Challenge Thread: The fastest breadboard oscillator on the mudball

[ogden]

More edu, less speculation.

Right. Best way to educate yourself - take breadboard, some transistor and make oscillator of any frequency you can reach.

[AnalogueLove1867]

Hi, a bit late to the party!

Can't believe nobody here hasn't just made a cm or mm long spark-gap bipolar antenna as an oscillator.
Then the capacitance of the bread-board won't even matter.
Spark gaps can go well into the 1 to 100 Ghz microwave zone.
You could even put the miniature antenna into a piece of scap tubing as a wave guide and then measure the radio noise out the other end.
I don't have the equipment for measuring anything beyond 200Mhz so hopefully somebody here can do it instead haha.

ALSO

If you  put a breadboard on top of a sheet of aluminum foil that is directly connected
to the positive terminal of its own power supply an NPN based astable multivibrator will sometimes
 resonate at over 100 times its natural frequency.
Don't know why this happens, and once again hopefully somebody else can try this out with superior equipment.

[buta]

Also attached is a picture is showing the the final version of the tuning network.

zoom_10.JPG

The attached picture zoom_10.JPG shows the tuning network is a motorbike, is it correct?

[KE5FX]

Hi, a bit late to the party!

Can't believe nobody here hasn't just made a cm or mm long spark-gap bipolar antenna as an oscillator.
Then the capacitance of the bread-board won't even matter.
Spark gaps can go well into the 1 to 100 Ghz microwave zone.
You could even put the miniature antenna into a piece of scap tubing as a wave guide and then measure the radio noise out the other end.
I don't have the equipment for measuring anything beyond 200Mhz so hopefully somebody here can do it instead haha.

Extremely small spark gaps are kind of interesting. From that thread:

I tried cutting a slot in the top layer of a copper PCB strip using
a scalpel, the idea being to pinch it shut manually until it fires
somewhere near the bottom of the Paschen curve:

http://www.ke5fx.com/microgap/gap.jpg (closeup)
http://www.ke5fx.com/microgap/10x.jpg (test setup for HV edge)
http://www.ke5fx.com/microgap/50R.jpg (test setup for 50 ohms)

Driving it at -350V through a 100K resistor makes the gap fire somewhat
randomly at about 100 V/ns, limited by the probe and various strays.
The recovery time is also swamped by the scope probe RC:

http://www.ke5fx.com/microgap/mso_10x_probe_1us_div.png
http://www.ke5fx.com/microgap/mso_10x_probe_1ns_div.png

A 50-ohm series tap is faster, but likely still limited by strays:

http://www.ke5fx.com/microgap/mso_50R_1ns_div.png (MSO6054A, 500 MHz BW)
http://www.ke5fx.com/microgap/tds_50R_1ns.gif (TDS 694C, 3000 MHz BW)

I did see some edges closer to .35/3000 = 117 ps, but 164 ps was the
fastest one that I saved before the PCB strip finally broke.