[ARC5] Bypass Cap Question

[Mike Feher]

Electrolytics do not do well with RF. They are great at low frequencies,
like power supplies and audio. While the low inductance ceramics or others
families are better at RF. So, the 0.01 will prevent RF from going back into
a rig more than a 100 uf electrolytic. 73 -Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of Mark K3MSB
Sent: Sunday, November 24, 2013 11:01 PM
To: ARC5
Subject: [ARC5] Bypass Cap Question

Hi Guys --

Getting back to work on my SCR-274N issues, namely the nasty buzz on 40M as
related in previous posts a few months ago.

I haven't had time to do much work on this since then as life has gotten in
the way.   Our first son has left the nest and is in basic training at Ft
Sill in Oklahoma;  this was a big "event" for Barb and I to deal with as you
probably can well imagine.

It was suggested to me that I bypass all the power leads with a 0.01 uF cap.

Now, we all know that Xc = 1 / ( 2 * PI * F * C).      Since my power
supply has about 100 uF in the filter stage,  the capacitive reactance to
ground will be

1 / (2 * PI * F * 100).

This is less than 1 / (2 * PI * F * 0.01) which is what the 0.01 cap will
provide.

So, what's the point in adding the 0.01 uF caps to each of the power leads,
since I derive them all from a common line (using the classic divider for
the transmitter)  and there already is 100 uF between the 550V line and
ground?

73 Mark K3MSB
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