[AMRadio] Cap Substitution

jeremy-ca km1h at jeremy.mv.com
Thu Feb 14 22:18:27 EST 2008

The cap is to reduce ripple to a level that wont cause chatter in the relay. 
A higher value cap reduces the ripple further and there is finally some 
finite value where the ripple is at zero.
Theory is in the PS section of any ARRL or other handbooks going back into 
the 20's.

I usually use 150-220 MF in such a circuit as I use 24VDC relays to do all 
my remote antenna switching and phasing. Again, it is not critical. If the 
relay doesnt chatter youre good to go.



----- Original Message ----- 
From: "JT Croteau" <jt.n1ese at gmail.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Thursday, February 14, 2008 9:13 PM
Subject: Re: [AMRadio] Cap Substitution

> On Thu, Feb 14, 2008 at 7:13 PM, Jim Wilhite <w5jo at brightok.net> wrote:
>> I read you are rectifying AC to power a DC relay.  If that is the case,
>> I would go to a higher value cap for the filter.  Say about 100 uf or
>>  more.
> Ok, and what would be the theory behind this.. I'm somewhat ignorant
> on some of this stuff.  The original schematic of the schematic I am
> repairing calls for 50 uF but I don't have that value in my junk box
> but I do have 47.
> Thanks
> -- 
> JT Croteau, N1ESE - Manchester, NH (FN42gx)
> Contest Manager, TARA Skirmish
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