Re: 45Mhz crystal filter specification
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You must use the L network of the ubitx or use 1:9 balun to get the proper shape of the fiilter. The 45 MHz crystal filters usually have a termintion specified for around 600 ohms.?
Let me bullet this : * All filters have the specified shape only when they are terminated at the specified impedance on both sides. * The passive filters, including the crystal fitlers have no measurable termination to speak of at all. They have different responses at different impedances.? * The capacitors of the ladder filter set the bandwidth. * The termination impedance sets the ripple. Lower impedance brings steeper skirt at the cost of ripples in the bandpass. To remove the ripples you increase the impedance and lose the sharpness of the skirt.
On Sun, May 6, 2018 at 7:45 PM, Tim Gorman <tgorman2@...> wrote: I'm using a direct probe. The 815 has a 50ohm input which should be a
match to most points in the ubitx. At least a close enough match to not
directly affect the circuits operation. I suppose I could use a 10x
scope probe but I'm not sure that would make much difference.
tim ab0wr
On Sun, 06 May 2018 01:03:42 -0700
freefuel@... wrote:
> Hi Tim,
>
> I'm interested to know how your connecting your SA to the circuit,
> from my recollection the majority of SA equipment has a 50 ohm input
> impedance, an input impedance that low is not conducive to hanging a
> probe off the circuit at any convient location.?
>
> -Justin N2TOH
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