On 3/7/2020 11:47 AM, Richard (Rick) Karlquist wrote:
A logical question to ask would be:
As an alternative, would it be sufficient to simply
bond the shield of the coax to the boom, such that
there is a free-space 1/4 wavelength of coax
between the driven element and the point of bonding
to the boom?
I haven't looked at that.
Also, it is surprising to see #31 cores at 50 MHz,
as opposed to #43 or #61, as Fair-Rite recommends.
#61 is a much higher Q part, and both parts tolerances and winding
tolerances come into play. I looked into Fair-Rite published data for 1,
2, and 3 turns of #31 and #43 parts, and #31 looked the best on 6M.
I notice that the 6 inch diameter 2 turn loops
have a free space electrical length of exactly
1 radian at 50 MHz. Is that just a coincidence,
or is that in some sense optimum?
It's a coincidence. I looked at Fair-Rite's data, noted above, wound
some chokes and measured, and liked what I saw.
Harold Wheeler
coined the term "radianlength" and noted that
it seems to be magic length where systems transition
from lumped element to distributed elements, etc.
Keep up the good work.
Thanks for all the comments. That 6M antenna is now in the air, and the
chokes are clearly working -- when I turn away from noise sources, they
are GONE!
73, Jim
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|