[Amps] High SWR

[jmltinc at aol.com]

Carl, if you are refering to poor F/B; I think you are quite correct on this point. Common-mode currents would radiate. You would then have Yagi and a vertical antenna which would degrade the directivity.

-John, N9RF


-----Original Message-----
From: Carl <km1h at jeremy.mv.com>
To: Gary Smith <wa6fgi at sbcglobal.net>; amps at contesting.com
Sent: Fri, 24 Apr 2009 11:44 am
Subject: Re: [Amps] High SWR



<SNIP>
Another reason would be feedline radiation which can be minimized with a 
good sleeve balun as described everywhere for decades.

Carl
KM1H


----- Original Message ----- 
From: "Gary Smith" <wa6fgi at sbcglobal.net>
To: <amps at contesting.com>
Sent: Friday, April 24, 2009 12:02 PM
Subject: Re: [Amps] High SWR


>A comment: I have been told that a high swr on a yagi antenna reduces 
>the front to back ratio.  Any truth (facts?) to support this info?
> 73,
> Gary...wa6fgi
>  ----- Original Message ----- 
>  From: Gary Schafer
>  To: 'Scott McGrath' ; amps at contesting.com
>  Sent: Thursday, April 23, 2009 9:26 AM
>  Subject: Re: [Amps] High SWR
>
>
>
>
>  > -----Original Message-----
>  > From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On
>  > Behalf Of Scott McGrath
>
>  > In reality and especially with a tube amplifier and a Pi output 
> tank the
>  > antenna system can be brought into resonance at a wide range of
>  > impedances and resonance is what we are looking for and it really 
> is
>  > Antenna System Goodness in MOST cases.    As the reflected power is
>  > definitely real but it is best expressed as the reactive power in a
>  > system which effectively is lost.   With ladder line if long enough 
> will
>  > re-radiate some of this 'lost' power.
>
>  Reflected power is not best expressed as reactive power. It is real 
> power
>  and it is not lost power just because it is reflected. when reflected 
> power
>  sees the matching network in the final amp or antenna tuner it then 
> gets
>  re-reflected back toward the antenna to be ultimately radiated along 
> with
>  the rest of the power. The only "lost power" is that due to the feed 
> line
>  loss on both the forward and reflected power.
>
>  With ladder line the loss is normally very low and very little 
> forward power
>  is lost and very little reflected power is lost. There can be very 
> high swr
>  (high reflected power) on the line and most all of the reflected 
> power will
>  end up getting back to the antenna to be 
radiated by the antenna.
>
>  Ladder line will not re_radiate reflected power any more than it will
>  radiate forward power. If the line is well balanced it will not 
> radiate
>  either forward or reflected power that may be on it.
>
>  73
>  Gary  K4FMX
>
>  _______________________________________________
>  Amps mailing list
>  Amps at contesting.com
>  http://lists.contesting.com/mailman/listinfo/amps
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps 

_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps