[Elecraft] Poor Low audio frequency response on JT65 mode with my K3 ?

[iain macdonnell - N6ML]

Don,

JT65 spots include an offset from the center of the (2kHz) audio
passband, which is nominally centered at 1270.46Hz, so a "DF" of -500
would be at audio frequency ~770Hz, and DF-1000 would be ~270Hz.

I have a software macro for setting up for JT65, which includes
"MD6;DT0;BW0200;IS 1270;"

To give genuine JT65 signal reports, you want the full 2kHz of audio,
as the signal report is dB value relative to the "noise figure" across
that 2kHz.

73,

    ~iain / N6ML



On Tue, Nov 13, 2012 at 9:47 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
> Cliff,
>
> The K3 defaults to a 400 Hz bandwidth when selecting DATA A mode. unless
> you have previously set some other width.
>
> I am not sure about the negative bandwidth values you have indicated,
> but I am going to assume that those are just "dashes" and not negative
> signs.
>
> I suggest you look at the width and shift (or HiCut and LoCut) to obtain
> the filter bandwidth that you desire for digital modes.
>
> When working with a waterfall display, you may want a wide bandwidth,
> but if you are tuning for a single signal with the K3 VFO knob, you will
> want a more narrow bandwidth.
>
> 73,
> Don W3FPR
>
> On 11/13/2012 7:04 PM, Clifford Hynds wrote:
>> Hope someone has an answer,
>>
>> I am a recent owner of the K3 having just bought a K3, P3 and KPA500
>> station from another ham.
>>
>> Probably you would have to be a regular user of the JT65 mode to notice but
>> I seem to get little or no output when I am below about -500hz or so on the
>> waterfall on JT65HFand nothing really at -1000Hz, fine from there up.
>>
>> Probably affect other data modes also ?
>>
>> I am using line in/out on the K3 and DATA mode so no equalisation,
>>
>> Had no problems with other rigs FT847,FT817 and TS950SDX had no problems
>> with the low end.
>>
>> Could be as simple as increasing the input capacitor for the line audio or
>> as the audio is controlled by the DSP perhaps an upgraded DSP unit. The K3
>> is in the < 1000 Serial numbers 718 if i remember not in front of it at the
>> moment.
>>
>> Hope someone has an answer,
>> thanks
>> Cliff VK2CCJ
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