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Simple DFS variants

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DFSx0 kit

The DFSx0 units are a simplified DFS which gives an output based on odd harmonics of 10MHz only. There are no dividers or mixers involved. In addition to the prime application of transceiver oscillator replacement (DFS30) or SDR transverter LO sources (DFS50), they also make useful system building blocks for other applications, such as:

providing a DDS clock referenced to a 10MHz standard - eg DDS60, see WW2R's system
locking other radios using a 30MHz reference, eg Icom 706 (all marques) IC746 and R75
for mutliplying to higher frequencies - eg double the output of the DFS50 for a 100MHz locked standard.
as a locked LO input for transverters and receive converters for SDR's - with their flexibility we are no longer constrained to traditional IF's of 14 or 28MHz! For example, DFS30 gives 20MHz IF on 6m, and DFS50 gives 20MHz IF on 4m. See also SDR locking page.

Although not specifically kitted, solutions can be provided on this PCB for 70MHz output, and on other PCB's for 90MHz and 110MHz - please enquire!

A new dedicated PCB has been designed for the DFSx0 series of multipliers - for specific version information see the links below:

Download the Technical Manual here. Note this applies to all versions

G4YTL's IC746 solution here.

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

By injection locking the IC706 (or IC746 and R75 models) the option to lock your rig is available to you when needed, but the rig can still be used when the reference source is not available, for example in the car or when portable. In these circumstances it is important to ensure that the DFS30 is disconnected from the rig, otherwise the tuned circuits in the DFS30 will suck signal out of the rig, causing the PLL to go out of lock. When the 10MHz input is provided to the DFS30, this is not an issue.

For the rig modification instructions see here

DFS30 Specifications

Physical

55 x 37 x 30mm tin-plate box (2.2" x 1.45" x 1.2" approx)
Connectors - SMA Female
Construction - surface mount

Performance

Supply Voltage - 10 - 15V DC
Supply Current - 110mA when equipped with input buffer (50mA without)
Input - 10MHz at +10dBm
Output - 30MHz at +5dBm
Spurii - <-65dBc
Harmonics - <-60dBc typ


External view of DFS30 V2	Top view of DFS30 V2


Underside view of DFS30 V2 - output LPF not provided, output attenuator at 0dB	DFS30 output spectrum

Page Created 28.12.09

Page Last Updated 2 Dec 2011