http://elecraft.85.s1.nabble.com/Amplitude-variation-on-K3S-with-JT65B-tp7665870p7665875.html
Fake It keeps the tones between 1500-2000 Hz. (not 1000) so that the
> Conrad,
>
> My friend just had the issue you described with a different brand radio. He was transmitting near the high end of the TX filter and on higher tones of the FT8 the power would drop causing the TX power to waiver.
>
> The fix for him was to enable Fake It in the WSJT-X radio settings tab. That keeps the TX audio centered between 1 kHz and 2 kHz. Well within the TX filter bandwidth.
>
> Dave wo2x
>
> Sent from my waxed string and tin cans.
>
>> On Oct 21, 2020, at 7:51 AM, Conrad PA5Y <
[hidden email]> wrote:
>>
>> Hello while I wait for feedback from the (no doubt overwhelmed) Elecraft support I thought that I would ask the group about a problem that I have with my K3S.
>>
>> When I run JT65B and even to a lesser extent FT8 I see unacceptable amplitude variation on both the 6m output and the transverter output (on 28MHz). If I put my E4406 Spectrum analyser on peak hold with a narrow span and 10Hz RBW I see amplitude variations of a little over 1dB on the modulation tones across the passband.
>>
>> To save time.
>>
>>
>> 1. On the ALC meter I have 4 bars lit up with the 5th occasionally flickering - the audio drive level is correct; it is not an ALC issue
>> 2. I calibrated the TX drive - the effect is observed at 1mw, 5W, 50W and 100W on 6m.
>> 3. I am using DATA A so no TX EQ or compression
>> 4. The audio has from WSJT-X been measured on a UPV audio analyser and there is less than 0.1dB variation when using a UMC404HD sound card
>> 5. The effect is observed with both Line input drive and the UMC404HD soundcard and the internal K3S codec
>> 6. My old TS2000X does not exhibit more than 0.1dB amplitude variation with the same sound card providing audio and the same test setup
>> 7. I have verified the amplitude variations at RF with a diode detector and an oscilloscope
>> 8. The effect is clearly visible on several power meters
>> 9. This AM causes some spectral re-growth, although this is tolerable
>>
>> So given all that I am beginning to wonder if the problem is due to filter ripple in the standard K3S 2.7kHz filter? I cannot think of anything else. I was considering buying an Inrad #718 filter.
>>
>> This is very critical for EME when signals are weak at the RX side, if you have amplitude variations and you are at the threshold of detection at the receiving station this can cause decodes to fail. This is more important on 6m EME than 2m where I have more margin.
>>
>> I think that this will be quite common, has anybody else got a K3S and the equipment to check and verify my observations?
>>
>> 73
>>
>> Conrad PA5Y
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