Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Interesting filter design video




 
The AM Forum
April 13, 2021, 06:45:16 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Interesting filter design video  (Read 266 times)
0 Members and 1 Guest are viewing this topic.
WA2SQQ
Contributing
Member
*
Offline Offline

Posts: 906


« on: March 28, 2021, 12:55:39 AM »

Interesting video on filter design. Iíve not seen this design before. Iíve been following this guy for some time. Daily short videos that are very informative. Heís a ham, but I donít know his call. Anyone know how to model his design in Spice?

https://youtu.be/1aYp-RNpHDA
Logged
M0VRF
Member

Offline Offline

Posts: 125


« Reply #1 on: March 28, 2021, 04:17:27 AM »

Looks like the response of a elliptical filter. However there is loss in the passband which is unacceptable. Looks like winding the 2 inductors on the same former simulates the parrallel capacitance normally associated with elliptical filter by using stray/coupled capacitance of the proximity of the 2 inductors. I don't see the point in investigating it any further, it may be novel but the response won't be optimal and will be a pita to tune.

Interesting tho'

JB.
Logged
ka1bwo
Member

Offline Offline

Posts: 140


« Reply #2 on: March 28, 2021, 10:47:15 AM »

 Evaluate the inductor by making a S21 measurement with a VNA. Then apply it to spice.   
Logged
Tom WA3KLR
Contributing
Member
*
Offline Offline

Posts: 2038



« Reply #3 on: March 28, 2021, 02:02:35 PM »

I hadn't used LTSpice in so many years I had to delete it and re-install to get the latest version. I simulated his original 2 section lumped inductor pi filter using his capacitor values and since the inductors are stated as 15 turns only (both the same value) I re-ran the simulation and changed the inductance value until I got a nice 40 meter low-pass filter response using 1.47 uH inductors. As I presumed, the current in the two inductors is different by 108 degrees at 7.3 MHz. so I don't see how his version is going to work well. 20 meters was down 22 dB (no losses in the simple parts simulations). BUT I have not taken the time to try his transformer (mutual inductors) version yet.  

I haven't done this in many years, but as I recall to define a transformer in LTSpice, you have two inductors with a coupling constant.  A 1:1 transformer is modeled as both inductors same inductance value and say a coupling coefficient of 1, statement/Spice directive:   K1 L1 L2 1.
Logged

73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.086 seconds with 18 queries.