[Elecraft] MMTTY DATA-A or FSK

[Joe Subich, W4TV]

On 2014-10-02 12:03 PM, dmoes at nexicom.net wrote:>
 >
> Joe you are correct that if there are physical problems and poor
> adjustments it will be bad but I was assuming a good working setup
> with a quality sound card that is properly adjusted at both the
> computer and K3 that it will be fine.

Unfortunately, that is not a good assumption.  Even the best of
stations with *professional* operators and maintenance can have
adjustment problems or equipment failures (I've documented such
even at W1AW in the last couple years).  When you add in the
relative inexperience of someone new at sound card based digital
modes, conditions become very bad very quickly and I can provide
example after example of maladjusted rigs, improperly operating
home brew interfaces, etc.

At least, by placing a narrow filter in the transmit audio path,
the K3 prevents the greatest number of those errors.  Other rigs
with no monitor, no audio controls, ineffective ALC, and no audio
filtering become QRM generators if one looks at them cross-eyed.

73,

    ... Joe, W4TV


On 2014-10-02 12:03 PM, dmoes at nexicom.net wrote:
>
>
> Joe  you are correct that if there are physical problems and poor
> adjustments it will be bad  but I was assuming a good working setup with
> a quality sound card that is properly adjusted at both the computer and
> K3 that it will be fine.
>
>     I hope that they add the ability to monitor Transmit signal on the
> P3 to see how it looks going out.  however you can see your real signal
> by watching your signal on the many online SDR's, http://websdr.org/,
> that have waterfall displays in real time.
>
>
> David Moes
> VE3DVY
>
>
> On Thursday 02/10/2014 at 9:01 am, "Joe Subich, W4TV"  wrote:
>>
>>>
>>> risk is any off frequency noise from the sound card, harmonics etc
>>> will also get transmitted not really a big issue if the sound card is
>>> good quality.
>>
>> Not quite accurate ... one can have a professional quality sound card
>> and if the levels are too high, the connections are not correct, the
>> ground gets opened, one has a significant degree of common mode RF on
>> the feedline, one has power supply issues, etc. DATA_A can be very
>> badly distorted/wide.  AFSK A is not subject to those issues as long
>> as the narrow filter (CONFIG: AFSK TX) is enabled.
>>
>> 73,
>>
>>        ... Joe, W4TV
>>
>>
>> On 2014-10-02 7:30 AM, david Moes wrote:
>>>
>>> With AFSK-A  the K3  has very a narrow DSP filter to maintain a really
>>> good transmit IMD  so you need to keep the modulating frequencies
>>> within  the chosen preset filter range  1275 in my setup.  You can use
>>> the waterfall to tune but you need to use DATA-A instead of AFSK-A risk
>>> is any off frequency noise from the sound card, harmonics etc will also
>>> get transmitted   not really a big issue if the sound card is good
>>> quality.   I found that with the P3 the markers lined up with the mark
>>> frequency  so tuning with the VFO was quite convenient without the P3 I
>>> may have been more tempted to use Data-A and tuning with the mouse
>>>
>>> David Moes
>>> President: Peterborough Amateur Radio Club.
>>> dmoes at nexicom.net
>>> VE3DVY,  VE3SD
>>>
>>> On 10/2/2014 06:32, David Cole wrote:
>>>>
>>>> Why only tune the radio, and not use the Waterfall?
>>>
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