[Elecraft] xtals 7-11

[Bill Coleman]

On 3/7/03 9:45 PM, Martin AC6RM at elecraft@ac6rm.net wrote:

>OK what is "blow-by"?  I have heard it used in reference to receiver
>sections but I have absolutely no idea what it means.

The objective of the crystal filter is to pass certain freqeuencies, 
while rejecting nearby adjacent frequencies. Outside the passband, the 
crystal filter will have rejections greater than -60 dB (eg 1 in 
1,000,000 or more).

However, if minute currents manage to capacitively couple from each 
crystal face, they may get from the input to the output of the filter 
lattice -- essentially bypassing the filter. Hence "blow by".

I believe "blow by" is a descriptive term borrowed from mechanical 
internal combustion engines -- referring to the combustion products that 
managed to get past the piston rings and into the crankcase.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901