I need a variable capacitor / trimmer. I tried many different types and they where all of low quality. Do you guys know of a company that produce trimmer for around 20MHz approx. that has a high Q / low losses? I need one from 10 to 100pF and one from 50pf to 200pF that have linear adjustement. Had anyone ever try the trimmers of Sprague-Goodman :
The mica type (your first listed) will be the highest Q types you can get. The only other quality type are "Johansen", these use air dielectric, so won't be available in your capacities?
Frank
Those parts bring back old memories of using them in the mid 70'~80's so I looked them up.
Johanson, same range 1~30pF air tuner gold plated.
Sprague Goodman make them if you can afford them... $5~$25 ea.
If you need $1 solution, you need to redesign your requirements. Is this for a XTAL filter, VCXO or what?
Q > 400
price < 20$
pulling range : one from 10 to 100pF and one from 50pf to 200pF
temp stability : I will use it at room temperatur
What initial error at room temp : resonable
regards
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There are Crystal Oscillators (XTAL) that are variable?
Yes of course all oscillators are variable with voltage controlled capacitor diode and other methods.
I was reporting Q of the Crystal not the tuning cap. and error in ppm of each part. used in an osc .. read and answer again pls
You certainly do not need high Q caps to tune the motional capacitance of a XTAL oscillator... Can you post schematic or partial?
The Air trimmers are my choice. I will try one of thoses : http://www.surplussales.com/Variables/VariableTrimmers/VarTrimm5.html and maybe try to build the second example given by BradtheRad ( **broken link removed** ). What do you mean, the Q Factor of this home-made capacitor can be?