Rubidium drop out of lock with RF?

[VK2GOM]

This is an interesting one... I noticed last night when setting up my IC910H on 2m for WSPR with 50W, that during a Tx cycle, the Rubidium reference locking the rig would drop out of lock.

I wired in my own LED lock/unlock indicators when I originally built it all into a diecast box, so I could keep an eye on its lock status.

The innards of the Rubidium, tripler and filter are completely screened in the diecast box. The input to the radio from the Rubidium box is via coax with SMA's each end.

The only thing not screened is the power supply twinflex cable feeding the Rubidium box.

It only starts to drop out of lock at about 50W RF out or more. Running at 30W it's fine. Antenna is a Yagi, fed with LMR400. Rig is upstairs and has no RF earth.

Any thoughts before I head to Jaycar and buy clip-on ferrite for the power lead? My thoughts are basically what is the process causing it to drop out of lock?

73 - Rob VK2GOM / GW0MOH

[VK2JDS]

Are you running a separate switchmode supply for the rubidium Rob? it could be going low-volts if rf is getting into it. worth measuring the voltage when running 50watts and see if there is any change.
If you are running it from the main dc supply then rf may get in and unlock the pll via that db9 connector.
I have found mine to be stable at carrier levels above 140watts on 23cm and it runs off the same supply the 910 is fed from here.
last night out in the EME hut it was about zero and the RB made a great handwarmer! it just sits on the shelf below the radio and feeds into the xref via sma patch cable. no ferrites.
73 from Dave

[VK3ZTE]

One of the first things I do in situations like this, is to run everything that goes in or out (apart from intended signals) through feed-thru capacitors.

[VK4UH]

I agree with Dave as above.
Try running rubidium from separate PSU from radio as first step

[VK2GOM]

It did indeed turn out to be Volts from the shack PSU drooping below the threshold required for the Rubidium (spec. figure for the Rb is actually 15V!). 12.8V or so was not enough.

Tried it on a separate PSU, and all the problems went away. Thanks all, and to Tim I discussed it with on the phone this morning.

Occam's Razor again!

73 - Rob VK2GOM / GW0MOH

[VK2NR]

I had the same issue with mine Rob. Especially with ssb fluctuations.
It works fine with a dedicated power supply though.
Definitely related to power supply voltage. I spent quite some time determining that RFI was not an issue.

73 - Dave VK2NR.