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<div align="left"><font face="Arial" size="2"><span style=" font-size:10pt">On 1 Nov 2015 at 20:11, Ron wrote:</span></font></div>
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<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> I built an 18vdc 1.5 amp power supply using a transformer, bridge</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> rectifier and a 7818 regulator. Works fine, but I need to go to 3 amps.</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> I have been trying laptop switching power supplies that put out 3 amps</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> that produce noise on my hf rig. If I unplug the laptop power supply,</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> the noise goes away. The power supply is used for charging batteries</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> through a solar charger.</span></font></div>
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</span></font></div>
<div align="left"><font face="Arial" size="2"><span style=" font-size:10pt">You can easily "boost" that by simply using a "pass transistor", connecting the output of
your present power supply to the base. Look in any older handbook for details.</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt"> </span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> Questions: what is the difference between a regular power supply and a</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> switching power supply?</span></font></div>
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<div align="left"><font face="Arial" size="2"><span style=" font-size:10pt">There is a lot of difference, too many differences to go into here.</span></font></div>
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<div align="left"><font face="Arial" size="2"><span style=" font-size:10pt">> Can I filter out the noise on a switching power</span></font></div>
<div align="left"><font face="Arial" color="#0000ff" size="2"><span style=" font-size:10pt">> supply?</span></font></div>
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<div align="left"><font face="Arial" size="2"><span style=" font-size:10pt">Yes, but such filtering has to be built into it from the design stage.</span></font></div>
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<div align="left"><font face="Arial" size="2"><span style=" font-size:10pt">Ken W7EKB</span></font></div>
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