Spark Gap... (smiling) ---- I have a confession.
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While I would love to sit down to a real Spark station-- one right out of the early 1900's, --------adjusting the spark, setting the wavelength,---- trying hard not to get electrocuted--- I have (and this is the confession) ----- Play'd with Spark Gap- as in: On-the-Air type play'd with.
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This was quite a few years ago, in a land far-away---- way outside the bounds of any agency that may have objected. It was during a period of down time on a project-- we had burned out a test radar and where awaiting some replacement parts--- that I and some engineers decided to experiment with "Spark.'
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An idle mind is the Devil's playground.
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It was the combination of a tropical setting, some techno-geek's midnight discussion-turned-to- SparkGap, -- fuel'd by Drambuie, .... all this lead to a-- "Lets try it."
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On our island, the US Navy- the previous occupier, had left a small warehouse full of things to get in truble with.. namely aircraft ignition coils (we won't mention the 25mm aerial distress flares...

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We wired up a transmitter, feeding the primaries with key'd AC. The coil's secondary, with the spark gap, fed a tank circuit dipped to ~1000 Khz-
A secondary coil around the tank fed a Pi network, to giving us a bit of 'filtering' to better notch the 1000 Khz. A long wire, semi vertical antenna, and a longer counterpoise ground completed the setup.
Tune up was easy.... In 'key down,' we tuned for the strongest signal, as received over a portable AM radio. Someone decided to look at the transmitter on a spectrum analy'zr and found our signals suprisingly narrow-- it only wiped out a few hundred Khz's +/- 1000Khz , at a range of a hundred feet.
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"Not bad," we figured.
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Fortified with more Dambuie, and a UHF handheld to report back to 'Base,' the range about the island was explore. Signal strength varied from "590" to "~540" (note the Zero for tonal quality.... but what else is to be expected? this was Spark !) Range; over a one and a half miles.
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A second transmitter was constructed a few days later. This was take by a Zodiac to a nearby island in the atoll, and a "station" was established. Range: now about 3 miles. With portable AM radios for receivers: a QSO (!), between two separate Islands----we were just like Marconi!
More Dambuie!
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No offical callsigns, of course... signal RST's: something like "52-3 by Zero."
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We did it ! ................. QSL cards?... they are still in the mail.
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******Your Tax Dollars, Hard at work******
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On a more serious note;
That's a great photo of the spy transceiver. Majoco, and your family history behind it.

When I look at that radio, I can just imagine being a covert partisan-- hiding in a Paris attic,-- tuning it, hoping to make my contact to the UK...... The Nazi's, all the while DF'ing me .... a death sentence if I'm caught.....
Oh, how I can close my eyes and imagine it! ......Smashing!....

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.............................CF
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Hey, guys, I tried to stay on topic--- this did discuss something MF/LF?
