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Another Tiny Transmitter




 
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February 20, 2019, 03:27:55 PM *
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Author Topic: Another Tiny Transmitter  (Read 393 times)
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WA4WAX
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« on: February 01, 2019, 09:41:01 PM »

About 1 watt.  CW only, but I guess one could mod it.  Got a couple of 1S4's??

* PW-1955-03 [68].pdf (3999.08 KB - downloaded 103 times.)
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ka1tdq
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« Reply #1 on: February 03, 2019, 03:59:50 AM »

At 1 watt, maybe just screaming at the B+ supply would do it.

Jon
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #2 on: February 03, 2019, 08:58:02 AM »

Or no tubes at all and talking in a carbon mike in the ground of the antenna system
1912, Moretti Spark gap, Marzi carbon microphone, 1 kW AM!!!!
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #3 on: February 03, 2019, 08:59:44 AM »

forgot the pic.

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kb3ouk
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« Reply #4 on: February 03, 2019, 10:12:29 AM »

If it could handle the voltage, you could almost put the carbon mic in series with the B+, it is only 90 volts and the battery voltage on a telephone line is typically 45 volts or so, so it might work. The variable resistance of the carbon mic under audio would vary the plate voltage, which would modulate the transmitter.
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #5 on: February 03, 2019, 10:40:14 AM »

The Marzi microphone is a complex construction that can handle a few amps of RF using a stream of carbon powder to avoid heating. In the old days of AM, it was common to put a carbon mike in the antenna system to modulate. In order to handle high currents, many microphones were used in series or parallel, see the Lorenz microphone
In the B+ line it will not modulate well, the impedance is too low. But I did put a circuit for a carbon mike substitute in the Military section. When using a bigger transistor and more current, you can directly modulate the transmitter with an AF output transformer in reverse.


* Moretti sparkgap.jpg (36.79 KB, 424x324 - viewed 21 times.)

* Marzi microphone principle.jpg (24.34 KB, 293x419 - viewed 20 times.)

* Lorenz microphone.jpg (36.92 KB, 365x376 - viewed 20 times.)
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Patrick J. / KD5OEI
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« Reply #6 on: February 03, 2019, 01:01:45 PM »

Back in the day I can imagine them employing a small boy for a few pennies a day to stand there and empty that cup of carbon back into the hopper while the thing was live.   Tongue
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