Anan 7000DLE Mk-II PA output.

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Gary_Sitton
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Joined: Mon Mar 04, 2019 6:35 pm

Anan 7000DLE Mk-II PA output.

Postby Gary_Sitton » Sun Mar 31, 2019 8:23 pm

Hello:
I just received a new Mk-II without the internal NUC (I have my own which I use externally) and I am having a problem with the power amplifier (PA) output levels on some bands. First let me say that I'm no expert but I do know the fundamentals of RF amplifiers. With this in mind I have observed that on some bands, 17, 10 and 6 meters especially, PA drive attenuation must be significantly lowered to reach 100 watts of output into a 50 Ohm dummy load. I have been using an old Anan 100-D for years and never had a PA output issue with it or using Pure Signal (PS).
What I have found is that one may indeed compensate for the mysterious low PA output with additional drive but at the expense of increased IMD distortion. This increased distortion is probably due to driving the PA into its non-linear operating range. If it weren't for wanting to use SSB with PS rather than CW only, there would be no drive output issue. The "rub" is that you get plenty of SSB output in this over-driven PA situation but with noticeably increased IMD distortion. So, here comes PS to the rescue, but in order to have enough operational head-room to reduce the distortion, PS reduces the final pre-compensated output level to well under 100 watts.
In some sense, Apache's claim to reduce IMD levels to < -50 dB is correct but always requires using PS. This only presents a problem for any bands which may have low output requiring over-drive to reach the nominal, advertised 100 watt output. My suspicion is that these low-level bands have some sort of impedance matching issues with the output circuitry. And by the way, a set of schematics sure would help to at least confirm the possible source of this problem. I certainly hope that my 7000DLE Mk-II is not typical but that is one purpose for this post as I do not know anyone yet who owns one other than myself.
73, Gary K5AMH

P.S. No other issues yet to report and I did update to the 2.6 firmware.
73, Gary K5AMH
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w-u-2-o
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Re: Anan 7000DLE Mk-II PA output.

Postby w-u-2-o » Mon Apr 01, 2019 1:44 am

Gary_Sitton wrote:With this in mind I have observed that on some bands, 17, 10 and 6 meters especially, PA drive attenuation must be significantly lowered to reach 100 watts of output into a 50 Ohm dummy load.
This seems to be a very common observation by most people.
The "rub" is that you get plenty of SSB output in this over-driven PA situation but with noticeably increased IMD distortion. So, here comes PS to the rescue, but in order to have enough operational head-room to reduce the distortion, PS reduces the final pre-compensated output level to well under 100 watts.
That is probably not correct. If you are achieving 100W with two-tone and PureSignal active, then you are also achieving it with voice modulation. See this post: https://apache-labs.com/community/viewtopic.php?f=20&t=2862
In some sense, Apache's claim to reduce IMD levels to < -50 dB is correct but always requires using PS.
Yes, certainly. The amp's in the Apache hardware, without PureSignal, don't appear to be particularly different than any other non-linearized 12V amp. This also includes the 50V amp in the 8000. Non-linearized I only see IMD performance from the latter in the -35dBc'ish range.
My suspicion is that these low-level bands have some sort of impedance matching issues with the output circuitry.
That's very possible.
And by the way, a set of schematics sure would help to at least confirm the possible source of this problem.
Schematics are available from the factory on request.
I certainly hope that my 7000DLE Mk-II is not typical but that is one purpose for this post as I do not know anyone yet who owns one other than myself.
I'd have to say it's pretty typical.
dl4zbg
Posts: 37
Joined: Sun Apr 09, 2017 5:33 pm

Re: Anan 7000DLE Mk-II PA output.

Postby dl4zbg » Mon Apr 01, 2019 6:13 pm

Gary,

I did not expect this from the new MKII. I have been suffering from low output/ high IMD (without PS) on 10 an 17m with my 7000 DLE right from the beginning.

Good luck

Volker
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Gary_Sitton
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Re: Anan 7000DLE Mk-II PA output.

Postby Gary_Sitton » Tue Apr 02, 2019 8:05 pm

Volker:
I suspect this is just a sloppy tolerance issue with the impedance matching filter components for 17 and 10 meters. The distortion is the result of having to over-drive the PA into its non-linear region in order to increase the output. When I get a chance later, I'm going to put a scope on the output section and see where the problem lies. The issue usually is in the toroids whose ferrite characteristics or number of windings may have changed from the original design. For now I'm be happy that there seems not to be any other hardware issues. The RX is definitely much cleaner with fewer major birdies, and the TX cooling seems to be improved as well. Of course I'm comparing this all to my old Anan 100-D.
Gary
73, Gary K5AMH

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