As a hobby project I have slowly been building a high-performance HF receiver over the last few years. I originally used a switching power supply in it. Granted, I'm only slightly beyond newbie when it comes to switching power supplies, but I have to say that I found it impossible to keep the harmonics from the switcher from making it into the receiver. I tried shielding and massive filtering on the input and output leads to no real avail. I did not try magnetic shielding, however the physical separation between the switcher and the rest of the receiver was such that I would find it hard to believe that there could be direct magnetic coupling. I'm sure that it is possible to use switchers in receivers but I think that lots of effort would be required. I am not surprised if switchers are rare in receivers. Spectrum analyzers and scopes, on the other hand, are not nearly as sensitive, typically, as a receiver. I would think that they DO include switchers. Sean On Mon, Oct 20, 2008 at 8:53 PM, Justin Richards wrote: > When detecting very small rf signals is it possible a switching > pre-regulator will present a electrically noisy environment (all those > nasty harmonics) or can they be *completely* screened or perhaps > remotely located to eliminate the noise problem. If remotely located, > what would be a typical distance. > > I ask as I have seen a receiver setup where all the psu's are linear, > not a switching mode power supply anywhere in sight. I thought it > would have been much cheaper to go with switch modes but the designers > chose the expensive option. (expensive in my calculations) > > On a related issue, I would guess that psu's in sensitive test > equipment like spectrum and network analysers would only use linear > psu's. > > So my question is can switch mode power supplies be used in > electrically sensitive environments. Can quiet switchers be produced > or effectively shielded. > > Cheers Justin > > On Tue, Oct 21, 2008 at 2:43 AM, Olin Lathrop wrote: >> ala n smith wrote: >>> Yes..I know a switcher will do the job, but there are reasons for >>> using a linear in this application (low noise, RF, AF). And its not >>> my design, I'm just trying to circumvent the power problem before it >>> becomes an issue. >>> >>> The good ol 7818 and such in the TO-220 package are only rated to 1A, >>> but I need closer to 2A. Anyone know of a device, doesnt have to be >>> that package, that can go upwards of that current load? >> >> What voltage is it starting with. Power dissipation may be more of a issue >> than current. >> >> Maybe a switching preregulator followed by a linear if you really need >> quiet. >> >> >> ******************************************************************** >> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products >> (978) 742-9014. Gold level PIC consultants since 2000. >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist