Thread: Vincent antenna
View Single Post
  #425   Report Post  
Old December 5th 07, 03:46 PM posted to rec.radio.amateur.antenna
Richard Fry Richard Fry is offline
external usenet poster
 
First recorded activity by RadioBanter: Jun 2006
Posts: 440
Default Loading Coils; was : Vincent antenna

Roy Lewallen wrote:
Take a look at my 2005 measurements and see if you can do what Cecil and
Yuri failed to do coherently -- use the "replacement" concept and explain
where the missing degrees went.



"Cecil Moore" wrote

If you would just look at my simple stub example, you would
understand where those missing degrees are. They are at the
coil to stinger junction and may represent more than half
the degrees in the antenna. The coil represents a good portion
of the rest of the degrees. The stinger is usually about 11
degrees long.

_______________

The coil provides whatever inductive reactance is needed to make the
RADIATOR (the stinger, and mounting stub for the coil+stinger, if used)
functionally non-reactive as a system, at its feedpoint.

An 11-degree radiator/stinger doesn't radiate the power that will flow into
it any differently whether the system is resonant or not. However a
resonant system supplies more of the available source power to the stinger,
so that it CAN be radiated.

The fact that adding a coil to an 11-degree radiator produced the system
reactance a 90-degree, unloaded, linear radiator does not mean that the coil
and its junction to the stinger have supplied the "missing electrical
degrees" to the antenna system. The RADIATOR is still only 11 degrees long,
and will have same radiation resistance and relative field pattern,
regardless of the coil. The coil only supplied a non-reactive condition at
the system feedpoint.

Note that unloaded, linear radiators also can be naturally resonant at
physical/electrical lengths greater than ~90 degrees. Does that make the
same coil that can load an 11-degree stinger to resonance also responsible
for those greater "missing degrees?"

The effort spent here in bitter argument about phase shift through a coil,
and missing degrees would be better spent on methods of improving the
radiation resistance of such systems, and reducing the matching and r-f
ground losses that limit their performance.

RF