SAM MODE "ANOMALY"

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Paul
Posts: 343
Joined: Fri Feb 17, 2017 9:52 am
Location: SW UK

SAM MODE "ANOMALY"

Postby Paul » Fri Nov 02, 2018 8:26 am

Using an RSP2 and SDRuno, I have long been puzzled by anomalies with the operation of the SAM mode with SSB transmissions.
No matter what how I "tweak" the PLL T.C. and/or Filter Bandwidth in the associated Settings panel, corruption of the received signal persists.
However, experimenting (as usual), I have found a suitable transmission to experiment with and the result is as follows:
Tuned frequency 5505 KHZ (Shannon Volmet) that is typiclly corrupt for me using SAM mode.
However, tuning to 5504.6 KHZ produced a perfectly clear signal, but which "drifted" back and forward over several HZ.
This effect has recurred for me sporadically in all versions of uno from 1.2 to the current 1.23 that I am currently using.
It works just fine for AM/DSB transmissions.
Is there an obvious explanation for this that as a newbie that is quite obvious to the knowledgeable?

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DanubeBCL
Posts: 203
Joined: Sat Jul 02, 2016 12:39 pm

Re: SAM MODE "ANOMALY"

Postby DanubeBCL » Fri Nov 02, 2018 11:36 am

Shannon Volmet uses USB. This mode has no carrier which Sync AM could lock to. When you use SAM for SSB transmissions the detector will lock to any strong peak in the modulation spectrum close to the nominal frequency at random. This results in an unstable audio pitch.
SAM is meant for AM transmissions which have a carrier.
73s, Heinrich

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Paul
Posts: 343
Joined: Fri Feb 17, 2017 9:52 am
Location: SW UK

Re: SAM MODE "ANOMALY"

Postby Paul » Sat Nov 03, 2018 7:09 am

Thanks very much Heinrich.
My ignorance is obvious, but I'm learning thanks to folks like you (I never knew that SSB transmissions had no carrier frequency).
Now, of course it makes perfect sense to me :oops:

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g1hbe
Posts: 475
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: SAM MODE "ANOMALY"

Postby g1hbe » Sat Nov 03, 2018 8:36 am

Hi Paul :-)

It would help if we called SSB by its proper name - Single Sideband Suppressed Carrier. Then everyone would instantly know what was going on. Modes USB and LSB are the ones to use, keep SAM for AM.

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Andy

Paul
Posts: 343
Joined: Fri Feb 17, 2017 9:52 am
Location: SW UK

Re: SAM MODE "ANOMALY"

Postby Paul » Sat Nov 03, 2018 10:35 pm

Thanks yet again Andy (now I don't feel quite so daft!).
Because it worked with DSB (which is really AM?) I had assumed that it would work the same for ssb - especially since it often did, although, of course, the manual is quite speific.

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