[Elecraft] K3s SSB transmitting bandwidth?

[Joe Subich, W4TV]

On 2018-12-25 11:54 AM, Michael Blake via Elecraft wrote:
 > Thanks Don.  The published curves ( 
https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves 
) suggest
 > that there will be significant low end rolloff below 300 Hz.

The actual low end is controlled by two parameters: the low cut
frequency in the DSP algorithm and the local oscillator frequency
(where the IF filter is placed relative to the carrier frequency).

In general, the "normal" passband for a 2.7 KHz SSB signal would
be 300 - 3000 Hz.  In the K3/K3s that bandpass would primarily be
set by the DSP.  In fact, if you look closely at the response of
both the 2700 and 2800 Hz filters you will notice they are not
symmetrical - they have steeper skirts on the high frequency side
than the low frequency side.  If the filter were the only determinant
of transmit audio response, one sideband would have less low end
response than the other.

In analog filter SSB designs, one typically set the carrier at -40 dB
on the filter skirt (to improve carrier suppression) and accepted the
low frequency roll off that started between 200 and 500 Hz (depending
on the filter skirts).   For the K3/K3S, I'm certain that Elecraft
adjust the "carrier offset" to some degree for normal SSB and ESSB
settings but I don't recall ever seeing response specifications
other than total bandwidth (2.7, 3.0., 3.1, 3.2, 3.2, 3.4, 3.5, 3.6,
3.7, 3.8, 3.9 and 4.0 KHz).

73,

    ... Joe, W4TV


On 2018-12-25 11:54 AM, Michael Blake via Elecraft wrote:
> Thanks Don.  The published curves ( https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves <https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves> ) suggest that there will be significant low end rolloff below 300 Hz. But I have not taken the time or effort to attempt to measure it myself.  I believe that the ESSB improvements also require a wider filter to be totally effective.
> 
> The reason I ask is that when on-the-air testing of my new HyperX Cloud Pro headset there was not much change (none actually) noticed when I rolled 50Hz. And 100Hz. off to -16.
> 
> I thought that I had seen actually measurements of the actual rolloff in the past and thought that someone might recall where there were.
> 
> Very 73 - Mike - K9JRI
> 
> 
>> On Dec 25, 2018, at 11:18 AM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>>
>> Michael,
>>
>> I think the rolloff is not much (in support of those who want ESSB operation.  Much of the rolloff depends on your microphone.
>> Jim Brown K9YC has long advocated reducing the TX EQ below 500 Hz or so in order to increase your effective communications power.  An improvement of 3 dB or more can be had by reducing the low frequency audio since those low frequencies take a lot of the total power and add little to communications effectiveness.
>>
>> 73 and Merry Christmas,
>> Don W3FPR
>>
>> On 12/25/2018 11:03 AM, Michael Blake via Elecraft wrote:
>>> When using the stock K3s 2.7 KHz. roofing filter and all TX EQ settings are zero (0) what is the normal TX audio rolloff below 300Hz.?
>