[Hallicrafters] Orande dip, yellow tubular, and disc ceramic capacitors

[Peter Bertini]

Jim

You might also consider that the "Orange Drops" come in different flavors.
Both polyester and propylene dielectrics were used. Specs and prices are a
bit different.

I'd still opt for disc caps for RF bypassing apps.

Pete


On Fri, Dec 31, 2010 at 11:55 AM, James Liles <james.liles at comcast.net>wrote:

> We’ve been using all of the above capacitors in restoration for years and
> haven’t had a situation where one appeared better than the other.  My
> preference is the yellow tubular caps only because they are pleasing to the
> eye.  The following information represents the result of testing the
> components to enable practical, unbiased choices.  Assume measurement
> accuracy to be +/- 5% to 10% with consideration for component variations,
> lead lengths, and lead form.
>
> The .01 mfd capacitors:
> Ceramic disc ------  Self resonant at an average 8.0Mc
> Orange drop ------- Self resonant at  an average 10.0Mc
> Yellow tubular ----- Self resonant at  an average 9.0Mc
>
> The .001 mfd capacitors
> Ceramic disc -----Self resonant at an average 29.0Mc
> Orange drop ----- Self resonant at an average 26.0Mc
> Yellow tubular --- Self resonant at an average 24.0Mc
>
> See no reason to measure the ESR because the frequencies that these
> components service expect a minimum resistance of approximately 4 to 6 ohms
> which is very likely above the ESR.
>
> Things to consider.  Ceramic disc capacitors come in class 1, 2, 3, and 4.
>  Class 1 disc ceramic caps are the only group recommended for use at 30Mc +.
>  They can be identified by the NPO or C0G stamp.  The others can be
> unpredictable, lossy, and because the ceramic disc has Piezo properties can
> go off and do their own thing.
>
> The Orange dip and yellow tubular caps are not made like the old paper
> tubular caps.  The connection to the old paper caps was at the end of the
> roll of each plate whereas the new cap connections are to the entire edge of
> each roll significantly reducing the inductive properties.  The inductance
> including 1” leads for the Yellow tubular and Orange dip is somewhere around
> .04 uh of which a good part is lead length and shape.
>
> Another thing to consider is that self resonance in these caps is SERIES
> not parallel.  That means that as you move up the frequency scale to self
> resonance, the reactance drops to 0 ohms leaving only the resistance of the
> conductors.  From that point, say 24Mc using the .001 uf yellow tubular cap,
> as the frequency is increased, reactance begins to increase but will be
> inductive in nature.  The apparent inductive reactance at resonance will
> begin at 0 and increase not exceeding the original capacitive reactance
> until well above 30mc.  With this in mind, any of the .001 uf caps can be
> used at 30Mc for coupling or bypass operation with no measurable reason to
> choose except personal preference.
>
> If you are interested in the technique used to measure self resonance in
> these caps drop a note ---- needs a schematic to explain.
>
> Hope this helps to choose the appropriate cap when you reach for the box of
> parts.
>
> Kindest regards Jim K9AXN
>
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