[Premium-Rx] Radios and High RF powers

[J. Forster]

As I remember, in a WG below cutoff the attenuation (in db) is proportional to
the distance down the guide in wavelengths. The  two important parameters are
the ratio of (signal wavelength)  /  (cutoff wavelength)   and the ratio of
(distance down guide) / (guide wavelength).  Those two ratios define the
attenuation. I can look up the formula if anyone really needs it.
-John


George Georgevits wrote:

> John,
>
> There must be more to it than that - something about the length of the pipe
> vs wavelength it is trying to filter out. I seem to recall from my Uni days
> way back that if you want something to act as a transmission line (and
> presumably this applies to waveguides as well) then it must be a significant
> fraction of the wavelength you are working with. Otherwise, it acts like a
> lumped element. In other words, six inches of pipe would look like a very
> small feedthru capacitor? Perhaps someone can enlighten me here?
>
> Given the above, 8uS rise time corresponds to something like 75KHz, and the
> wavelength is VERY long. You would need a lot of pipe?
>
> Regards,
> George Georgevits
> Power and Digital Instruments Pty Ltd
>
> -----Original Message-----
> From: premium-rx-bounces at ml.skirrow.org
> [mailto:premium-rx-bounces at ml.skirrow.org]On Behalf Of J. Forster
> Sent: Tuesday, 3 June 2003 7:44 AM
> To: George Georgevits
> Cc: larry at gadallah.com; premium-rx at ml.skirrow.org
> Subject: Re: [Premium-Rx] Radios and High RF powers
>
> That's why a WG below cutoff works. If it had a risetime of less than a
> nanosecond, it would have lots of GHz stuff that'd go right through a pipe a
> inch or two in diameter.
> -John
>
> George Georgevits wrote:
>
> > Guys,
> >
> > The standard impulse shape used to simulate lightning surges in cable has
> 8
> > microsecond rise time (10% to 90% of peak value) and 40 microsecond fall
> > time to half value - hardly microwave stuff!
> >
> > Regards,
> > George Georgevits
> > Power and Digital Instruments Pty Ltd
> >
>
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