K3: Passband tuning questions

[VK5ABQ]

I don't understand some functionality of the K3's passband tuning. If I select AM, and activate NORM then Fc=1.50KHz(an asterisk is alongside this figure on the display). Since the selected roofing filter defaults to 6KHz I figure the displayed value of Fc is the centre frequency of the audio bandwidth, not the RF bandwidth. So the bandwidth control refers to RF bandwidth and the Fc control refers to audio bandwidth?

Next if I widen the bandwidth to 10.00KHz (allowing the K3 smarts to select the 12KHz roofing filter automatically) and then switch to HI/LO CUT, the LO figure displayed is 0.00 and the HI figure is 4.20 (again, audio frequency figures I assume?), doesn't this mean the current RF bandwidth is 8.4KHz? What happened to 10KHz? Shouldn't LO=0 (or more like 0.25 due to the DSP's alleged audio attenuation) and HI=5.0?

Thanks. I'm going through a whinge period at the moment - bah humbug!

[VK5ABQ]

Sorry I made a mistake above. Where I typed 4.20KHz should be 4.00KHz.

Why the lack of replies? Isn't the passband tuning faulty?

Set the K3 to AM
Set Bandwidth to 10KHz
Set Fc to 1.50KHz
Switch to HI/LO cut and discover HI=4.00KHz and LO=0.00KHz. Shouldn't HI=5.00KHz if bandwidth is set to 10KHz?

Thanks.

[Don Wilhelm-4]

Shane,

Because 4.00 kHz is as high as it goes at the moment.
High Fidelity short wave listening is not the major focus of the K3, the
priority functions are communications related.

73,
Don W3FPR

VK5ABQ wrote:

> Sorry I made a mistake above. Where I typed 4.20KHz should be 4.00KHz.
>
> Why the lack of replies? Isn't the passband tuning faulty?
>
> Set the K3 to AM
> Set Bandwidth to 10KHz
> Set Fc to 1.50KHz
> Switch to HI/LO cut and discover HI=4.00KHz and LO=0.00KHz. Shouldn't
> HI=5.00KHz if bandwidth is set to 10KHz?
>
> Thanks.
>
> -----
>
> Shane
>  
>  

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[Joe Planisky]

Hi Shane,

There are indeed several oddities with the DSP filtering (passband  
tuning), particularly related to switching from CENTER/WIDTH mode to  
LO/HI CUT mode.  I posted my findings on Nov. 26, 08 in the message  
with the subject line "LO CUT/HI CUT Bugs?"  Lyle acknowledged the  
message and said it was on the list to be corrected.


73
--
Joe KB8AP

On Dec 13, 2008, at 3:02 AM, VK5ABQ wrote:

>
> Sorry I made a mistake above. Where I typed 4.20KHz should be 4.00KHz.
>
> Why the lack of replies? Isn't the passband tuning faulty?
>
>
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[VK5ABQ]

Ah OK then. I had noticed some other strange behaviour by the passband graphics too.
Thanks Joe. It IS nice to know Elecraft are keen to continue improving the K3.

Joe Planisky wrote

Hi Shane,

There are indeed several oddities with the DSP filtering (passband  
tuning), particularly related to switching from CENTER/WIDTH mode to  
LO/HI CUT mode.  I posted my findings on Nov. 26, 08 in the message  
with the subject line "LO CUT/HI CUT Bugs?"  Lyle acknowledged the  
message and said it was on the list to be corrected.


73
--
Joe KB8AP

On Dec 13, 2008, at 3:02 AM, VK5ABQ wrote:

>
> Sorry I made a mistake above. Where I typed 4.20KHz should be 4.00KHz.
>
> Why the lack of replies? Isn't the passband tuning faulty?
>
>
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