[Elecraft] Good Low Horizontal Loops - questions

[George, W5YR]

Standing waves are a differential-mode effect and do not evidence
themselves on the outside of the coax braid. There are no "high-amplitude
standing waves on the (outer) shield of the coax." All standing-wave
phenomena are confined to within the coax.

The only times that radiation occurs from the outer braid is (a) when the
braid is not brought away from the antenna properly and signal is induced
into it to produce common-mode current and radiation and/or (b) an
unbalanced line is used to feed a balanced load without benefit of a balun
to isolate the outer braid.

Resonance has nothing to do with the presence of common-mode current on the
outer braid and lack of it does not cause feedline radiation. That is
strictly a balanced-current problem with balanced lines and a common-mode
current problem with coax. 

A balanced line does not ensure no feedline radiation. What counts is
balanced currents in the two wires of the feedline.

A visit to "Reflections II" by W2DU is recommended.

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437


k6se@juno.com wrote:
> 
> I wrote:
> 
> "If you feed an antenna for use on all bands, those bands it is not
> resonant on will have current on the coax feedline shield and the coax
> will also radiate -- an undesireable trait.  The feedline will not
> radiate if you use a balanced feeder."
> ==========
> The "current" I'm referring to here is the high-amplitude standing waves
> on the shield of the coax.  Balanced line will also have these big
> standing waves (on both sides of the line), but the currents in the two
> wires in the feeder are 180-degrees out of phase, effectively cancelling
> the feedline radiation.