> With the 6kHz filter it was not possible to set bandwidth 
> greater than 2.8kHz and/or Hi/lo cut to 3000Hz and 200Hz 
> using the knobs.  

That's correct.  AM is a double sideband mode and requires 
equal bandwidth above and below the carrier.  Thus with a 
6 KHz filter, one would be limited to a 3 KHz (or slightly 
more depending on the filter skirts) maximum audio frequency.  

> It might become confusing when one wants to shift the filter 
> to listen mainly to one side band; On a clear channel with 
> say 4kHz or when avoiding interference with 2kHz.

Receiving double sideband AM with offset tuning has some 
unique audio equalization requirements since the low audio 
frequencies are boosted by 6dB due to the partial remaining 
sideband. 

Lyle, it might be worth considering a higher high cut/wider 
bandwidth for receive with offset tuning.  If I recall, many 
of the SW broadcasters are using a "compatible" modulation 
that is essentially USB with a reduced (-6dB) carrier.  In 
fact, it might even be worth considering "compatible AM" 
(VSB or SSB with reduced carrier) transmit - after all it's 
only programming <G>. 

73, 

   ... Joe, W4TV 
 


> -----Original Message-----
> From: [EMAIL PROTECTED] 
> [mailto:[EMAIL PROTECTED] On Behalf Of Toby Deinhardt
> Sent: Sunday, December 16, 2007 2:44 AM
> To: Lyle Johnson
> Cc: elecraft@mailman.qth.net; DaleJ
> Subject: Re: [Elecraft] New K3 F/W - MCU: V 1.49 DSP: V 1.46 
> NR Improved.AMadded
> 
> 
> Hallo Lyle,
> 
>  > With the 6 kHz roofing filter, you should be able to set HI CUT to
>  > 3 kHz in AM mode.
> 
> I do not have my radio here, so from memory:
> 
> With the 6kHz filter it was not possible to set bandwidth 
> greater than 
> 2.8kHz and/or Hi/lo cut to 3000Hz and 200Hz using the knobs. 
> Using the 
> XFIL button 6kHz appeared to be reachable but no bandwidth 
> between 6kHz 
> and 2.8kHz.
> 
> If the 3kHz you mention is equal to 6kHz RF bandwidth (is 
> equal to 3kHz 
> AF bandwidth?), then I would suggest displaying the RF and not the AF 
> bandwidth. It might become confusing when one wants to shift 
> the filter 
> to listen mainly to one side band; On a clear channel with 
> say 4kHz or 
> when avoiding interference with 2kHz.
> 
> vy 73 de toby
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