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DCF77 PCB layouts

8 DCF77 PCB layouts

DCF77 receiver units All described receivers use an RF input stage, though slightly different for large and for small ferrite coils, as well as the ATtiny25 controller plus the ATtiny24 display stage. I have developped a versatile PCB that allows to suit to all the variations that are described here. A PCB with any desired concept can be scissored. All you need is a graphics designer, such as PaintNet or GIMP for example, or, even better and more comfortable, the TGIF vector graphics program for Linux.

All variations fit well on a half Euro-size PCB (100x80 mm), except for the superhet with regulated LC oscillator (120x80 mm), as shown below.

8.1 Modules and connections

Modules and connections This here shows the different modules and their related connections.

8.1.1 The HF-RX module

This module has a size of 20x80 mm. It consists mainly of the FET and the capacitor diodes for frequency adjustment. Two different variations, that differ only in the diode's connections, are here available:
  1. with anti-parallel diodes, e. g. with a KV1235Z and only two diodes used, or a BB212, for larger ferrite coils, or
  2. with parallel diodes, e. g. with the three KV1235Z diodes or three BB112, for smaller ferrite coils.
This module has the following external connections:
  1. the power supply for the whole receiver of +5 V, and
  2. the cross antenna (or any other ferrite coil).
The module has the following in- and outputs:
  1. the operating voltage GND and + 5V to the amplifier/superhet,
  2. the two symmetric RF outputs HF+ and HF-,
  3. the AFC input for adjusting the frequency.

8.1.2 The Direct-Receiver modules

The two modules for directly receiving DCF77 with transistors or the one with the TCA440's IF amplifier are both of a size of 30x80 mm. The following connections are available:

8.1.3 The Superhet receiver modules

(These modules are still under construction.)

8.1.4 The AM rectifier modules

The two alternative rectifier modules, either with diodes or with an ATtiny25 controller, rectify the RF or IF and hand the result over to the controller/display module. The operating voltage for that stage stems from the Amplifier/Superhet stage.

8.1.5 The Control- and Display-module

This module is identical for all receiver variations. The controller ATtiny25 measures the voltage that comes from the rectifier, and generates (via PWM plus RC filter) the AGC- and the AFC-voltages. The AFC voltage line crosses the amplifier/superhet module to get to the RF-RX stage. The DCF77 results are transmitted via the internal Two-Wire-Interface to the ATtiny24, which displays the results on the connected LCD.

This module has additionally an ISP6 interface connector. This can supply the operating voltage from an attached ISP programming adapter, if the programming adapter provides 5 Volt. If one of the three controllers shall be flashed, the programming pins RESET, MOSI, MISO and SCK can be temporarily attached to the ISP6 plugs using enameled wires.

8.2 Links to the PCB layouts

The following parts are incomplete because not all layouts are complete.

To download the files place the mouse over the entry and, in the context menu, select "Save linked file as ...".

8.2.1 Layouts for the modules

The PCB layouts of the modules are available here as gif graphics files, e. g. for the RF-RX part those look like:

PCB layout for the RF-RX anti-parallel

The associated component placement plan looks like this:

Component plan for RF-RX anti-parallel

ModuleSizeVariation PCB layoutComponent placement plan
HF-RX20x80Anti-parallel HF-RX-A HF-RX-A HF-RX-A HF-RX-A
Direct receiver30x80with Transistors Trans Trans Trans Trans
with TCA440 TCA440 TCA440 TCA440 TCA440
Superhet30x80with internal LC-oscillator SuperLC SuperLC SuperLC SuperLC
with divided XTAL SuperXT SuperXT SuperXT SuperXT
50x80with regulated LC-oscillator SuperRegLC SuperRegLC SuperRegLC SuperRegLC
AM rectifier50x23with diodes Diodes Diodes Diodes Diodes
with ATtiny25 Rect25 Rect25 Rect25 Rect25
Control-tn25/Display-tn2450x57 CtrlDisp CtrlDisp CtrlDisp CtrlDisp

8.2.2 Complete PCB layouts with combinations

All PCBs are 50x80 mm (half Euro-Format).

Here for example is the combination of HF-RX-a, TCA440-Direct receiver, ATtiny25-Rectifier and ATtiny25-Controller/ATtiny24-Display on one single PCB. Layout and component placement are downsized (the originals below are double that size;!)

TCA440-Direct receiver Component plan TCA440-Direct receiver

HF-RXDirect receiver Superhet with oscillator optionRectifier tn25-Controller
PCB layoutComponent placements
Anti-parallelParallelTransistors TCA440Internal LC XTAL with DividerRegulated LCDiodesATtiny25 as giffor tgifas giffor tgif
Direct Transistor XX X X Trans Trans Trans Trans
Direct TCA440X X XX TCA440 TCA440 TCA440 TCA440
Super-LCX X XX SuperLC SuperLC SuperLC SuperLC
Super-XTAL X X XX SuperXT SuperXT SuperXT SuperXT
Super-LCtn25X X XX SuperRegLC SuperRegLC SuperRegLC SuperRegLC

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