Suggestions to improve PS operation on 7k DLE Mk2.5?

rdwing
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Suggestions to improve PS operation on 7k DLE Mk2.5?

Postby rdwing » Fri May 26, 2023 9:55 pm

I am looking for ideas or suggestions on how PureSignal performance can be improved. The factory spec for the EP4CE 7000 DLE Mk2 is -68 IMD3 on 20m @ 100w, but I have never been able to do better than maybe -50 to -55 IMD3, with either the inbuilt coupler or an external coupler.

Following are measurements on 20m, 14.1 MHz at 100w into a 50 ohm load. The radio is using the inbuilt coupler, additionally the spectrum analyzer is fed with a -55 db sampler placed between the radio and the 50 ohm load, with an additional 20dB of attenuation to ensure we are seeing the real signal and not intermodulation generated in the spectrum analyzer.

Screenshot 2023-05-26 140631.png
Inbuilt sampler 23 S-ATT
Screenshot 2023-05-26 140631.png (169.43 KiB) Viewed 4425 times

20MPSON2T.png
100w -56 sampler -20dB att -8db step att
20MPSON2T.png (11.61 KiB) Viewed 4425 times
20M100WNOPSNOISE.png
20m 100w No PS
20M100WNOPSNOISE.png (11.67 KiB) Viewed 4425 times
20M100WPSONNOISE.png
20m 100w PS ON
20M100WPSONNOISE.png (11.54 KiB) Viewed 4425 times


I was curious about the signal feeding the 100w PA, so for reference here is the output of the Orion Mk2 card with the PA disabled, both PS OFF and PS ON.

20MORIONNOPS2T.png
20m ORION ONLY PS OFF
20MORIONNOPS2T.png (12.75 KiB) Viewed 4425 times
20MORIONPSON2T.png
20m ORION ONLY PS ON
20MORIONPSON2T.png (12.46 KiB) Viewed 4425 times


Would this be a defect? What do you measure from your 7000 DLE MK2, and how can it be made better?
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w-u-2-o
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Re: Suggestions to improve PS operation on 7k DLE Mk2.5?

Postby w-u-2-o » Fri May 26, 2023 10:07 pm

IMHO the "factory spec's" are rather optimistic, to say the least.

-50dBc is typically what I see out of my modified 100D and my 8000DLE, with or without an external amplifier.

People used to be seriously into tweaking the bias of the internal amp in the 100D and 200D days, and working on reducing both internal and external crosstalk with better cabling and external couplers and switches, and some reported getting to -60dBc or thereabouts.
rdwing
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Re: Suggestions to improve PS operation on 7k DLE Mk2.5?

Postby rdwing » Fri May 26, 2023 10:25 pm

w-u-2-o wrote:IMHO the "factory spec's" are rather optimistic, to say the least.

-50dBc is typically what I see out of my modified 100D and my 8000DLE, with or without an external amplifier.

People used to be seriously into tweaking the bias of the internal amp in the 100D and 200D days, and working on reducing both internal and external crosstalk with better cabling and external couplers and switches, and some reported getting to -60dBc or thereabouts.


Thanks Scott, as always. Glad to hear the measurements are in the ballpark.

I have not been able to dredge up such information discussing those topics, but I would like to read them if you can point me in the right direction. Anyways since there is currently no functioning current sensor on the EP4CE 7000's so it would be difficult to set bias current until I get more creative, so I guess that's academic anyways.
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w-u-2-o
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Re: Suggestions to improve PS operation on 7k DLE Mk2.5?

Postby w-u-2-o » Fri May 26, 2023 11:05 pm

Gosh, that stuff from those days is unfortunately lost to the sands of time. There was much discussion on the old Yahoo Group. But when Yahoo shut the groups down there was no effective way to migrate all that, although I was able to migrate files and photos, which you can find in the forum here.

And, gosh again ;) , when folks were tweaking biases they just used an ammeter on the main power supply. First they turned the bias controls all the way down, took a baseline reading, then started increasing each bias control in turn and looking at the increase in overall current. One thing we found was that since the design is not thermally compensated the adjustment could only be an approximate one. If you tried too hard you just wound up chasing your tail. It would be the same on the 7000.
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W1AEX
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Re: Suggestions to improve PS operation on 7k DLE Mk2.5?

Postby W1AEX » Sat May 27, 2023 5:05 pm

If it helps, I have a PDF document with a suggested procedure for how to adjust the driver and PA bias that I wrote mostly so I wouldn't forget how I did it. The document explains the steps I used with my ANAN-100 back when it was new. After the adjustment it certainly was more linear when Pure Signal was not engaged but to be honest I did not notice much difference when Pure Signal was engaged.

73, Rob W1AEX

https://www.w1aex.com/archive/ANAN_Archive/ANAN_bias_adjustment_W1AEX.pdf
"One thing I am certain of is that there is too much certainty in the world."
rdwing
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Re: Suggestions to improve PS operation on 7k DLE Mk2.5?

Postby rdwing » Tue Jun 13, 2023 2:20 am

Thanks Rob, and Scott, for the info.
I measured the total draw in RX at 1.07 A, and when keyed with silence 3.4 A. I think that's pretty much in the ballpark, assuming 1A per device.

Do we know what the stock bias is meant to be on the recent 7000?
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w-u-2-o
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Re: Suggestions to improve PS operation on 7k DLE Mk2.5?

Postby w-u-2-o » Tue Jun 13, 2023 10:03 am

I don't.

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