[OFARC] FW: Filter project

[Ralph (home)]

Again …. Band pass filters block radio frequencies above and below the band you want.

So ….  The 20m band extends from 14.0 mhz to 14.35 mhz.  The filters we built last time block everything higher frequency than about 15mhz and lower than 13.5 mhz.

That eliminates the 7 mhz harmonics from 40m and the 28 mhz harmonics of 10m.

 

The filters we built before are simple …. Some coils and capacitors.

We found them on the web listed as the NVARC “Ugly filter project”

Here is the web page….   https://www.n1nc.org/Filters/

All details for several bands are included on the pages.

 

The capacitors they list are  no longer available, but the technicians at Mouser.com (electronics parts) helped me find some replacements.

 

There seems to be a consensus to build the 20m and 40m band pass filters.

I have decided to just use the same part numbers we had before…. Go for quality

The cost of capacitors is $16+shipping for each 20m or 40m filter.

 

We will make the coils ourselves from wire wrapped on pvc pipe.

 

Other parts needed …..a metal box , 2 coax connectors, solid copper wire, pvc pipe, misc. screws and nuts.

 

I expect the total cost to be $35-$40 per filter (assuming my previous source of boxes is still  open)

We can take a head count at the next club meeting and order parts

I will bring a filter and explain the fabrication techniques I used.

 

Ralph

KE5HDF …

 

P.S.     If anyone wants a filter for a different band, I can help them find suitable parts at Mouser.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/ofarc/attachments/20170810/140f2098/attachment.html>