Hi Jason, There are a couple of things that look wrong. The inductors say "nf" you pr= obably meant "nH". Also the MMIC you are using seems to be characterized at= minimum of 4.5VDC so they may not work at 3.3V. The 270ohm will certainly = make that voltage much lower so I don't think your first stage will work at= all. You should place a relatively high value (uH) inductor or choke to de= couple VDC from RF noise. Signal coupling capacitors, such as C1 or C5, should typically be at least = 10x preferably 100x the value of any filter involved capacitor. Except you = have good reasons for C1 and C5 to have direct influence on the filter impe= dance, they should be 100nF or higher for not having an effect in the AC si= gnal path for the frequency of your interest and values of designed BPF. Sa= me about C6 and C8. As for impedance, certainly has a major effect on how the amplifiers and fi= lters will work. The quickest way is to use LTSpice or similar, as others s= ay, it takes a few minutes to simulate your circuit for a range of frequenc= ies. Best Regards, ---- Ariel Rocholl http://www.rf-explorer.com -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of= Jason White Sent: Sunday, July 26, 2015 21:55 To: Microcontroller discussion list - Public. Subject: [EE] How to figure the load presented to a LC bandpass filter? Reposted with [EE] tag, fixed typos .... Disclaimer: I am a hobbyist and the design of RF circuits is outside of the realm of my= immediate experience. I am not asking you to calculate the values for me, I am only trying to det= ermine the load posed posed to the filter by both the input signal, and the= output signal. (The input impedance does affect the filter, right?) I am trying to calculate the appropriate values for bandpass filters in the= attached circuit. My question is: when two capacitors are used to couple a= signal into and out of a parallel LC filter over a wide band, how does tha= t affect the load seen by the LC filter (and its Q). How do the coupling capacitors, which are not direct connected to ground or= the supply rail but rather though a resistor or some other device, affect = the frequency and Q of the bandpass filters. (Like in the circuit attached) I know this is a big, nebulous question which is difficult to address compl= etely. When possible, tell me what I should actually be asking. Attached is the circuit which I am working to build, if I have a topographi= cal errors, I'd appreciate any advice I can get. The goal is for the circuit is the amplify the entire broadcast AM band (as= picked up by a long piece of wire up) to levels greater then 100mV with a = 50 Ohm impedance. Thank you, Jason White -- Jason White --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .