[Elecraft] Incidental AM using FSK-D

[Hank Garretson]

Easy. Put a decent scope on the RF envelope.

73,

Hank, W6SX



On Monday, November 10, 2014, Joe Subich, W4TV <lists at subich.com> wrote:

>
> > My K3 increases power by 10% when in Space as opposed to Mark.
>
> Two things here ...  10% is abut 0.4 dB.  How did you measure the power
> difference and did you do so with an instrument with enough resolution
> to accurately measure that difference at the power level you were using?
> For example a Bird Wattmeter can't possibly measure with that level of
> accuracy nor is one likely to be able to read an analog meter that
> closely.
>
> I have measured my K3 on RTTY with a wattmeter traceable to NIST and
> specified for 3% accuracy and have done so at four specific power
> levels (25, 55, 80 and 105 Watts) to eliminate any ALC non-linearity
> or PA compression from consideration.  The specific Mark/Space power
> levels were measured by placing the rig into transmit in FSK_D mode
> with the FSK input closed (Mark), measuring the power output for a
> given power setting, then opening the FSK input and noting the PO
> (and change).
>
> In all cases, the difference between MARK and SPACE was less than 2%
> (less than the meter's specified accuracy) and at two power levels (55
> and 80 W) the measured difference was less than 0.2W (<0.2 dB at 55W).
>
> These measurements were made with standard "High tones" (2125/2295 Hz)
> and the K3 was equipped with the optional 2.8 KHz, 8 pole IF filter.
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 2014-11-10 8:42 PM, Bill Lewis wrote:
>
>> I am looking for information on how to eliminate incidental AM when using
>> FSK-D.
>>
>> My K3 increases power by 10% when in Space as opposed to Mark.
>>
>> Thanks much, Bill, W8NN
>>
>>
>>
>>
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