2020-01-25

Idea Box: Simple Transmitter Circuits w/Ceramic Resonators.

Over the latest year or two I have collected some ceramic filters/resonators for different frequencies.

A simple oscillator (VXO) controlled by a ceramic resonator, either directly on the TX frequency or using a doubler or divider can generate signals in several amateur bands, and here are some ideas for the frequency generation:

Idea Box:
Simple TX for CW (maybe later DSB) for MF and HF bands with ceramic resonators:
- 472kHz: VXO w/480kHz ceramic resonator (472-479 ?) (CW)
- 1.8MHz: VXO w/3686kHz ceramic resonator and divide-by-2 (1800-1840?) (CW)
- 3.5MHz: VXO w/3580kHz ceramic resonator (3500-3575?) (CW)
- 3.6MHz: VXO w/3686kHz ceramic resonator (3600-3680?) (DSB)
- 5.2MHz: VXO w/5500kHz ceramic resonator (5350-5450?) (CW/DSB)
- 7.0MHz: VXO w/7160kHz ceramic resonator (7000?-7150?) (CW/DSB)
- 7.0MHz: VXO w/3580kHz CR and doubler (7000 - 7150?) (CW)(DSB?)
- 10MHz: Super-VXO with 5068kHz crystals
All with PA modules (per band), and a signal derived from the exciter, to a single LCD frequency counter, and, of course CW keying circuit/DSB modulator.
All this could be expanded to a simple TRX with direct conversion RX. RIT control will be needed, especially for the CW mode.

Using a PCB from the Pixie kit could provide some basis for the simple TX circuits, with suitable modifications, e.g. using a ceramic resonator in place of the original crystal, and a simple modification of the low pass filter. This idea comes from VK3YE who made the "Pixie Hack Challenge", providing ideas for different uses of this very low cost kit, with a few additional components, and sometimes removing some components. I think he came up with 12 ideas fo Pixie Hacks, but I do not think he had the transmitter mod. He did, indeed have a hack, using the Pixie as a direct conversion receiver, tuned with a ceramic resonator, but I do not see why that should not work with a TX hack as well.

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