[ARC5] Power Supply Filter Question

[Bruce Long]

It might offend the traditionalists but in my opinion power semiconductors are so cheap that active - as opposed to passive LC filtering- needs to be seriously considered.  Bruce   KJ3Z





On Friday, December 20, 2013 9:35 PM, K5MYJ <macklinbob at gmail.com> wrote:
 
If there are two capacitors and an inductor in the supply you could try 
leaving out the input capacitor. The output of an inductor input filter is 
lower than that of a capacitor input filter.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "Robert Eleazer" <releazer at earthlink.net>
To: <arc5 at mailman.qth.net>
Sent: Friday, December 20, 2013 6:04 PM
Subject: [ARC5] Power Supply Filter Question


> Back when I first started learning about boatanchors I read the usual ARRL 
> material that described the classic way to build a power supply: a 
> capacitor, an choke inductor, and a capacitor.  I soon found out how rare 
> and expensive the required inductors were.
>
> I was amused last year when I rebuilt the AC power supply on a BC-348-N. 
> It was classic - literally right out of the Surplus Conversion Manual - 
> using two fairly low valued high voltage caps and a pretty big inductor. 
> I used some new, bigger, caps when I rebuilt it but left the inductor in 
> place.  Of course, it was also running the B+ way too high and I added 
> some power resistors in both the AC input line and the B+ line.  Got the 
> B+ from over 250VDC down to about 200 VDC.
>
> Now, we have available high voltage caps that have much larger values that 
> those 20 mfd cans we used to use and are a lot smaller as well.  But I 
> wonder if adding some inductance to the power supply circuit would do some 
> good?  Would winding some wire around a piece of steel or even around a 
> nail provide better filtering than just some big caps?
>
> Thanks,
>
> Wayne
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