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Written by Axel Eng September 1998 Updated March 2001 (C7 was wrong on the 5W board) - thanks to Syst3m. December 2001 note: I no longer checks my e-mail regularly and can't promise replies to questions. If you're unsure about anything, try asking in the Usenet group alt.radio.pirate. - Axel |
Parts Assembly Power supply Antennas Tuning The 5W version Assembly Kits |
Fig 1: Wiring diagram for the 1W Veronica
The TX has a built-in "mini-mixer" which makes it possible to use it without any external mixing table. This consists of the transistor T1, which amplify the mike signal before it gets combined with the CD (or tape) one. R1 and 2 are adjustable resistors (potentiometers) which is used to set the audio level (see the tuning section).
The components between R8 and C21 is the oscillator, the part which generates the radio signal. The diode D1 is a so-called "varicap", which can be seen as an variable capacitor, controlled by the audio signal. That, C12, 13, and the coil L1 decides the frequency. The oscillator is actually two oscillators, operating in antiphase around 50MHz. When the two signals are combined, they make a 100MHz signal. This setup is generally much more stable than one oscillator operating directly at 100MHz. The signal is then amplified up to 1W in T4.
To the far right is a the tuning aid, which rectifies a part of the output and controls the LED D5. The higher output, the brighter is D5.
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Fig 7: The output stage of Veronica 5W. Everything to the left of T4 is identical to the 1W one.
^ The 5W version
The 5W version of the Veronica is pretty similar to the 1W one, but with an extra amplifier stage (T6). As mentioned, the MRF 237 transistor costs around $20, and should be handled accordingly.
^ Parts list
Parts not mentioned are identical to the 1W version.
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Fig 10: PCB placement of the Veronica 5W
If you're unable to make a PCB or can't get all the parts, it's possible to order these transmitters in kit form. You can either order them directly from the manufacturers in England (Veronica Kits or from US companies like LD Brewer. The 1W one costs £30, while the 5W one costs £60. Be ware that these kits are a bit different from shown here, they don't have the mike amp, nor do they have space for a voltage stabilizer.