[Elecraft] Incidental AM using FSK-D

[Don Wilhelm]

Not so easy even with a decent scope.
50 watts will produce 141.42 volts p-p, and 55 watts will produce 148.32 
vp-p.
That is a difference on 7.1 vp-p for a 10% difference in power.
That small difference is difficult to discern on a scope at that 
vertical amplitude.
Yes, a small difference in amplitude can be discerned, but to quantify 
it to less than a 5% difference is difficult to measure with a 'scope.

73,
Don W3FPR

On 11/10/2014 9:23 PM, Hank Garretson wrote:
> 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.
>>
>>