[TowerTalk] Reflections, Tuners and Antenna Forum Talks

[Michael Tope]

Hi Tom,

Yes, you are correct that with our 3 KHz wide SSB signals, we can
ignore the transient response of the transmission line. I was just
responding to to Jim comments on what Steve had said about
the initial load conditions on the tuner.

I really can't comment much further because I haven't sorted thru
the entirety of Steve and Walts postings, although I must say I
am confused by the idea of virtual shorts and opens when looking
back toward the source.  I will keep reading this weekend
though.

73 de Mike, W4EF..........


----- Original Message -----
From: Tom Rauch <w8ji@contesting.com>
To: Jim Reid <kh7m@hsa-kauai.net>; Steven Best <sbest@cushcraft.com>;
<towertalk@contesting.com>; Michael Tope <w4ef@pacbell.net>
Sent: Friday, May 12, 2000 5:22 AM
Subject: Re: [TowerTalk] Reflections, Tuners and Antenna Forum Talks


>
> Hi Mike,
>
> I swore I wasn't going to get into one of these threads, but...
> >
> > transmission line transformer. The drawing shows how the multiple
> > reflections of the incident energy add up to form the steady state
> > solution for the 1/4 wave line (matched condition). The following page
> > shows the time progression for a short pulse along the same 1/4 wave
line.
> > Kraus states "It is clear that the transformer fails to function as a
> > reflectionless device for a pulse as short as indicated.........".
>
> I'm not sure where any of you are going with this stuff.
>
> It's true you can't consider the system in a steady state condition
> with a wide-bandwidth very fast rise-time transmission, but we sure
> can with a narrow-band signal like one of our HF transmitters,
> especially with the length of transmission lines we deal with. The
> rise time is very slow, it takes many many RF cycles to build
> power no matter what operating or mode frequency we are using.
>
> There is nothing I can find where Maxwell claims a system is
> matched under transient conditions, and if I follow his reasoning it
> is obvious the system would not be matched under transient
> conditions. As you say that is why television transmitters, or any
> other system having fast information rate changes compared to the
> delay in the transmission line, requires a nearly perfect VSWR.
>
> So I say, big deal. Wave mechanics work just fine. They ALSO
> explain why high load VSWR isn't acceptable in a system where
> the time delay in the transmission line approaches the information
> rate change in the transmitter.
>
>
> 73, Tom W8JI
> w8ji@contesting.com
>
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