SSB Exciter with IF-Clipper for QRP.

DL6ZB, Rolf Heine

SSB Exciter

This is a description of a simple but effective single side band exciter for 10.7 MHz with a built-in if-clipper. This conecpt is suitable for other IF frequencies, too (e.g. 8/9 MHz) by changing the crystals.

I developed a special 50 ohms SSB (USB/LSB) crystal filter for this exciter in a so-called bridge design. This filters are more suitable for SSB generation for me than ladder filters since bridged filters can be tuned very easy without significant change of impedance. Just change the 33pF capacitors to change the bandwidth of the filters. This filters can also be used for if-stages of receivers. Just cascade it for higher filter orders. The bandwidth depends on the capacitors (see C1/C2) only. The greater the value the narrower the bandwidth. This filters can be tuned from 6000 downto 300 Hz bandwidth within a 2.5:1 VSWR bandwidth (50 ohms). The sideband is changed by tuning the carrier oscillator crystal. The crystals needn't be selected or matched, although I recommend to use crystals from the same type (manufacturer).

The switchable built-in IF-clipper is a well-known simple but effective diode clipper made from germanium diodes and a step-up transformer. It was first described by Wes Hayward, W7ZOI. Following the IF-clipper is a second crystal filter for a clean SSB output signal. A clipper theoretically offers a +6 dB increase of readability. This could be a great helper for QRP. I use this exciter in my 160/80/40m QRP-SSB transceiver with good results.

The "SSB EXCITER 10,7.brd" is an Eagle CAD file. A free (limited) version of the Eagle PCB layout software is available vom CADSOFT on the internet. Look for the free version.

The bottom layer is the routed one, while the top layer is used as ground only. This is a single layer PCB, although the PCB is double sided copper.

Try this link for the CAD software:
http://www.cadsoftusa.com/
Click here for the 10.7 MHz SSB Exciter PCB layout file


Circuit Diagram:
Click on picture for a large scale view

Circuit Diagram SSB Exciter 10.7 MHz



Place plan:
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SSB Exciter Place Plan


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