encouraged.
6. No cheating. Drilling a hole through your workbench to connect your tracking generator to the underside of the breadboard will be frowned upon.
7. Post an image of your breadboard and counter/scope(Rule 6!) and brief info on the type of oscillator used.
8. Bonus points for nerd value (old/strange/obsolete/abused/haywire parts, exact frequencies, etc.)

10k at 5Vp-p seems a bit odd.   Does this mean at DC, you read 10K with your ohm meter?   Don't suppose I could talk you into something a bit more like say 0dBm @ 50ohms?  Can drift and have as much phase noise as we want?   Are there any constraints on the breadboard?  For example, can contact be removed or cut down?   Is there a limit to how much money is spent on it?   

Can we install more than one wire into a hole on the breadboard? 
Thinking about other mods on the breadboard, can we add foil below to tie some of the contact bars together? 

*************************
Bad luck as another knob fell off the LeCroy and I can't seem to find it.   The mechanics of this scope are the worse I have ever seen.  Too bad as it's not a bad scope otherwise.   

With no changes to the breadboard, one hole per wire, all connections on breadboard.   I don't like playing with the higher voltage levels.  50ohms is common for RF and my faster scope is only rated for 4Vpeak max.  For now I am using the 600MHz with the missing knob.  Guessing a cat toy.     

This is my first attempt using a single RF transistor.  Nothing too far out there.  It seems to start just fine.   It's really limited by that stupid breadboard.  Guessing if I pull  out some of the sections and shorten up a few and make some sort of plane,  I could reduce some of this god awful capacitance.   
 
Consider that my entry.

*********************
Small update.  Running it with the 600MHz scope, I assume it greatly attenuates the signal.   The Signal Hound  SA is rated for +20dBm max but I installed a step attenuator and worked my way up.   I had to overdrive the part to get above 0dBm. 

The oscillator is VERY unstable and uses about 50KHz.  That's assuming you don't go near it.   

[tggzzz]

Don't use low value ceramic caps, use the capacitance of the breadboard.

Coupled, literally, with the inductance of the wires.

Here's an example in professional production equipment, a Tek 184. Notice the stirrup with the 1.2-3.5pF tuning capacitor, and the piece of bent wire behind that. It operates at 500MHz.

[TheUnnamedNewbie]

I unfortunately do not have access to my stuff here as I'm in the process of moving and renovating and it is all packed up in a garage, but would second the idea of having it rather be power into 50 ohms or something (and maybe even less than 0dBm?). I personally feel like the requirement of having a large output power limits some really interesting and novel approaches you could make.

[RoGeorge]

Any signal can be amplified or attenuated, so I will consider the rules about amplitude and load resistance as optional.
 

[joeqsmith]

I added a few pictures showing the amplitude of my entry.   I wouldn't mind seeing the load and amplitude requirements drop as well.   The title was fastest, so leave that 10K who knows what outside of DC load for the audio group.   

[Berni]

Interesting challenge there, looking forward to what people come up with.

Maybe i will have a go at it, tho i don't think il get far with just garden verity components from my junk bin.

Are there any extra points for turning it into a radio transmitter? I think you can radiate a fair bit of RF once you get >100MHz along the distances of a breadboard.