After doing an emotional salute
to the coherer, I got curious to see if any original coherers were available, or a newly made version. No originals, but amazingly Navone Engineering
is making new ones following the original Marconi recipe.
We'll do the unboxing routine. In the box:
The packed innards:
And here's the coherer, along with a penny for scale and a submini tube for comparison. (The powder is in the short gap between the two brass rods.)
The actual coherer looks better up close than Navone's promo pic on Ebay. It's made the same way as the submini tubes that I was playing with
a few years ago.
The enclosed instruction brochure is well written, professionally printed and folded. It runs through the same history I covered, including the Japanese 'second life' of coherers.
Navone included a little piezo sparker to make a proper electric spark. This was actually the hardest part of the experiment for me. I understand coherers but I'd never used a sparker, and various online videos didn't clarify how to use them. The button was too firm for my elderly fingers. I used Channellocks to squeeze it until it SNAPPED, and got a spark.
I set up a simple series circuit on my homemade lab breadboard. After trying various combos of voltage and LEDs and meters and resistors, I ended up using 3V with no inline resistor and a little incandescent bulb.
The coherer is highly sensitive to tapping, as it should be; and it's also highly sensitive to the applied potential difference. When powered by 9 or 18 Volts, it wants to conduct all the time. On 1.5 V it doesn't want to conduct at all. 3V is the Mama Bear.
Very low light before the spark, light increases after the spark, and stays on until tapped.
Here's a GIF showing one sequence of spark on / tap off.
= = = = =
And here's a schematic version.
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Happy second life, Coherers!
Techy footnote: Coherers weren't originally meant to sense nearby sparks and RF in the ether; they were meant to sense RF in the circuit from an antenna input.
They worked both ways.
This real coherer doesn't seem to respond to non-sparky RF. I tried keying my little Pixie 40-meter transmitter
near it, and even touched the antenna wire from the Pixie to the coherer's wire. No brightening. It does
respond to a mechanically generated spark from my flint propane lighter.
Labels: Carver, Equipoise, new toy, Trinity House