WWVB antenna interferance from AC/DC converter supply

Question

I'm working on a design that uses a WWVB antenna receiver....

The WWVB antenna is a small (~ 1/4" x 4" rod). Size is not a constraint so I could make it much bigger if a I half to.

The design is powered by AC/DC converter w/ SMPS. Its an unenclosed module I got off digikey. Whenever the Supply is on and near by the antenna receiver cannot pick up a signal.

The antenna & Powersupply have to be able to operate together in a small enclosure. How can a shield the Antenna from the noise?

Design a receiver that has better filter?

Use ferrite RF shielding sheets?

Design a larger antenna?

Position the Powersupply so that it emits noise perpendicular to the antenna's sensitive direction?

Thanks

Answer 1

You will need to determine what switching frequency the SMPS is using. WWVB uses 60 kHz, and the SMPS probably only operates that low if it operates in a pulse skipping mode with light load.

If it does operate at 60 kHz, you could increase the loading on the SMPS (which is wasteful of power), but otherwise you won't be able to filter out its 60 kHz from the receiver.

Else, you need a lower bandwidth filter on the receiver. Often a 60 kHz crystal resonator works very well for this.

Answer 2

Place the DC SMPS inside a small diecast aluminium box with feed thuu or BNC connecters on it .This should nail it because it did for me on an AM BC radio retro project.Consider using a linear supply this is cheap and easy.Consider a SMPS that runs always above 60KHZ .Consider a sinewave SMPS that runs somewhere not harmonicly related to 60KHz.The other possibility is using an external Antenna and dispensing with the ferrite rod that picks up magnetic fields in your crowded room so well.In other words use a shielded tuned circuit or two resonating at 60KHz and loosly couple some coax to a outside Antenna.