Posted by
Jim Brown-10 on
Jan 09, 2018; 9:33am
URL: http://elecraft.85.s1.nabble.com/PAR-LNR-EFHW-antenna-tp7637237p7637259.html
On 1/8/2018 8:19 PM, K9MA wrote:
> I would be cautious about using a transformer above 40 meters, as the
> stray capacitance may be too large. I haven't tried it, though, so it
> might work with some transformers.
For years, we've been winding our transformers wrong. The windings
should be on opposite sides of the core, so that capacitive coupling is
minimized, NOT laying on top of one another. In a ferrite materialthat
is SUITABLE for use as a transformer, the mu is high enough that a VERY
high fraction of the flux in toroid is contained within the core, with
very little leakage flux. Windings that lay on top of each other
maximize capacitive coupling, and thus maximize common mode current.
Windings on opposite sides of the core minimize common mode current.
Ferrites are semiconductors, so they act as a dielectric. When we place
windings on opposite sides of a core, we maximize magnetic coupling and
minimize capacitive coupling, which is from one winding to the core and
from the core to the other winding. That capacitance is VERY small if
the windings are widely spaced.
73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.htmlMessage delivered to
[hidden email]