Hi, some tips: > 1. BU225s were worse than BUX80s (i.e. more noise) > 2. They wiped out the medium wave (560 -1600khz) and did not have the more limited effect of the BUX80s which notched out local stations and then just annoyed on the rest of the waveband
You probably just moved the problem instead of solving it. The easiest way to gandle this is borrowing a spectrum analyser (and antenna) somewhere. I got one for such purposes. > 2. Moving mains point did not solve the problem. It reduced it. For EMC, all cables must enter the equipment on one point. All grounds/shields must connect there to the housing. > 3. Moving to Battery power more or less did solve it. The radio became quite understandable, with noisy patches when the ferrite rod in the radio was end on to the interferance. So it was directional. I think that this may be only magnetic fields instead of elektromagnetic. elektromagnetic fields deacy with the square order of the distance, magnetic fields with the 3rd order, that is why it disappears on a distance. And magnetic fields only have one direction and not two components, this can explain that is much more directional. > This seems to confirm > a. That transistor equivelants were a bad idea > b. That the majority of the noise is coming through the mains. These low frequency's (0.1-2 MHz) need long cables to transmit elektro-magnetic (=radio) fields. So for example the mains cable. Using a filter may be a good idea. <note: 20 years ago this was high frequency to me, nowadays i test upto 1 GHz> Also standing waves often are a problem. You can solve that by placing a 50 ohm resistor in series with a capacitor across the mains lines at the entrance of the equipment. > c. That a mains filter might have been a good idea after all. Yes. > BTW, These diodes are a mains full wave rectifier, but have NO > electrolytic smoothing it. That's pretty unusual on a single phase. > That's where I'll start. I know, I know, electrolytics are useless at > hf, but it might keep the voltage up across those diodes. Tip: Place small capacitors, like 10 NF, across all diodes in the bridge. This often kills harmonics goin back into mains. I prefer however to find the source of the noise instead of solving all consequences. Regards, Pieter Hoeben ______________________________________________ Hoeben Electronics Phone: +31 6 51590081 Ronkert 44 Fax: +31 13 5096025 5094 EW Lage Mierde Private: +31 13 5096200 The Netherlands E-mail: [EMAIL PROTECTED] http://www.hoeben.com ______________________________________________ -- Author: Pieter Hoeben INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
