HW-101 Direct Digital Synthesis Project
Why DDS For The Old Rig?
The old HW-101 had worked a lot of DX and had served us well. Its electronics were actually in fair shape but the old VFO gears and bearing had worn to the extent that it did not tune smoothly and would jump a few hundred Hertz on its own. Therefore it had not been used in several years. N4YG hates things that do not work properly and decided to take the DDS approach. The Analog Devices 9835 DDS chip was selected because it satisfied all the requirements for a local oscillator tuning from 5.500 MHz to 5.000 MHz (Yes, it tunes backward).
The project was very successful. A forum presentation was made on the project at the 2005 Huntsville Hamfest. Click on the link above to see the slides from the presentation.
An Updated Design With PC Board
The first three photos are of the initial design and hardware. The last three photos are of an updated design using a PC board. It includes several features not in the previous design. The amplifier has been improved and its output level is now variable and should be sufficient for even the highest drive levels. An optical band sensor is included but cannot be seen in the photograph. It is beneath the chassis and is designed so that it can be installed without any disassembly. The sensor encircles the band switch shaft, yet it does not touch or interfere or in anyway change the operation of the band switch. With this band sensor, the frequency displays the correct frequency at all times and it allows specific calibration to be applied for the current band. Not also that the 6AU6 output stage has been moved to the right side of the chassis, making the area neater and more accessible.
Printed circuit boards are now available. These boards are fully assembled, tested, and complete with connectors and cables. Contact N4YG for more information.
It Works In The Drake TR7/RV7! How About Your Old Rig?
AD3G, Paul, has installed the board in the RV7 (see photo below), the remote VFO for his Drake TR7. Perhaps the DDS board can be used to improve the operation of your old rig.
