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Mica chip caps to replace ceramic or porcelain

PostPosted: Mon Jul 16, 2007 6:05 pm
by John K5PRO
Good ol' Cornell-Dublier electronics has some hefty new HV/RF mica chip capacitors, low loss, that might work well in a class E as shunt caps or other.
Price is ~$5 or more. Value only up to 220 pF though.

Supposed to be mechanically better than the big ATC 100E porcelain style.


http://www.cde.com/catalogs/MCH-MCHN.pdf

PostPosted: Mon Jul 16, 2007 9:54 pm
by kf1z
Interesting cap....

Data sheet does say values to 1000pf (2500wvdc).


Must be an updated data sheet, I have one on file for the same caps, dated 01-01-2005... this one is 06-19-2007....
I'll have to compare them side by each, and see what's different...

I am confuse by the "Allowable voltage VS frequency" chart....

Would lead me to believe that they don't want you to put more than 850 volts pk to pk across a 4500 vdc cap........??

The Q doesn't look as high as the atc 100c.
Maybe not an issue......

Big question is .... are they available?

I called ATC 2 weeks ago..... still waiting for a price quote!

I believe they blew me off because I'm "not a big enough company".....

FINE, I won't USE their caps........



I'm goint to check into these....
I used the MCM from CD in my last transmitter.... and they worked just fine....
never got warm...... and they're only $3 each.... (Mouser)



At any rate... thanks for the info!

Peak voltage rating

PostPosted: Tue Jul 17, 2007 1:59 pm
by John K5PRO
I think the voltage rating for RF p-p across the capacitor is limited by the maximum RF current allowed,which is why it changes with frequency. It is less than the DC WV rating, sometimes by a lot....

PostPosted: Wed Jul 18, 2007 12:43 pm
by K6IC
Hi Bruce, OR ANYONE,

Quote, "
I'm goint to check into these....
I used the MCM from CD in my last transmitter.... and they worked just fine....
never got warm...... and they're only $3 each.... (Mouser)

At any rate... thanks for the info... " (I cannot seem to make "quote" work)

Is this a quote from some one else?

OR: Has anyone used the CDE MCM series caps in 220 pf or 470 pf@1000V as shunt caps in 160/75 Meter Class E rig ?

If so, how did they work? Comments ?
My first Cl E rig will use discrete C's for shunt C, perhaps later will use Kapton/spreader approach ... THANKS, Vic K6IC

PostPosted: Wed Jul 18, 2007 2:00 pm
by kf1z
Yes Vic,
That was my quote.......

And a partial of another post of mine......

Since that "MCM" ppost....I ordered, and use the metal clad micas..... and they worked ok.....

I did have a little ripple on the drain waveform , but I believe that was due to the skimpy leads I attached them with ( stray "L"..)


My opinion is.....

For the difference in price, (between the MCM01, and the ATC100C), I would go with the ATC100 C series caps...
They are going to be about $4 each WITH leads attached.

And the Metal Clad are about $3....


Right now I'm using the Copper/Kapton approach, and very happy with the results.
(for single band only.....or, you'd have to switch in other caps for lower frequency)

PostPosted: Wed Jul 18, 2007 3:12 pm
by K6IC
OK, Bruce,

Thanks for the reply. Did download the 100 C series DS. May have a question re the value B4 ordering them.

TU again Vic K6IC