Eric,
Thanks for all the answers.
I'm no expert on SAW filters, or anything RF for that matter.
But have read that impedances on a SAW filter can be modeled as a capacitor from input to output,
with a fairly high resistance in parallel.
The series inductors on input and output cancel out that capacitance, making the impedance look resistive.
With two SAW filters in series, there's effectively a very large capacitance between the two.
Adding an inductor in the middle would cancel that out.?
Or perhaps could double the inductance at each end instead?
On the other hand, if it works well, that's good enough!
And I could be wrong.
I like the looks of the 120khz wide B3780 SAW filter, very sharp, good stopband.
Perhaps a 415mhz+(0-250mhz) LO into an ADE-1, two B3780's feeding an AD8310.
An MMIC for gain if needed.? The AD8310 can respond very quickly for fast sweeps.
When a narrow detection bandwidth is needed, inspect the 415mhz using an Si4432?
Though your tinySA would likely be all I need,
Being retired, should have plenty of time available for long sweeps if using the B3780.
?
I've been watching the various SA projects you post here with great interest.
All of them very cool!
Jerry, KE7ER
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On Thu, Dec 26, 2019 at 02:35 AM, <erik@...> wrote:
Build photos appear to show two SAW filters directly connected, would it not be better
to have 2x the recommended matching inductance between the two?
Could be but as the input and output impedance are the same I assumed you could couple them also directly
?
