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> From: Jim Bradshaw <ac6tk@cybertime.net>
> To: towertalk@contesting.com
> Subject: [TowerTalk] Re: Impact of Reflected Power
To: <towertalk@contesting.com>
> Date: Wednesday, July 29, 1998 7:39 PM
>
Sri Folkes,
I was in error on the first 2 lines of my incursion of bandwidth. Haste
can do that.
I thank Jim Ried for vehemently calling this to my attention. Of course
this could not be hapenning at "multiples" of the speed of light. I was
confusing speed with time. I meant to imply that with propagation at/near
the speed of light, the distortion caused by the delay of several
reflections would not be great enough when compared to distortions in
ionospheric propagation, to be heard. SWR need not be an excuse to be off
of the air as long as we can make the transmitter happy and keep losses to
a minimum.
Unfortunately due to my schedule I don't get a chance to hang on every
message as it comes in so I didn't get a chance to participate in real
time. It was nice to see that so many respondants had a real grasp of SWR
and its true consequences.
>
X Consider that if these reflections are hapenning at the speed of light
X (small multiples of). The echo or delay will be unnoticeable on SSB or
CW
> especially when dealing with atmospheric conditions that will certainly
> introduce more noticable distortions.
>
> Fast scan Television is another story because the modulation technique is
> highly sensitive to distortions of the phase relationships. Ghosting
> results.
>
> For SSB & CW, the distorted waveshape that results from reflections will
> still energize the antenna and produce the electromagnetic field.
>
> So the questions remaining are; how much more loss is incurred in all
that
> makes
> up the transmission line including tuner, balun and connectors and how
> much power is the transmitter able to make? These are valid points
because
> if the transmitter is unable to make full power, it won't be there to
lose.
> And even though out of phase relationships of the incident to reflected
> waves can't cancel out the power, they will cause higher peak values of
> both voltage and current that can increase losses.
>
>
> Jim Bradshaw, AC6TK
>
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