Re: Series DC Blocking cap.
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Indeed
they do. The current handling / rating is usually defined by the capacitor¡¯s
Equivalent Series Resistance / ESR and its dielectric losses Dissipation Factor
/ loss tangent which is highly dielectric material dependent.
?
High
K dielectrics tend to be lossy while NPO class dielectric leaded ceramic disk
capacitors generally perform much better where significant RF current is
flowing.
?
Leigh
VK5KLT
?
From:
ham_amplifiers@...
[mailto:ham_amplifiers@...]
Sent: Friday, 28 June 2019 1:53 PM
To: ham_amplifiers@...
Subject: Re: [ham_amplifiers] Re:
Series DC Blocking cap.
?
Capacitors
have current ratings too. Voltage is one parameter and the current rating is
another.
Lee, w0vt
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On 6/27/2019 11:14 PM, jim.thom@...
[ham_amplifiers] wrote:
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##?
1500? watts? =? 5.5 amps into? 50 ohms.? That's a
helluva lot of current.? The problem? with? disc ceramic caps
is.... they never post any RF? current ratings on them.?
?Ideally, they should post a? ?CCS? RF? current?
vs? freq chart.? ?Actual? current ratings are all over the
map...and must be? determined by testing.?
?
##?
Big difference between? a .01 uf? @ 1 kv rated cap... vs a
.01uf? @ 2 kv rated cap... the 2 kv? versions are typ bigger diam,
like 25mm? OD... vs the smaller diam? 1 kv units.?
?The? 2 kv versions, being bigger diam, handle more current..which
testing confirms.? ?Once you get to the? 3+? kv rated
units, they don't appear to handle any additional current,? just a greater
V? rating.?
?
##? I
bought 2 x doz? .01uf @ 1.3 kv? disc ceramics? from RF
parts? last year.? Huge things at? 25mm? OD, and really
thick.? ?These things handle loads of current, best yet so far.?
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##
For? your heath switch box application,? parallel a 2nd cap? in
the remote switch box...then re-test.? ?Parallel a 3rd cap if
required.? ?You should have zero heat..on any freq.? Dunno if
the heath? box is? good up to 6m or not.? ?
?
Jim?
?VE7RF
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Leigh Turner