Reference locking the IC-7400/IC-746pro

[VK2XAX]

Hi all,

I recently completed a project to reference lock my Ic-7400. This rig is easier to do since you can use injection locking to bring it on frequency. This involves coupling a reference signal into the LO.

To do this I wound 5 turns of 0.3mm wire around L1901 in the LO circuit and brought that out to the back of the rig via tiny coax to an SMA. I didn't want to drill holes in this rig so I mounted the SMA to a plate that was then bolted to a convenient spot on the back panel vents. I selected a place that was out of the main air flow from the PA so as not to compromise cooling.

The IC-7400 uses a 30.2Mhz LO so I once again turned to my favorite Rubidium Oscillator, the FE-5680A revision B.

The RB's DDS I reprogrammed to 10.666666Mhz, built one of my low noise tripplers, added a small SMP buck booster to isolate everything from PSU fluctuations and filtered that will an LT1764 low noise regulator.

The result.... a signal with a phase noise of -101.3dBc/Hz @ 1khz and within 0.037 Hz of the required 32Mhz and harmonics >65Db down on the fundamental.

The 7400 is now rock steady with excellent phase noise and no increase in harmonics. Mind you the IC-7400 already has excellent phase noise performance so basically this addition did not detract from that but added frequency accuracy and stability.


regards

Tim

[VK2ZRH]

That's what I like to see - a bit of discipline

Well done, Tim.

73, Roger Harrison VK2ZRH

[VK2XAX]

LOL.... very funny Roger

Also here is a few more pics of the back panel....

[VK2GOM]

Good stuff Tim.

I'm sure the major manufacturers will slowly introduce 10MHz ref in sockets on commercial radios, now that stability is a requirement for data modes.

And Roger, that's the exact same method by which your 746 is locked (only, of course, with GPS).

73 - Rob VK2GOM / GW0MOH

[VK2ZRH]

Hi Rob,

Yes Rob, I'm aware of how my '746 is locked

I'm working on putting together a distribution amp system for the Trimble reference in my shack-to-be, to "discipline" other items of equipment.

Given that hams have been ref-locking their rigs (or attempting same) for the past decade, I'm sure the manufacturers will surprise us some time soon by including it as a BIG DEAL FEATURE

I like your make-no-holes approach, Tim.

73, Roger Harrison VK2ZRH