Re: a simple spur fix

Mike Woods

My guess is that the two intended filter frequencies are:  90Mhz (second harmonic of 45MHz 1st LO) and 12MHz (2nd LO).  The parts represent the right values for a filter at 90MHz, but it seems that 30M band would be wiped out by the second of the mods (which somebody has already observed).   12MHz should be being wiped out instead, so I suspect a typo.

Perhaps  either a 35pF capacitor and the 5µH inductor as stated or a 3.8µH inductor and the 47pF capacitor as stated being about right for getting the filter resonant just on the low side of 12MHz. 


On 10/11/18 9:49 AM, Brian L. Davis wrote:
10pf series with .3uhy - resonant about 91 MHz
47pf series with 5.0uhy resonant about 10.4 MHz
Is this correct?
Brian - WA5RDG

Mike Woods

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