Re: [wsjt-devel] Does the FT8 signal spike at the beginning of each transmission?

[Bramax <mic...@tw...>]

Hi,
I haven't any RFI issue but I noted the spike at the beginning of any 
trasmission.
I use an Icom 7610 and on the waterfall I clearly see a kind of spike 
that occupies the complete bandwith of audio channel. In my case 
100-2800 Hz.
I can see it at any TX start.
I use the USB audio connection between my rig and the PC.

73s,

Maurizio I2NOY

Il 12/04/2019 08:52, Paul Randall ha scritto:
> Ed
> 
> I can reproduce this on my setup where my antenna is not good for 160m - 
> causing bad RFI which crashes the USB audio link to the PC. If I start 
> transmission on 160m with very low power and ease it up I get almost to 
> full power before the link fails.
> 
> I’ve seen no evidence of a spike, actually my observation suggests the 
> commencement of audio seems to be shaped to avoid one.
> 
> My guess is that you have RF feedback problems.
> 
> Kind regards
> 
> Paul G3NJV
> 
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for 
> Windows 10
> 
> ------------------------------------------------------------------------
> *From:* Ed Stokes <w1...@co...>
> *Sent:* Friday, April 12, 2019 7:05:54 AM
> *To:* WSJT software development
> *Subject:* [wsjt-devel] Does the FT8 signal spike at the beginning of 
> each transmission?
> I’m curious about something I observe about the FT8 signal modulation.
> 
> It appears to produce a pronounced spike in the audio at the beginning 
> of each 15 second transmission.
> 
> When I operate on 160, 80 and 40 meters especially this spike will cause 
> the program to stop producing audio.  My computer, a mac mini, is 
> relatively close to the 160m dipole being used on these bands, about 50 
> feet.
> 
> If I throttle back to -41 dB or so I can make the transmission begin 
> without stopping the audio, although the spike is still evident.
> 
> If I then gradually increase the “Pwr” slider I can increase the power 
> without causing the audio to crash.
> 
> If I leave the power increased the audio will crash immediately after 
> the next transmission period begins.
> 
> Is this a known problem?
> 
> 73, Ed
> W1KOK
> 
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