1. Chart about which bypass cap to use versus frequency
Some sweeps of a few 100 nF caps from our collection. Starting with leaded values.
Above — TDK FA26NP01H104JNU06 -- a C0G/NP0 part. Multilayer Ceramic Capacitors MLCC - Leaded 50V 0.1uF NP0 5% RADIAL. We don't usually apply C0G(NP0) caps for HF bypass because of high cost. This is the deepest series resonant frequency notch for any leaded capacitor we've ever swept.
We use this particular cap for HF bypass in LC VFO tank circuits due to its temperature coefficient of 0 ±30 ppm/°C --- and as a low ESR cap in rare circumstances. For example, the cap coupling a low impedance loop HF antenna and its low impedance antenna amplifier input.
In a loop antenna plus amp, coupling them with Y5V or Z5U 100 nF cap usually offers a higher ESR and may reduce loop antenna gain, Q and increase noise figure compared to low or ultra low ESR caps from measurements done by Chris Trask. (Arizona, U.S.A.)
The suggested ultra-low ESR Porcelain caps like the Kyocera AVX 800B series (C0G) are too expensive for us, so this particular TDK part works OK as a leaded part for a low ESR capacitor.
Above — From a bag of 200 Siemens/ Matsushita (company now defunct) leaded, 50v X7R 10% that we purchased in 2000. Reasonable for HF bypass, but long obsolete.
Above — No name blue capacitors 104K 50v X7R. Pretty lame and low Q or high ESR. We use these for throwaway after building, HF breadboard experiments.
Above — KYOCERA AVX multilayer Ceramic Capacitors MLCC - Leaded 100V 0.1uF X7R RoHS Long Leads 10%. Better than the no name blue caps above, but can we do better?
Above — TDK-FA28X7R1H104KNU06 in X7R. Multilayer Ceramic Capacitors MLCC - Leaded 50V 0.1uF X7R 10% RADIAL X7R. We currently use these as our bread & butter HF bypass cap ( for through-hole part projects). A reasonably deep notch for a X7R TC capacitor.
Chip cap example:
Above — TDK SMD/SMT 1812 Low ESR & ESL in C0G Manufacturer # C4532CH1H104J200KA. Multilayer Ceramic Capacitors MLCC - SMD/SMT 1812 50V 0.1uF CH 5% This part is at end of life and cost us $1.76 CAD for 1 piece to test out. The SRF rose to ~ 13.4 MHz due to no leads, plus low ESL. A pretty nice part for SMD/SMT HF bypass, but quite costly for a hobbyist --- but a lot cheaper than a porcelain cap if you need a low ESR coupling cap in a jewel project.
3. What bypass cap value for 3.5 MHz?
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