Overmodulation gadget

[WA4WAX]

From the old days.

https://worldradiohistory.com/Archive-All-Amateur/XTAL-for-the-Amateur/XTAL-1949-02.pdf

[K9MB]

From the old days.

https://worldradiohistory.com/Archive-All-Amateur/XTAL-for-the-Amateur/XTAL-1949-02.pdf

I used to like magic eye tubes on equipment
.
My 20A had one.

I like Don Chester’s Over mod sensor.
It uses an 866.
Simple and the blue glow of an 866 is cool!

http://amfone.net/Amforum/index.php?topic=27557.0

[Opcom]

Some very old versions of 866 and 872 have an unshielded filament so that the beautiful flashing glow can be better enjoyed.

If using a standard HV recitifier of any sort, other interesting gas-filled devices can be put in series with the rectifier for a brighter or more unique flash on overmodulation.

The 0A4G octal gas triode tube is one. It usually has a clear top, looks like a fully lit eye tube when on, and is either orange or violet depending on the gas.

A small fluorescent lamp can also be used in series with the HV rectifier. No filament power required by the lamp. A phosphorless one (UV) is hard to find but a regular 4 watt (F4T5) white flourescent tube gives a bright flash that's easily seen.

A voltage bias similar to keep-alive is needed because gas tubes have a 100-150V striking voltage.

Not saying it's efficient but it is pretty and worth a few experiments.