Hello,
I'm very close to finishing the receiver portion, but am a bit confused about the inductors listed for the RF amp and IF module.
The schematics on github show three of these inductors as 9.5uH, and does not label the two matching inductors on the IF module. The IF module schematic is also missing notation for many capacitors. (I made some assumptions here based on the capacitors parts list and other posts)
I thought the three 9.5uH inductors were expected to be hand wound, but then I realized I have a pack of (5) 22uH inductors from the parts list (which is way too many if the first three are hand wound)
I was hoping you would be able to clarify the schematics for the RF amp and IF module?
Thank you!
Sorry for the confusion, but thanks for helping to pin down errors. I need to compile a new combined schematics PDF. I prepared it before a few changes were made and that are reflected in the individual schematics attached to the module kits in the whole package. Since you have just the bare PCBs, of course you didn't receive those.
The inductors you refer to (L1 and L4 on the IF module, and L1 on the RF amp) are chokes to keep RF out of the power supply. Any value over the 9.5μH shown in the old schematics will work (even better) for that purpose. As finally implemented, these are the 22μH inductors you mentioned, and they're not hand wound. They're epoxy-dipped types that look like fat resistors. I tried to minimize hand winding as much as possible, and manufactured chokes are a good way of doing that.
The updated schematic for the IF module shows the shunt capacitors for the xtal filter starting as 68pF. Parallel caps can be used to narrow the bandwidth. The newer schematic shows the values for the two impedance-matching L-networks at each end of the filter (L2/C11 and L3/C20) as 5.1μH (on T50-6 cores) and 220pF (same for both ends). You may find you need to fiddle with these values to get a flat (unrippled) passband.
Please don't hesitate if you have any other questions.
Todd K7TFC
Awesome! Thank you!
No problem, just some slight re-configuring and burnt fingers lol
That's great, if you build the new schematics pdf, the parts list can be updated. I've done well so far with the existing list, but with the missing info, I couldn't verify it while building my list. That single IF Module page is a huge help.
Thanks again : )
