Re: [Elecraft_K3] P3 Signal presentation on the screen

Mel Farrer <farrerfolks@...>

Thanks Alan,

That explains a lot.  I will look at the schematic of the SM-230 and see what the video filter is like.  Interesting problem. 

Mel, K6KBE

From: Alan Bloom To: Elecraft_K3@...
Sent: Wed, November 17, 2010 10:29:27 AM
Subject: Re: [Elecraft_K3] P3 Signal presentation on the screen


The concept of rise and fall time does not really apply to a device like
the P3 that uses an FFT (Fast Fourier Transform) to generate the
frequency spectrum.

In a traditional analog swept-frequency spectrum analyzer, there is a
separate "resolution bandwidth" filter at the IF and a "video" filter
that is after the detector. The video filter could have different rise
and fall times, depending on its design.

The resolution bandwidth determines the minimum distance between two
signals that can be resolved on the display. In the P3 the effective
resolution bandwidth is basically one display pixel (span / 450),
bottoming out at about 7 or 8 Hz at the narrowest spans. There is no
separate video filter.

Alan N1AL

On Wed, 2010-11-17 at 00:55 +0000, farrerfolks wrote:
> I have a question. Are the signals on the display symmetrical rise
> time and decay time? That is a real problem on the Kenwood station
> monitors with band scan. They have a fast rise time, but distorted and
> wide fall time. Comments appreciated.
> Mel, K6KBE

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