Fw: New 3.41 IMPROVED RX LOW-FREQUENCY RESPONSE in AM/SSB/CW MODES

[mark roz]

Went back to 3.30 and LOW FREQ resp. is about the same.
Anybody else?
--- On Tue, 10/6/09, mark roz <[hidden email]> wrote:


From: mark roz <[hidden email]>
Subject: New 3.41 IMPROVED RX LOW-FREQUENCY RESPONSE in AM/SSB/CW MODES
To: "Elecraft" <[hidden email]>
Date: Tuesday, October 6, 2009, 5:15 PM







K3 set to DSP width 4kHz and I'm using very good headphones.
No difference with low freq. response.
What is the problem?
Mark 



     
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[TomB W1PKX]

mark roz wrote

Went back to 3.30 and LOW FREQ resp. is about the same.
Anybody else?
--- On Tue, 10/6/09, mark roz <[e-mail]> wrote:


From: mark roz <[e-mail]>
Subject: New 3.41 IMPROVED RX LOW-FREQUENCY RESPONSE in AM/SSB/CW MODES
To: "Elecraft" <[e-mail]>
Date: Tuesday, October 6, 2009, 5:15 PM







K3 set to DSP width 4kHz and I'm using very good headphones.
No difference with low freq. response.
What is the problem?
Mark 



     
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[TomB W1PKX]

In AM receive I don't see any difference with previous (3.30) release. The 50 Hz RX EQ slider has no effect as before. I haven't measured it, but the Low cutoff still seems to be ~100 Hz.

I notice in AM, with SHIFT=1.50,LO=0.00and width=5.00 the HI shows 4 Khz. I don't understand that. If I set SHIFT=1.7 then the HI goes to 4.2 Khz. In AM I have the FM filter selected.


Tom

mark roz wrote

Went back to 3.30 and LOW FREQ resp. is about the same.
Anybody else?
--- On Tue, 10/6/09, mark roz <[e-mail]> wrote:


From: mark roz <[e-mail]>
Subject: New 3.41 IMPROVED RX LOW-FREQUENCY RESPONSE in AM/SSB/CW MODES
To: "Elecraft" <[e-mail]>
Date: Tuesday, October 6, 2009, 5:15 PM







K3 set to DSP width 4kHz and I'm using very good headphones.
No difference with low freq. response.
What is the problem?
Mark 



     
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[Dick Dickinson]

Shift + Width/2 = High


Best regards,

Dick - KA5KKT

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[TomB W1PKX]

Thanks Dick,

I can see "Shift + Width/2 = High" is true for SSB, but not for AM (i.e. double sideband).

It is not obvious why in AM the HI cut is 1 Khz less than the Width. There is no setting of SHIFT/WIDTH/LO which indicates HI = 5 Khz.

I was under the assumption a 5 Khz width implied +/- 5 Khz from the carrier which implies the highest AF component is 5Khz.

What does the "nominal" shift =1.5 imply for AM ? I would think, nominally, the roofing and DSP filters would be capable of zero shift (i.e., centered on the carrier) in AM.

To me, the WIDTH,SHIFT and HI values are inconsistent for AM.

Tnx

Tom

Edward Dickinson, III-2 wrote

Shift + Width/2 = High


Best regards,

Dick - KA5KKT

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[Don Wilhelm-4]

Tom,

For AM, the K3 shows the audio channel width, not the IF width.
Add to that, the upper audio frequency on the K3 is limited to about 4 kHz.
The IF width of an AM signal is twice the audio channel width.  In other
words, reception of AM with a 4 kHz audio channel requires an IF channel
at least 8 kHz wide.
You are getting more with the FM filter than you would with the 6 kHz AM
filter - if you were using the 6 kHz filter the audio bandwidth would be
constrained to about 3 kHz even though you could set the DSP high
frequency to 4 kHz.

You may have to increase the value of the coupling capacitors in the
audio output of the K3 to hear the lower bass response better.

73,
Don W3FPR

TomB W1PKX wrote:

> In AM receive I don't see any difference with previous (3.30) release. The
> 50 Hz RX EQ slider has no effect as before. I haven't measured it, but the
> Low cutoff still seems to be ~100 Hz.
>
> I notice in AM, with SHIFT=1.50,LO=0.00and width=5.00 the HI shows 4 Khz. I
> don't understand that. If I set SHIFT=1.7 then the HI goes to 4.2 Khz. In AM
> I have the FM filter selected.
>
>
> Tom
>  
>

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