Power Supply Ferrite Beads.
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I would like some advice on the correct Ferrite beads to use in the P/S line
to minimize noise from a switching P/S. Though slightly off topic, with the exception you must get power to the Elecraft rig somehow and quite often it is a switching power supply due to their small size this is going to be used for my K2. I have read many recommendations on their use here but can't find the answers to my questions. I have spent several hours on the internet and the only conclusive information is "Don't get one of those split beads from Radio Shack as they are for frequencies above 30 MHZ." There was discussion on using type "75" or "77" "as this has a higher impedance at lower frequency" but that does not help me. My question is "What Ferrite Bead, Core, etc.? Can someone give me a part number. How big does it need to be so that 10 amps, 25 amps, etc will not hurt it? How many turns through the core? Should the wire (wires) be bi-filar wound or separated and wound on opposite sides? Thanks, Rich, KE0X _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In a message dated 16/05/05 23:08:10 GMT Daylight Time, [hidden email] writes: First, for the ac cord, use a large enough toroid so that you can get a number of turns through it. Try to get them to lay smoothly next to each other, rather than bunching and crossing over each other. You can remove the ac plug for the winding, then install a new one when the windings are done. Reply: ------------------------------------------------------- Like Bob, N6WG I used a large ferrite ring that was sold at a hamfest for use to construct a filter for hi-fi interference and TVI suppression at HF at about US$1.00 each. Through this wound as many turns of 3 conductor AC power cord that would fit laid flat with it's outer sheath removed. Ended up with about 12 turns secured with plastic cable ties. In my case was using this to suppress a noisy PC switched mode supply at HF so added an IEC free socket on the end of the short cable tail. The incoming power was taken through one of the shielded IEC chassis mounting filter with male connector that are available in the market. Mounted the whole lot in a plastic box with an added MOV suppresser to remove spikes mounted at the terminals of the IEC filter. This is only added for the benefit of the PC to prevent spikes causing system crashes. Mounted the box next to the power socket on the PC switch mode PSU to keep any leads short. Works well allowing me to have the PC running at the same time as working HF which was just about impossible before. Purposely suppressed all three conductors including ground which decoupled the PSU case and by default the PC to contain the interference sources. Noted that a commercial power filter for telephone switch use was found to be similar, with all three conductors including the ground lead decoupled with an inductors. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Rich Lentz
Hello Rich
Several suggestions. First, for the ac cord, use a large enough toroid so that you can get a number of turns through it. Try to get them to lay smoothly next to each other, rather than bunching and crossing over each other. You can remove the ac plug for the winding, then install a new one when the windings are done. This doesn't answer your question as to what material to use though. Here I have a shoebox full of "orphan" toroids, where I don't know their history. I use my antenna analyzer to check the impedance of a number of turns on a given toroid, and keep trying 'til I find one that gives a good impedance over the hf range. If someone can specify a particular core material that is known to be good, that is even better. Put the toroid as close to the switcher as you can, to minimize the amount of cord that can radiate hash. Second suggestion is to provide some spacing, say up to six feet or so from the radio. I'm assuming your switching supply is in a plastic case. That seems to be rather common these days. On the dc output side, place another toroid, as close to the power supply output as possible, again to minimize the amount of wire that can radiate hash. Use a heavy enough gauge of wire to minimize voltage drop though. For a K2, a heavy lamp cord would do nicely. Third suggestion is to be sure you are using either coax or a balanced feedline with balun. Either approach will have minimum pickup in the vicinity of the radio. The hash will have to go all the way out to the antenna to be picked up, and by then it should be too weak to be a problem (hopefully). Hope this helps you get started, Rich. Good luck and 73 Bob N6WG -----Original Message----- From: elecraft-bounces+n6wg=[hidden email] [mailto:elecraft-bounces+n6wg=[hidden email]]On Behalf Of Rich Lentz Sent: Monday, May 16, 2005 1:25 PM To: Elecraft Reflector Subject: [Elecraft] Power Supply Ferrite Beads. I would like some advice on the correct Ferrite beads to use in the P/S line to minimize noise from a switching P/S. Though slightly off topic, with the exception you must get power to the Elecraft rig somehow and quite often it is a switching power supply due to their small size this is going to be used for my K2. I have read many recommendations on their use here but can't find the answers to my questions. I have spent several hours on the internet and the only conclusive information is "Don't get one of those split beads from Radio Shack as they are for frequencies above 30 MHZ." There was discussion on using type "75" or "77" "as this has a higher impedance at lower frequency" but that does not help me. My question is "What Ferrite Bead, Core, etc.? Can someone give me a part number. How big does it need to be so that 10 amps, 25 amps, etc will not hurt it? How many turns through the core? Should the wire (wires) be bi-filar wound or separated and wound on opposite sides? Thanks, Rich, KE0X _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Rich Lentz
You may care to look at what I did to quieten a Samlex SEC 1223 as kindly
posted on Tom Hammond's website. http://www.n0ss.net/samlex_1223_rfi_mods_from_zl2df.pdf -- 73s, Nigel ZL2DF _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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