[TowerTalk] Ferrites 31 vs. 77 material

[Bob Shohet, KQ2M]

This has been an interesting tangential discussion but I would like to now bring it back to my original question......  :-)

So far, taking into account the tolerance caveats, the consensus seems to be to use 31 material going forward rather than 77 material.

I prefer to use large ferrite beads that fit on the coax – roughly 1/2” ID -  1” OD  x 1 1/4” height and then tape the beads in place in physical proximity  to each other next to the feedpoint.

All coaxial cables used for 4 –square phasing lines are cut for an electrical 1/4 wavelength   (RG11 Foam)
All coaxial feedlines from the antenna to the radio are cut for a multiple of an electrical 1/2 wavelength.  (RG213 or Buryflex)
For the 40 meter wirebeam I use an electrical 1/2 wavelength of RG8X followed by 1 wavelength of Buryflex.

In order to provide enough resistance adequate for an effective choke,  how many 31 beads should I used on each phasing line or feedline for

1.8 mhz?
3.6 mhz?
7.1 mhz?
14 mhz?
21 mhz?
28 mhz?

That is for the feedlines and the phasing lines.  But what I have also read is that I should also be using ferrite beads at the amp input and amp output.  Have I understood this correctly?  Should I then also use beads at the output of the radio?  Should these beads also be 77 material?

Is there any issue if the antenna beads are one type of material (43) and then you use 77 material for the amp/radio inputs/outputs?

Thanks in advance for your help!

73

Bob  KQ2M