The only thing that high swr on a yagi should tell you is that the feed line
does not match the driven element impedance perfectly.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Gary Smith
> Sent: Friday, April 24, 2009 12:02 PM
> To: amps@contesting.com
> 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@contesting.com
> Sent: Thursday, April 23, 2009 9:26 AM
> Subject: Re: [Amps] High SWR
>
>
>
>
> > -----Original Message-----
> > From: amps-bounces@contesting.com [mailto:amps-bounces@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
>
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