How the hell an antenna may work fine with a 3:1 SWR ?
:)

On 10/24/08, Nate Duehr <nate@natetech.com> wrote:
> Sean Breheny wrote:
> > Hi Nate,
> >
> > I think I get what you are saying, but reducing power will not change
> > the SWR (since it is a ratio). I think in reality that there is some
> > threshold for reflected power that the transmitter has and above that
> > level it will cut down on the output power to get the reflected power
> > below that level.
> >
> > One thing which that article seems (in a quick skim) to fail to
> > address is that reflected power can damage a transmitter. This
> > aggressive power reduction MAY be necessary to protect the transmitter
> > output stage. It isn't intended to protect the stuff outside of the
> > transmitter (antenna, feedline, etc.) and so it would not be "better"
> > if the transmitter did not cut back. That being said, it could be that
> > some transmitters are too aggressive in doing so.
> >
> > Sean
>
> He does mention it as the reason the transmitters have that behavior,
> and that ALL modern transistor-final PA transmitters are very aggressive
> at protecting themselves.
>
> Often an antenna system that worked "just fine" at a 3:1 SWR on an old
> tube rig will fold-back power on a modern rig to the point where the guy
> on the other end can no longer copy you.
>
> The fold-back circuit can cause a much higher power "loss" overall in
> your transmitted signal than having a non-resonant antenna system.  Many
> newer hams do not understand this.
>
> His point in the article, is that you can do the math (something
> Amateurs do less and less these days... "plug and play" radio operation,
> so to speak) and prove your overall system's performance.  And the
> numbers might surprise you if you take the rig's protection circuitry
> into account.  (Something that people also rarely do.)
>
> And then if you're like me, you go MEASURE it to see if it matches
> theory, or find the reason why not.  And personally, I prefer resonant
> antennas, but if I have to work a band that just won't work with my
> antennas, I use a tuner and "make the radio happy".
>
> Nate
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