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G4HUP
DFS30 Pages
Simple DFS variants
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The solution recommended by David, G4YTL, for the IC746 is based on Sergei, RW3BP's work. At the moment, this method has not been proven on the IC706, but it will be investigated in the future. If a satisfactory implementation can be found, it will be offered here in addition to the more 'invasive' method described below.
Whilst the prime cause of frequency error at microwaves is the local oscillator for the transverter, the driving rig itself also has a contribution to make. For many applications this contribution is small, and provided the rig is stable, the error will be constant. Where the rig suffers some drift, then this contribution can become significant, especially when digital modes, such as WSJT and JT4x are used. The IC706 is known to suffer from a cyclic frequency shift problem related to the switching of the internal fan.
The above modification reduces the frequency error considerably, but absolute stability can be readily achieved by using an external 10MHz master oscillator, such as a high quality OCXO or GPS disciplined reference source, and DFS30 to replace the internal 30MHz source.
IC706 Modifications Reference locking of the 706 requires that you make an internal connection to the PCB in place of the high stability oscillator option - the instructions given do not provide for any form of switching between the old oscillator (for stand alone operation) and locked operation. This is feasible, but you will need to sort that out for yourself, if you need that. For the rig modification instructions see here |
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