-74dB IMD on RF1 output with Puresignal

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KG4ODA

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Jul 12, 2021, 2:34:37 PM7/12/21
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I am working on making duplex VHF transverter to enable use of Puresignal on VHF. Tried testing IMD of low power output. Got -63 dBt IM3 and with Puresignal it gets down to -74 dB into adjacent 3 kHz channel. I am surprised that Puresignal makes a difference at such low IMD level. Internal PA was disabled. 

KG4ODA

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Jul 12, 2021, 3:35:00 PM7/12/21
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some more scans:
hl2-28mhz-ps.png
RF1 out, 100% drive, no PS.

hl2-no-ps.png
No PS, noise output, 20dB compressor in PowerSDR, 100% drive.

hl2-ps_2.png
Puresignal ON, 100% drive. Reaching IMD limit of Anritsu MS2721b analyzer.

KG4ODA

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Jul 12, 2021, 3:48:07 PM7/12/21
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Ampview window. If only my 800W LDMOS amp looked this good.
ampview.png

Duncan Clark

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Jul 12, 2021, 4:04:34 PM7/12/21
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In message <dc26fe6a-c924-4261...@googlegroups.com>,
KG4ODA writes
>I am working on making duplex VHF transverter to enable use of
>Puresignal on VHF.

Snap.

I have built OH2GAQ duplex transverters for 6m, 4m and 2m.

>Tried testing IMD of low power output. Got -63 dBt IM3

I get around that on 6m and 4m out. Not checked 2m yet.

>and with Puresignal it gets down to -74 dB into adjacent 3 kHz channel.

I haven't yet run them as a true duplex feeding back to the HL2.
Concentrating on getting tghe power up and boxing things up (which I
find is the hardest bit).

I tried on 28Mhz but as I was running through my HF -50dB coupler I
simply had too little feedback with the low level output. I am also at
the limit of my measurement.

Normally on HF at 400W out I see a 20dB improvement on IMD when running
PureSignal, down to around -50 IM3

Duncan

--
Duncan Clark
G4ELJ

KG4ODA

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Jul 12, 2021, 4:26:00 PM7/12/21
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Thanks Duncan.
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