Sampling after linear amp - worthwhile/possible?

EI2HH
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Sampling after linear amp - worthwhile/possible?

Postby EI2HH » Tue Jul 14, 2020 11:28 am

If I was to take a sample AFTER my external linear amp and run that to the sample input, would Pure Signal then be able to correct any non-linearity in the transmitter signal caused by the linear amp?

What level of signal is OK to feed in? i.e. what level level should I set my extractor to?

Thanks

A

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W1AEX
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Re: Sampling after linear amp - worthwhile/possible?

Postby W1AEX » Tue Jul 14, 2020 1:30 pm

Yes, this is the preferred way to set things up when you are using an external linear amplifier. Pure signal will then be correcting your entire transmit chain which produces the most optimal result. My RF Sampler is an Xtronic X-DC1 which attenuates the sample by -43dB and I am currently using a fixed level 10dB pad with that which results in the ANAN's auto-attenuate feature as applied by Thetis and PowerSDR mRX PS to self-adjust to around -20dB plus or minus depending on my power level which is typically between 500 watts to 1200 watts depending on the band I am on. The diagram below shows how my stuff is set up with my REV24 200D. I have also used a fixed level 20dB pad and that works fine as well.

73, Rob W1AEX

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EI2HH
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Re: Sampling after linear amp - worthwhile/possible?

Postby EI2HH » Tue Jul 14, 2020 3:28 pm

Thanks for the useful reply Rob. How does one tell the Annan 7000 to listen to the 'bypass' input? Mine has a bnc marked bypass, no loopthrough connector which I think the older boards had.

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Re: Sampling after linear amp - worthwhile/possible?

Postby W1AEX » Tue Jul 14, 2020 4:21 pm

In Thetis or PowerSDR mRX PS, look at the Ant/Filters tab in the menu settings and on the right side you will see a checkbox for the "BYPASS on TX" setting. That will direct the ANAN to listen on that port while transmitting.

73, Rob W1AEX
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EI2HH
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Re: Sampling after linear amp - worthwhile/possible?

Postby EI2HH » Wed Jul 15, 2020 10:54 am

Great! Thanks for the info.

EI2HH
EI2HH
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Re: Sampling after linear amp - worthwhile/possible?

Postby EI2HH » Wed Jul 15, 2020 11:48 am

Final question (can't promise...) how do I know if the Bypass input is getting an acceptable signal level?

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Re: Sampling after linear amp - worthwhile/possible?

Postby w-u-2-o » Wed Jul 15, 2020 1:31 pm

Read all of the sticky/tacked posts in this very PureSignal sub-forum, especially the "External feedback power level" topic, where you will find your answer.

73,

Scott

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