K3s AM filter

[Dave Sublette-2]

Good evening all,

I installed the 6 KHz filter into FL1 on the main receiver today.  I did
not put one in the sub receiver.  To do this, I had to move four filters
from slots 1 thru 4 to slots 2 thru 5 in both receivers. So now I have 6
KHz in FL1 in the main Rx, no filter in FL1 in the sub receiver and FL2
thru FL5 match widths in the main and sub receivers.  I made the
appropriate entries in the gain and setup menus.  Checking them on several
bands shows that all appears to be in order.

However, in the AM mode I can only widen the passband to 5.0 KHz.  Is this
normal operation, or have I missed something?

Thanks as always for your advice.

Dave, K4TO
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[Don Wilhelm]

Dave,

That is not a problem, but a result of AM modulation.

The filters work at the IF passband.
The 5kHz is the audio bandwidth.
For an AM signal, the IF bandwidth must be twice the audio bandwidth -
there are 2 sidebands, and the audio width is only equal to the width of
one sideband.

You could try synchronous AM receive.

73,
Don W3FPR

On 11/1/2019 8:27 PM, Dave Sublette wrote:

> Good evening all,
>
> I installed the 6 KHz filter into FL1 on the main receiver today.  I did
> not put one in the sub receiver.  To do this, I had to move four filters
> from slots 1 thru 4 to slots 2 thru 5 in both receivers. So now I have 6
> KHz in FL1 in the main Rx, no filter in FL1 in the sub receiver and FL2
> thru FL5 match widths in the main and sub receivers.  I made the
> appropriate entries in the gain and setup menus.  Checking them on several
> bands shows that all appears to be in order.
>
> However, in the AM mode I can only widen the passband to 5.0 KHz.  Is this
> normal operation, or have I missed something?
>

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[Bob McGraw - K4TAX]

Dave et al:

I have the 6.0 kHz AM filter in my radio.  Yes the DSP BW goes to 5
kHz.   However in using the P3 I find the total bandwidth as shown to be
about 8 kHz or +/- 4 kHz of center frequency.     In synchronous AM you
will have 4 kHz BW either USB or LSB depending the Shift setting.

73

Bob, K4TAX

On 11/1/2019 7:36 PM, Don Wilhelm wrote:

> Dave,
>
> That is not a problem, but a result of AM modulation.
>
> The filters work at the IF passband.
> The 5kHz is the audio bandwidth.
> For an AM signal, the IF bandwidth must be twice the audio bandwidth -
> there are 2 sidebands, and the audio width is only equal to the width
> of one sideband.
>
> You could try synchronous AM receive.
>
> 73,
> Don W3FPR
>
> On 11/1/2019 8:27 PM, Dave Sublette wrote:
>> Good evening all,
>>
>> I installed the 6 KHz filter into FL1 on the main receiver today.  I did
>> not put one in the sub receiver.  To do this, I had to move four filters
>> from slots 1 thru 4 to slots 2 thru 5 in both receivers. So now I have 6
>> KHz in FL1 in the main Rx, no filter in FL1 in the sub receiver and FL2
>> thru FL5 match widths in the main and sub receivers.  I made the
>> appropriate entries in the gain and setup menus.  Checking them on
>> several
>> bands shows that all appears to be in order.
>>
>> However, in the AM mode I can only widen the passband to 5.0 KHz.  Is
>> this
>> normal operation, or have I missed something?
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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