Hello All, every capacitor has a series self resonant frequency that is
determined by the lead inductance and the actual capacitor value.
Shorter leads have less inductance than longer leads and would have a
higher self resonant frequency.
For bypassing purposes it seems that the lowest impedance would provide the
most effective suppression. At higher vhf/uhf/microwave frequencies,
capacitors are often selected for self resonance to provide the lowest
impedance
possible.
73,
Gerald K5GW
In a message dated 4/3/2013 10:16:53 A.M. Pacific Standard Time,
k2vco.vic@gmail.com writes:
In a conventional 3.2 kV HV supply that I've built for my new amplifier, I
bypassed each
of the electrolytics with an 0.01 uf disc ceramic capacitor. My thought
was that there
will undoubtedly be RF leakage back to the power supply, and especially on
160 meters the
regular bypassing of the HV line might not be adequate to keep RF out of
the capacitors.
RF would be another source of heat that could shorten their life.
It didn't occur to me that it might be possible to 'resonate' the
capacitors at some RF
frequency and make the problem worse! I'm interested in the answer to
this, too.
On 4/1/2013 4:45 PM, Gene May wrote:
> 1. I've read conflicting recommendations about adding a cap that
presents a low impedance to RF, such as a .01 uF disc ceramic, in parallel
with
the MF filter electrolytics (in "switchers"). This would be to shunt out
the RF components of power from the switching circuitry. I've heard some
say "yes" to this cap, and others say "no" because it can form a resonant
circuit at some RF and overheat or cause instability in the switching circuit,
and others say it is a good idea but only if you use a cap that will
handle the probably high RF currents. What do you think about this practice
--
paralleling the electrolytics with disc ceramics for the RF? Would this
advice vary depending on whether the ripple frequency was 120Hz or 20 KHz?
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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