[TowerTalk] Fair Rite Type 31 Info

[Dan Hearn]

You can find information on cores suitable for line choke construction here.
http://www.fair-rite.com/cgibin/catalog.pgm#select:freq1
1. Single click Suppression.
2. Click Cables.
3. Click round cables.
4. Select either EMI for solid cores or Snap Its for split cores.

  Select any core and you will find the dimensions and the impedance for 1
turn at any selected frequency. This is R+Xl The impedance goes up as the
square of the number of turns through the hole in the core. Cores can be
bought from Mouser and other electronic dealers.
  K9YC has written extensively on test results for many choke designs. Here
is a good place to start learning about good choke designs which maximize
the resistive component of the impedance so that it covers several bands
and will handle legal limit power.
http://www.audiosystemsgroup.com/RFI-Ham.pdf
  Jim's pdf's are very large and cover a lot of stuff besides line choke
designs. You can jump to the part near the end to save time, Hi.
  I have designed and measured a number of line chokes and the results are
similar to Jim's. I usually use small teflon coax like RG142 in my designs
to make them smaller. This coax is good for 9kw at 10mhz, amazing isn't it?
  I hope that this brief note will inspire more hams to build good chokes.
A lot of the older designs are not very good, and frequently will overheat
if they are cast in epoxy.

73, Dan, N5AR


-- 
Dan Hearn
N5AR