[Elecraft] Incidental AM using FSK-D

[Hank Garretson]

Keep in mind that this is one case where instrument precisipn is more
important than instrument accuracy.

73,

Hank, W6SX



On Monday, November 10, 2014, Don Wilhelm <w3fpr at embarqmail.com> wrote:

> 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.
>>>
>>>
>>>
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