I have used the indicator neon tubes (the sort used in sockets and switches that are a bit smaller than a baked bean) as RF detectors of very short pulses- biassed just below ignition (about 70-80V from memory) the additional pulse  energy tips them into conduction, and then an avalanche of ionisation means it stays lit until the supply drops away. By suitable choice of RC time constant one can make  'pulse stretcher', that turns any very short duration  RF signal of any frequency over a very wide range  into a burst of DC, that can be counted - rather like the clicks in a Geiger counter. A radio EMP counter if you like.

In terms of radio reception its more deaf than a crystal set, and totally untuned, but the qualities of 'responds to anything large enough ' and 'not destroyed by overload' are both sometimes useful.

The easy strike ones have radionuncleides in to give them a bit of a head start - but they don't make such good detectors.

By the time they are flickering the ignition voltage has risen by a mix of gas loss and electrode evaporation, and presumably it is very sensitive to the odd volt more or less, far more than a normal appliance.

You may find nothing wrong, other than both the mercury vapour in the florry and the neon in the indicator  are as it were on the way out - both will become very voltage sensitive, just before giving up the ghost altogether - at that point spikes on the mains or a volt or two of RF may well be the difference between strike no strike and affect both.

And yes, they are also light sensitive - for RF detector use they needed to be blacked out.

Mike.

PS the earlier  tubes the underground used to be DC -  and now we really show our age - that was the era of wooden escalators and mostly smoking carriages and the odd non-smoker, or from the mid 1970s, replaced by transistor inverter designs  running at a few KHz, and by then mostly non smoking carriages and the odd smoker.

The DC ones used to leave the tube dark at one end, and the inverter ones use to get a pretty stripes effect that moved a bit as the transistor bias changed and the frequency of the inverter wandered. Given it was all based on a traction voltage of 660 or so, that was soemrthing more like 500 on the train when accelerating and drawing peak current, and more like 800 plus when braking hard and regenerating back into the rails, precise stability was not really a feature.

All led lights with regulation now I think.

Mike.
 

I have used the indicator neon tubes (the sort used in sockets and switches that are a bit smaller than a baked bean) as RF detectors of very short pulses- biassed just below ignition (about 70-80V from memory) the additional pulse  energy tips them into conduction, and then an avalanche of ionisation means it stays lit until the supply drops away. By suitable choice of RC time constant one can make  'pulse stretcher', that turns any very short duration  RF signal of any frequency over a very wide range  into a burst of DC, that can be counted - rather like the clicks in a Geiger counter. A radio EMP counter if you like.

In terms of radio reception its more deaf than a crystal set, and totally untuned, but the qualities of 'responds to anything large enough ' and 'not destroyed by overload' are both sometimes useful.

The easy strike ones have radionuncleides in to give them a bit of a head start - but they don't make such good detectors.

By the time they are flickering the ignition voltage has risen by a mix of gas loss and electrode evaporation, and presumably it is very sensitive to the odd volt more or less, far more than a normal appliance.

You may find nothing wrong, other than both the mercury vapour in the florry and the neon in the indicator  are as it were on the way out - both will become very voltage sensitive, just before giving up the ghost altogether - at that point spikes on the mains or a volt or two of RF may well be the difference between strike no strike and affect both.

And yes, they are also light sensitive - for RF detector use they needed to be blacked out.

Mike.

PS the earlier  tubes the underground used to be DC -  and now we really show our age - that was the era of wooden escalators and mostly smoking carriages and the odd non-smoker, or from the mid 1970s, replaced by transistor inverter designs  running at a few KHz, and by then mostly non smoking carriages and the odd smoker.

The DC ones used to leave the tube dark at one end, and the inverter ones use to get a pretty stripes effect that moved a bit as the transistor bias changed and the frequency of the inverter wandered. Given it was all based on a traction voltage of 660 or so, that was soemrthing more like 500 on the train when accelerating and drawing peak current, and more like 800 plus when braking hard and regenerating back into the rails, precise stability was not really a feature.

All led lights with regulation now I think.

Mike.