[Elecraft] Incidental AM using FSK-D

[Phil Wheeler]

As a practical matter "My K3 increases power by 
10% when in Space as opposed to Mark": is this 
really something to be concerned about?

Phil W7OX

On 11/10/14 10:51 PM, Brian wrote:
> And what if this was done this with the standard 
> 2.7 KHz filter? Filter passband ripple has the 
> the stock answer to what people are observing.
>
> Also what about dynamic vs static differences.  
> Is it possible in the dynamic situation the 
> differences would be greater?
>
> It does sound like there is some confusion 
> precision with accuracy.  A measuring device 
> might offer high precision and resolution but 
> lower absolute accuracy.  People often make 
> accurate difference measurements with with a 
> device which less accurate than the delta one 
> observes.  If the difference are small, they can 
> be quite accurate.
>
> 73 de Brian/K3KO
>
>
> On 11/11/2014 02:13, Joe Subich, W4TV 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