The AM Forum

Does anyone have the complete article ? I found one online but it stops mid sentence on page 5.
Amplified Elliptic Low Pass Audio Filters simplified and approved
Dallas Lankford 5/29/06 rev. 5/26/08
http://docs4.chomikuj.pl/1992242688,PL,0,0,ELPAFs.pdf

73 de k7iou

there is a yahoo group here that might have it.
http://www.kongsfjord.no/dl.htm

Thanks, I sent an email out to the group. I checked out the group before but was disappointed that nothing is posted there, files etc.
de k7iou

Elsie is a programm to calculate LC filters . The student version is free...   See   http://tonnesoftware.com/elsie.html
Interesting nice programm , works OK.  The input and output impedance is very important.  I use differential mains coils of 2x 50mH  and put the coils in serie to get a 200mH coil for less then a dollar. Adjusting is possible to add windings by drilling a hole in the center and ad the wire though it.
Perfect for designing lowpass audio filters. I measured some designs and if properly loaded the figures are as calculated.
see photo. a steep 3.5 kHz loww pass filter at 7kC 60 dB down 4kOhm in and output imp.
With small coil values the in and output imp is quite high. With big coils You can go low f.i. 200 Ohm or so.
Anton

I joined but no messages are allowed except by a moderator. There are no files posted. I don't understand why the group exists????? Seems worthless as a group to me.
My messages were returned,
to <thedallasfiles2@yahoogroups.com>.

Your message was not delivered because it was sent to an
announcement-only group, where only the moderator may post.

A copy of your original message is attached.

That's kind of silly. Maybe it is a cobweb, squatter, or placeholder.

I was very happy with Elsie as well as with Linear's program.

Getting off topic
Please keep it to the original post and question.

It seems appropriate to discuss where to find Dallas Lankford information, since that IS the original topic.

From what I've been able to gather Mr. Lankford pulled his work from the internet a few years ago and moved it to a limited access Yahoo discussion group.  I had tried to access that group a couple years ago without success.

Apparently during the Yahoo discussion group reorganization a year or so ago, the files were lost, leaving Lankford to rebuild...

I'm not sure what drove him to remove his works from public access.  It's quite unfortunate considering how prolific he was, and that he originally was inspired to share his knowledge.  b.

I am finding the "Wayback Machine" to be invaluable in recovering lost internet data.

Here is the Dallas Files from the kongsfjord.no (sp) website from Nov 2010.  This is the last archive date before the files were deleted in 2011/2012.
https://web.archive.org/web/20101124124237/http://kongsfjord.no/dl/dl.htm

I believe this is the last revision of the elliptical filters article updated 5/26/08
https://web.archive.org/web/20101124132846/http://kongsfjord.no/dl/Audio/ELPAFs.pdf

You can browse earlier capture dates using the forward/back arrows on the Wayback display.  bill

It most certainly is on topic and a good contribution to the thread.

Please resist the temptation to backseat moderate.

Thank you Bill! This is it :)
https://web.archive.org/web/20101124132846/http://kongsfjord.no/dl/Audio/ELPAFs.pdf
I was missing 2 pages. I believe Lankford's articles are a great contribution to the amateur radio community and I wish he would publish a book as I would be one of the first in line to buy one. 73 de k7iou

I'd forgotten about web.archive.  Went looking, and even found the ancient ham radio site (globeking.com) I took down many years ago.  It was fun to see some of those old pics :)

Grant NQ5T