[NLRS] VHF low pass filters?

[Douglas H Reed]

Based on the WA4DSY filter design web page:

Bandstop filter, 52MHz center, 40MHz wide, 75 ohm impedance
Selected Chebeshev Tee filter layout.
	
Part Values
Part	Chebyshev 	Standard value
L1	0.2530 uH		240nh TK2707-ND
C1	37.03 pF		36pf
L2	0.1872 uH		150nh TK3102-ND
C2	50.03 pF		50pf or 22+27pf
L3	0.2530 uH		240nh TK2707-ND
C3	37.03 pF		36pf

Problem with the above filter because standard inductors are not that
close to preferred value. But the parts are listed as in-stock at
DigiKey.

Changing to a different bandpass or changing the impedance will make a
lot of difference in the filter components. You can juggle specs until
you get reasonable values to use.

51.5MHz Center, 35MHz BW, 75 ohms looked pretty good for 220nh or
240nh inductors. Personally, I'd prefer to stick with unshielded
inductors for higher Q. SMD parts have even lower Q than small
shielded inductors. If you download the spec sheet for the part series
it will probably estimate the tunable range for the inductor you are
looking at. Also need to look at the self-resonant frequency of the
inductors and caps used, especially if you are trying to cover the
whole 50MHz to 2100MHz frequency range in one system.

73, Dog Reed, N0NAS.