RE: [softrock40] Re: Switching power supplies
Switching power supplies generally use radio frequencies to manage the voltage and amperage exchange. I assume that good ones have decent filters to keep the interference to a minimum. If they radiated a lot you would hear it in your computer sound system. The only caveat is that the softrock radios are sensitive and they also are reliant on the computer sound system.
Alan – W6ARH
The answer varies all over the place, some are very quiet some are horrible, and some are in-between.
I own several Samlex 25A power supplies out of 5 one was noisy, the others were pretty quiet, so I took all 5 apart and the wires heading for the output connectors were wound around a large Ferrite core with multiple size capacitors to ground (.001uF, .01uF, and .1uF of good quality) all five are quiet as a church mouse.
On the other hand my Dell laptop when running on batteries can be heard all over the spectrum, while plugged in it's not too bad.
At 04:49 PM 10/21/2011, you wrote:
I tried a couple of switching supplies with Ensemble RX II and Ensemble VHF, both from old cellphones. The hash was terrible across the spectrum.
I've found one switching PS 12V/2A that is quiet above 10MHz. Using it with my FT-817.
As for RX Softrocks, the smallest linear wall warts (100-150mA) seem to give the best results. They are also usually free or 25c at garage sales.
The RX lineup has a 7805 regulator, so the supply doesn't have to be regulated.
--- In email@example.com, Preston Douglas <pdouglas12@...> wrote:
> This is a general question about SDR rigs and switching power supplies. One of my linear 12v supplies was drowned in a basement flood thanks to hurricane Irene. I am thinking of replacing it with a small switching supply from MFJ, particularly since it can sit on the operating desk without stressing it with the weight of an equivalent linear supply. One of the reasons I lost the linear supply was that it was mounted on a shelf near the floor, so the water reached it. It would be safer up on the desk. So, are any of you using a switching supply with an SDR rig (Softrock, Flex, etc.) and if so, are you getting a lot of hash on the panadapter?
> Preston WJ2V
- Take care trying to use old cellphone wall-wart's as "PSU's".
Many are not PSU's as such, but Chargers. As such, they do not regulate
well (if at all) with a very light load, such as an SDR.
Also, those that do regulate, might do so, in a way that changes the
"mode" of operation of the Switcher itself, from Continuious to
Discontinuious mode, dramaticaly altering it's RFI spectrum, making any
filtering it has less effective than it might be in "normal" use..
Joking apart, sometimes adding extra load to some small (and large)
SMPS's, can help keep them quiet(er) than they would otherwise be.
Go for about 30% or more of their nominal rated output. Check on the
ratings plate, label, embossing, for what they are rated to provide, some
are suprisingly powerfull, but most are not easy to read that data from.