Mike,
here is a link to a good filter design program that is free:
http://www.aade.com/filter32/download.htm
This will let you explore some filters. I use this program at work and it
saves lots of time.
The 90-deg coax stub looks a bit to 1.8MHz though. Using RG213 that is
90-deg at 1.4 MHz, the impedance of the filter, when terminated into 50 ohms,
is
1.7 +j0 ohms at 1.4 MHz and 10 +j18 ohm at 1.8 MHz. Making the stub 277 deg
gives 5 +j5 ohms and 45 +j3 ohms. That's 13 dB of attenuation at 1.4 MHz.
Dave WX7G
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