[Fwd: Re: SHIFT pitch]

[Don Wilhelm-4]

Hi everyone,

Lyle reminded me that the K3's built-in  AF voltmeter display can be
used as a reliable indicator of audio amplitude - it is a true RMS
reading indication.  He also indicated that a steady carrier can easily
be used rather than the wideband noise source.  If you use an on-the-air
signal, be careful not to confuse amplitude changes caused by the filter
with QSB on the signal.  A QRP transmitter feeding a dummy load would
probably serve as a steady source of carrier if you do not have a signal
generator available.

There are several ways to do a relative gain evaluation, and I mentioned
only the way I am more used to using - I just didn't think of the others
initially.

73,
Don W3FPR

-------- Original Message --------
Subject: Re: [Elecraft] SHIFT pitch
Date: Tue, 27 Jan 2009 11:06:20 -0500
From: Don Wilhelm <[hidden email]>
Reply-To: [hidden email]
To: W5UN <[hidden email]>
CC: [hidden email]
References: <[hidden email]>



I suspect that the filter gain rather than the width is the major cause
of that behavior.
Try working with the FLx GN setting in the CONFIG menu to see if you can
obtain a smoother transition.
You could expect the widest filter to have the smallest loss, so start
with the transition between FL1 and FL2 and when that seems right, move
on to the FL2 and FL2 transition, etc.

The easiest way to do this is with a broadband noise generator (such as
the Elecraft NGen) so you have a constant input to the K3 and it would
be easy to evaluate the audio level using Spectrogram or some other
audio spectrum analyzer, although a AC DMM connected across the speaker
would give decent results.

Once you have the filter gains equalized, you can easily change the
filter offsets if necessary.  While the 8 pole filter offsets are close
to zero, it is not practical to expect that  they are all exactly zero.

73,
Don W3FPR

W5UN wrote:

> I have three 8 pole filters installed, 2.8, 1.8, and .4 kHz. As I
> rotate the WIDTH knob, the filters switch in and out at their
> transition frequencies (as they should). But when that switch occurs,
> the background noise pitch frequency seems to jump to a different
> SHIFT frequency setting.  In other words, the transition between
> filters is not smooth.
>
> I am wondering if all K3's with 8 pole filters do the same thing as mine?
>
> My filter offsets are all set to zero, as that is what I am told the
> 8 pole filters offsets should be.
>  
>

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[Bill Johnson-9]

Don, where do I find the AF voltmeter display?


73,

Bill
K9YEQ
K2 #35; KX1 #35; K3 #1744; mini mods


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Wilhelm
Sent: Tuesday, January 27, 2009 1:17 PM
To: 'Elecraft'
Subject: [Elecraft] [Fwd: Re: SHIFT pitch]

Hi everyone,

Lyle reminded me that the K3's built-in  AF voltmeter display can be
used as a reliable indicator of audio amplitude - it is a true RMS
reading indication.  He also indicated that a steady carrier can easily
be used rather than the wideband noise source.  If you use an on-the-air
signal, be careful not to confuse amplitude changes caused by the filter
with QSB on the signal.  A QRP transmitter feeding a dummy load would
probably serve as a steady source of carrier if you do not have a signal
generator available.

There are several ways to do a relative gain evaluation, and I mentioned
only the way I am more used to using - I just didn't think of the others
initially.

73,
Don W3FPR

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[KK7P]

> Don, where do I find the AF voltmeter display?

Please see the VFO B Alternate Displays section of the Owner's Manual.

73,

Lyle KK7P
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