Re: UBITX filter bandwidth
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I did see some online calculators for calculating the capacitor values.? Like you said it depends on the value of each crystal.? I don't think it is worth it for me to remove the crystals and do all the required work.
I though someone may have already done some work with filters of that kind and would have an idea' of about how much to change the values to get around 2 khz of bandwidth instead of the 1.6 khz I seem to? be getting.? ?Then there is the ripple and impedance that may or may not be worthwhile to worry about when doing this small move.
I have a lot of the smd capacitors and the hot air station to make changing it easy.? I just wish it was? going up in value as like you say it is easy to stack the components.
On Thu, May 24, 2018 at 6:21 PM, ajparent1/KB1GMX <kb1gmx@...> wrote: its easy enough to alter the capacitor values.? To what is a guess by anyone that answers
as your crystals may be different from someone else.
Try lowering all of them by 15% and remeasuring.? You will find out how it goes.
FYI 68 and 82 are standard values.? If you need odd non standard your take say a 56
and add a 15 on top to get 71 for an example.? When I say stack them SMT caps are
easily stacked like bricks.
The usual procedure to make a filter would have you measure all the crystals then grind
on the result and it will predict a capacitor value and terminating resistance.? ?And usually
when I do that I fixture it and measure it before stuffing it in a board.
Allison
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