[Elecraft] Re: Displaying the keying waveshape on Spectrogram.

Fri Sep 12 02:19:00 2003

Nice plot. Try it on an unmodified FT1000MP...

Probably should set the received tone to 1250 so you get to see both
sides down to the bottom. Though I'm surprised how far out you can
detect the signal. I'm betting all of the stuff beyond 250 or 300 goes
away when Wayne gets done.

Also the K2 is symmetrical so it's likely all waveshaping. The MP's is
NOT symmetrical, possibly due to the keying coming on just a tiny tad
before all the frequency generation is settled down from the state
change.

Won't pegging the interference to the CENTER of the adjacent channel
cause the stated figure to seem better than the interference really
is? 10 db better in this case?

A Collins 500 Hz mechanical filter is rated by their method as being
down THREE db at the indicated points and dropping more rapidly after
that. Other manufacturers use -6 dB points. and then most modern
filters are quite level inside the passband. So certainly by the time
you go past +/- 300 Hz, the other guy, using a 500 Hz filter, is
hearing you full strength.

Many a decent receiver will be bothered by the clicks at the level
measured +/- 250, not +/- 500 Hz. So the figure you should QUOTE for
that particular K2 is -40 db +/- 250 Hz. Or stated another way, this
signal will pump the other fella's fast attack slow decay AGC a lot
more like -40 than -50.

Use property owners grass cutting rules for this. One inch on that
side of the line, he mows it 3 inches high, one inch this side I mow
it 4 inches high. I own +/- 249 Hz, they own +/- 251 Hz.

If that Texas 40 over nine signal is using this, the clicks are S9 in
the adjacent channel.

However, if the carrier is only S6, the clicks would be in the noise.

I see you have a different scale, and I just checked my Spectrogram,
and I have v. 7.2. Now that I recall, there was an upgrade notice
which I forgot about, so guess I should go download it.

73, Guy.

----- Original Message ----- 
From: "Dale Boresz" <[email protected]>
To: <[email protected]>
Sent: Friday, September 12, 2003 12:08 AM
Subject: [Elecraft] Re: Displaying the keying waveshape on
Spectrogram.

> After reading Guy's (K2AV) excellent explanation of measuring the
K2's
> keying waveform with Spectrogram, I decided to measure my own K2,
using
> the ICOM IC-746PRO as the monitoring receiver.
>
> The Spectrogram plot of the results can be viewed at:
> http://64.105.107.250/kqrv/k2keying.aspx
>
> 73, Dale - wa8sra
>
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