THESE issues are exactly why I took two months in the
summer of 2003 to make careful measurements before re-doing
my beverages. The impedance into the transformer was exactly
400 ohms ... a W8JI transformer with a pad between it and
the receiver to stabilize the input impedance of the
receiver. The point here is that if the signal goes down by
20 db. when the beverage wire is disconnected, then that
level represents the minimum level of signal that will be
picked up by the vertical feed. So if someone is trying to
null a signal or noise by more than 20 db. this is a major
factor.>>>
OK I think. Let me try to be a bit clearer John.
You saw 20dB of difference at ground level. But ground level
isn't the peak response of the Beverage, is it?
Wouldn't we have to know the difference between the absolute
peak response of the Beverage at desired wave angles to the
response of the downlead to get a rough idea of how the
downlead affects F/B (or more correctly F/R) at useful
angles?
Or am I missing something?
I know the response of a low center tapped half wave wire to
vertical signals is only down about 3 or 4 dB from the six
foot vertical wire at low and moderate angles. This is why
I'm trying to understand the big change in F/R. Maybe the T
termination moves the unwanted response from the rear to the
sides?
73 Tom
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|