[Elecraft] Signal analysis with the P3

[Joe Subich, W4TV]

A "spike" on the left of a USB signal is normally an indication of
insufficient carrier suppression (carrier leakage).  Signal to the
left of that is generally insufficient opposite sideband suppression
(sideband leakage) or regenerated sideband due to excess IMD in the
transmitter.

However, if the other station is using ESSB with excess low frequency
content below 150 - 200 Hz, the spike can be a "false carrier" due to
ringing in the modulator when it is over driven by the excess low
frequency content.  "False carrier" or modulator ringing is almost
always accompanied by IMD and regenerated opposite sideband.

Most SSB users will tend to zero beat the false carrier.  That will
cause a "robotic" or "hollow" sound because excess low frequency
content, the signal is actually tuned slightly off frequency, and
the normal/regenerated sidebands are not producing the same/in phase
audio.

73,

    ... Joe, W4TV


On 4/29/2014 9:31 AM, Slava Baytalskiy wrote:
> Hello everybody!
> Ever since i got my new P3 - i've been looking at people's signals (naturally).
> And i've noticed the following:
> When using USB on 10 meters, talking locally, there are a couple of folks that use ICOM radios and i can see these spikes on the left of the carrier.
> Normally, in USB, all the signal shows up on the right, correct?
> But with these guys there's a lot of signal on the left as well.
> And they sound a bit robotic, as if they were off frequency a bit. But they aren't.
> When they switch to, say, Yaesu or a Kenwood i don't see that same graph.
> But on the ICOM its very pronounced (except the older ones like 756 Pro III).
> Saw it last night with an ICOM IC-7000.
>
> Is this normal? Has anyone else noticed this?
> This P3 is certainly giving me a lot of insight i didn't have before...
>
> Thanks in advance!
>
> Slava B
> W2RMS
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to lists at subich.com
>