Chuck,
MRCC? do you have a link for that.? I like and use for torroid winding calculation. You can click on the torroid type and enter inductance or turns.?
---John AC9UV
? ?73
On 04/14/2023 5:05 AM Chuck Carpenter <w5usj@...> wrote:
Davey,
Looks like you have the toroids figured out.? T37-6 would be yellow.
A utility I like for inductors is Mini Ring Core Calculator. Find it on the web.
I assembled the N4ELS filter, aka the QRPme HPF filter kit;
a basic filter using common part values. Toroids are T37-2.
The nanoVNA was used to get sweeps of toroids at 1.8uh and 1.5uH.
Results were pretty much the same with 1.5 having better input impedance.
This is a broad cast band filter. It won't do anything to help SWI short wave interference.
A second higher frequency LPF would help with that problem. As is, between 500kHz and 1.6MHz,
the attenuation ranges from about-70dB to -40dB
Note that the combination looks a lot like a BPF...8^) That was attempted but...
If the SWI is from a single station, a series-tuned notch filter would help. MRCC has a feature
that helps determine L/C values using F of station.
To cover lower bands, the components get more complicated and use values that are
not standard.
