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PostPosted: Mon Sep 08, 2008 4:42 pm 
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Pig
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I'm looking for some silver mica's, and as I need a couple of each of three values, I'm not likely to pay 15€++ (shipping) to get them from any EU seller.
So, if any EU member can help me...
33pF, 150pF and 330pF...
That's what I need... 2 of each value.
I can paypal/send money/bank transfer

edit: 33pF value corrected (was 3pF)

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PostPosted: Mon Sep 08, 2008 5:19 pm 
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I am pretty sure that I have the last 2 in my Junque Boit. First one.............nope.

If you can wait a long time until I make my next run of PCBs..........

Why SM? I only use them for RF stuff, and rarely ever these days

Jocko


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PostPosted: Mon Sep 08, 2008 5:31 pm 
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Yes, they are for RF.
You'll see it working... Soon :beee:

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PostPosted: Mon Sep 08, 2008 7:21 pm 
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audiopt wrote:
Yes, they are for RF.
You'll see it working... Soon :beee:

In my experience ceramic NPOs work just as well

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PostPosted: Mon Sep 08, 2008 9:09 pm 
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Here are 4 types os capacitors.

Is these NPO's you are refering to?


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PostPosted: Mon Sep 08, 2008 9:16 pm 
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No, I meant these:
Note black top.


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PostPosted: Tue Sep 09, 2008 6:08 am 
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SMT NP0s for RF is about the only place I use SMT.

In any case, SMs are overpriced, and I do not like them. Yes, ceramic can be nasty, but NP0s work nicely.

Jocko


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PostPosted: Tue Sep 09, 2008 8:32 am 
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10...50MHz ... Ceramic NPO's or SM's?...

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PostPosted: Tue Sep 09, 2008 2:58 pm 
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NP0. And at 50 MHz, I would go SMD. Yeah, I used to build 2 M ham gear 40 years ago with "dog bone" caps. But we don't have to these days.

Jocko


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PostPosted: Wed Sep 10, 2008 11:35 am 
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Jocko Homo wrote:
NP0. And at 50 MHz, I would go SMD. Yeah, I used to build 2 M ham gear 40 years ago with "dog bone" caps. But we don't have to these days.

Jocko

Hah. Having worked with endless through-hole RF equipment, in my day job and working with old VHF gear for 2M/70cm, I can honestly say that SMT is the best thing to ever happen to RF electronics.

In 99% of RF applications, C0G/NPO dielectric caps will work fine in place of a silver mica. About the only place you'll want to use a silver mica is in high current situations - AC coupling on the output of high power RF PA's, capacitors in high power RF filters, places where a MLCC will burn up.

You can sometimes parallel a few MLCC instead of a silver mica, but often times pad area will introduce too much shunt C or you'll have space constraints that'll limit it.

If you *absolutely* need a silver mica, let me know the dimensions and voltage rating you need and I'll see if I have them. What's this RF thing you're working on anyway? Got me curious.


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PostPosted: Wed Sep 10, 2008 1:24 pm 
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gmarsh,
No big deal of RF thing here.
It's just a crystal based oscillator and I want to have good caps on it.

Ok, you, Jocko and Elso convinced me to give up from expensive SM's.
I'll use the NPO's I have here. And I have hundreds of them, without knowning it :banghead:

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PostPosted: Wed Sep 10, 2008 4:37 pm 
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For what you are doing.............NP0 is fine. If you go the SMT route, you can stack them to get the right value. Within reason, of course.

Jocko


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