[Boatanchors] Theory Question

[Jim Wiley]

Michael, Keith, et al:

Actually, you will sometimes find as many as 3 or even 4 different 
bypass capacitors in parallel,  a 10 to 220 uFd electrolytic for 
frequencies in the "power and audio" range, a .01 to 05 uFd ceramic disk 
for low RF frequencies, a .001 uFd disk for higher RF stuff, and 
occasionally even a 50 to 100 pF chip type cap for VHF and UHF ranges.  
Each capacitor type having characteristics that were suited for the 
different frequency ranges.   I first ran into this when servicing GE 
"Mastr  II" land mobile sets in the 70's and have seen it many times in 
other sets since.

- Jim, KL7CC



On 7/29/2015 9:07 AM, Michael Bittner wrote:
> Keith,
>
> You will often see two parallel bypass caps for the screen grid of 
> regenerative receivers that control regeneration by varying the screen 
> grid voltage with a potentiometer.  The purpose of the smaller of the 
> two caps (anything from 100 pF to 500 pF) is to bypass the screen grid 
> for RF since the larger one may become inductive at RF.  The larger of 
> the two (typically 0.1 uF to 0.5 uF) is for bypassing the screen grid 
> for audio and especially for the scratchy noises that may be produced 
> by the pot.
>
> Mike, W6MAB
> -
> -
>
> ----- Original Message ----- From: "Keith Densmore" <ve3gem at gmail.com>
> To: <boatanchors at mailman.qth.net>
> Sent: Wednesday, July 29, 2015 7:55 AM
> Subject: [Boatanchors] Theory Question
>
>
>> Have a question I know someone will know the answer to.
>> Very often in tube bypass capacitors, both b+ and cathode, two caps 
>> are used, a
>> lower value and a higher value, ie .01 and a .001.
>> What is the purpose of this, would not the .01 do the job alone? 
>> Never seen
>> this addressed.
>>
>> ---
>> New Outlook Express and Windows Live Mail replacement - get it here:
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>>
>>
>> Thanks,
>> Keith ve3ts
>
>
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