[Elecraft] K3s AM filter

Bob McGraw K4TAX rmcgraw at blomand.net
Fri Nov 1 20:54:31 EDT 2019


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?
>>
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