I have seen a good bit of this sort of thing .. having a noise blanker on will
cause this as well as a lot of DSP as I have observed on my FT1000mp also you
can have mixing within a soundcard cause this I believe where you have two
strong signals as well as the 60hz problems.just my thoughts 73 Morris wa4mit
On Monday, December 11, 2017, 8:43:22 AM CST, David Tiller
<dtil...@captechconsulting.com> wrote:
#yiv2463065764 #yiv2463065764 -- P
{margin-top:0;margin-bottom:0;}#yiv2463065764
I was going to say the same thing that Bill S. said, however I noticed that the
difference frequency was more like 80 Hz than a multiple of 50 or 60. That's a
little odd. Hopefully the station has all fancy soundcard-based audio
processing turned off.
Did you notice harmonics on the waterfall display at the same time? I see (and
can generally hear) lots of stations apparently overdriving the heck out of
their rigs. I've seen 1 station transmitting 1st thru 7th harmonics! (Yes, I
made sure I turned off preamps, reduced RF gain, etc to try and make sure it
wasn't on my end).
--
| David Tiller | Senior Manager |
| dtil...@captechconsulting.com |
| c 804.304.0638 / o 804.355.0511 |
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From: Bill Somerville <g4...@classdesign.com>
Sent: Monday, December 11, 2017 8:44 AM
To: wsjt-devel@lists.sourceforge.net
Subject: Re: [wsjt-devel] dual transmit On 11/12/2017 13:21, Jerry S wrote:
> Is it possible to transmit on two frequencies at the same time with
> wsjt-x FT8.
> Below are screen prints receiving K4UX sending on two frequencies
> yesterday on 30m.
> Jerry W8DLD
Hi Jerry,
the things to note here are that the messages are the same, the SNR
numbers are very different, and the frequency separation is a multiple
of 60 Hz (particularly a multiple of 120 Hz).
This all adds up to his signal being modulated by line hum in the audio
domain, from a full-wave rectified, but not fully smoothed, PSU. I would
guess the source of the noise is at the transmitting end but that is not
conclusive as he is the strongest signal. W7OM and KE4FW are only a
little weaker and have no images to I would say with a high probability
that the problem is at K4UX's end. Noise mixing producing unwanted
images only 24 dB down from the fundamental are not desirable although,
by far, not the worst see on the bands.
73
Bill
G4WJS.
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