Pure Signal and a Trapezoid pattern

Bill in Georgia
Posts: 51
Joined: Sun Apr 09, 2017 8:03 pm

Pure Signal and a Trapezoid pattern

Postby Bill in Georgia » Thu Aug 03, 2017 5:22 pm

Running a 200D with a conventional wiring hook up for PS ... Can I tap the lines to pick up X & Y to feed a scope for the trap pattern, without messing up PS??

Bill ... kc4pe
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w-u-2-o
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Re: Pure Signal and a Trapezoid pattern

Postby w-u-2-o » Fri Aug 04, 2017 12:42 am

Bill,

It's not crystal clear from your post what your "conventional wiring hook up" is. Are you running an external amplifier with an external coupler? Or just barefoot with the internal coupler?

73,

Scott
AB2EZ
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Location: Princeton, NJ

Re: Pure Signal and a Trapezoid pattern

Postby AB2EZ » Fri Aug 04, 2017 1:10 am

As a separate issue...

If you want to display a traditional AM or DSB trapezoid pattern... RF output v. audio Input... you will need to take into account the relatively large delay (latency) between the applied audio input and the modulated RF output.

Stu
Bill in Georgia
Posts: 51
Joined: Sun Apr 09, 2017 8:03 pm

Re: Pure Signal and a Trapezoid pattern

Postby Bill in Georgia » Fri Aug 04, 2017 2:30 pm

Thanks, Yes am running an amplifier so using the recommended setup, coupler, etc.
The reason I ask, I have always tuned the amplifier via the trapezoid pattern. But pulled the scope when I set up Pure Signal..
Thanks,
-Bill
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w-u-2-o
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Re: Pure Signal and a Trapezoid pattern

Postby w-u-2-o » Fri Aug 04, 2017 3:14 pm

Hi Bill,

Obviously it is no problem to tap off of the audio. And you can purchase a power divider (e.g. from Mini-circuits, like this one) to properly split the coupler output. However, I think Stu nailed it when he noted that this will not work because of the inherent latency between the audio and the RF, which will be somewhere between 30 and 100mS, depending on your specific buffer and filter settings in PowerSDR.

If you are running AM, there is another way to accomplish this, though, and that is to use a detector to obtain demodulated audio from the radio output (input side of the amplifier). While I wouldn't recommend using a CleanRF brand sampler for anything, they do make a detector that can be used for this approach.

However, all that said, if you are running PureSignal you don't really need to go to all the trouble. You can use the built-in PureSignal AmpView display to see exactly what your entire RF path is doing, linearity-wise. If you are pushing things too hard, the AmpView display will show you that immediately, as you will clearly see the gain curve flatten out towards the top. Just turn it down a bit, because PureSignal will fight you tooth and nail to make it linear, and the more you compress the external amp the harder PureSignal fights.

73!

Scott
Bill in Georgia
Posts: 51
Joined: Sun Apr 09, 2017 8:03 pm

Re: Pure Signal and a Trapezoid pattern

Postby Bill in Georgia » Sat Aug 05, 2017 3:16 pm

Again Thanks Guys!!

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