ORION MK2 IMD3/5

dj1yr
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ORION MK2 IMD3/5

Postby dj1yr » Mon Mar 08, 2021 4:36 pm

Hello,

I have checked the IMD3 on two of my Orion MK2 boards, what i saw does not look good
On the search for the cause I landed at the pre amp, at the "primary winding" the IMD3 is ok (DAC out), see picture 1, on the secondary side of T2 is suddenly IMD3 present, see picture 2.
T2 also has 10db level drop in that case.
If I compare the schematic with the data sheet of ADT2-1, T2 and T9 are inserted the wrong way around, as I understand it, the point on the ADT at PIN1 and PIN1+3 are primary, but on the board directed towards MMIC.

Can someone maybe do the measurements on his Orion MK2?

My measurement setup was, Orion MK2 TX -> dummy load, spectrum analyzer RF IN + 30db ATT with 1:1 measurement tip (500Mhz Agilent).

Pictures are labeled 1-3, where picture 1 DAC out - input T2, picture 2 - out T2-input MMIC, picture 3 -output T9

i have removed all component values so far, hope that is ok.

Datasheet ADT2-1T https://www.minicircuits.com/pdfs/ADT2-1T.pdf

73´René
Attachments
IMD Orion MK2.pdf
IMD3 with Orion MK2 PA
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pre_schema.jpg
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1.jpg
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3.jpg
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Board MK2.jpg
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Last edited by dj1yr on Mon Mar 08, 2021 7:20 pm, edited 4 times in total.
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KA5KKT
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Re: ORION MK2 IMD3/5

Postby KA5KKT » Mon Mar 08, 2021 6:02 pm

...way out of my league, but I compliment your good documentation!
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Re: ORION MK2 IMD3/5

Postby Joe-W4WT » Mon Mar 08, 2021 7:44 pm

Hi Rene,

I took a look at the schematics for the 8000 and the 200D as I've had both of them along with the 7000 DLE MKII and have schematics for all. I see the same transformer and pinout shown on the 8000 but the 200D used a different transformer for this same functional circuit. The 8000 shows the same transformer and pinout as the 7000 DLE MKII which, as you mention, appears to be backwards in both cases. In the 8000 they don't use the center tap so it probably doesn't matter if it is backwards but the 7000 does, according to the schematic, so it is important it be installed correctly, I would think.

The 200D uses a TC4-1T rather than the ADT2-1-T+ and it IS used with the center tap. It also is interesting that the pinouts for the TC4-1T are not the same as the ADT2-1-T+ but they match perfectly the pinouts on the schematic of the 7000 DLE MKII. It's primary pins are 6 & 4 and 1,2,& 3 are the secondary with 2 being the secondary CT.

It almost make one think they simply inserted the ADT2-1-T+ in the board just like they did the 8000. Of course, I assume the schematic to be correct. It may not be. If they really use the CT and it is physically inserted as your picture shows then it is indeed backwards. A quick ohm meter test to see where pin 1 of the ADT2 actually goes should confirm if the schematic is correct and the device is in backwards or not. You may have done this already but I didn't see it in your post.

73,

Joe W4WT
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w-u-2-o
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Re: ORION MK2 IMD3/5

Postby w-u-2-o » Mon Mar 08, 2021 8:26 pm

Rene,

Are they really "backwards" from a functional standpoint? Looking at T2, the PCB layout you pictured implies Pin 1 going to C27 and Pin 3 going to C33, reversed from the schematic. However, if Pin 4 is ground, then it really doesn't matter. Is Pin 4 ground? And is Pin 2 also ground?

In other words, it could just be a schematic error. Maybe you could confirm that is the case?

BREAK

Joe,

The 7000 and 8000 both use the same Orion MKII board, or at least that's what I've been told. I have an Orion MKII board in my 8000.
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Re: ORION MK2 IMD3/5

Postby K1LSB » Mon Mar 08, 2021 9:11 pm

If the transformers are in fact mounted backwards then the secondary CT in each case wouldn't be grounded despite the schematic showing the CT to be grounded, since the ADT2-1T pdf says pin #2 isn't used. If that's the case then the circuit would not work as designed (I'm not sure how it would work, but degraded IMD may be one of the consequences of that situation).

It would be great if Doug W5WC was in a position to comment here.
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Re: ORION MK2 IMD3/5

Postby Joe-W4WT » Mon Mar 08, 2021 10:42 pm

Hi Scott,

My 8000 board is an early one (they had 3 or 4 different boards) and is different in several areas, including this one, than 7000 DLE MKII. My board, for instance, does not use PGA103+ amps; instead it uses the GALI-51+ in this circuit. I just exposed the board and checked and found that pin1 indeed does go to either C33 or C27. Hard to tell with the low resistance of the transformer secondary. Regardless, this means the transformer for my 8000 board is indeed "backwards" which is what my 8000 schematic shows as well as the 7000 DLE MKII schematic. But, since my board doesn't use the center tap, it doesn't really matter. My board also doesn't have T9. The circuitry is quite different than the 7000.

I suspect the later 8000's probably do use the same board as the 7000's but the earlier ones don't. Doug helped me determine my board was version 3.2 back in 2017.

73,

Joe

Update: I hit enter a little early here :-) I went back and decided to confirm the CT was not grounded but in fact it is! The transformer is indeed in backwards and the CT is grounded with pin 4 going to FL1. I confirmed that with the meter and visually seeing the trace. I also was able to visually see that pin 3 does go to C27 and pin 1 goes to C33. Thus, we have what is listed by mini-circuits as the secondary actually hooked up as the primary with the CT grounded and the primary hooked up to the secondary of the circuit. I think somebody goofed here.

Joe
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Re: ORION MK2 IMD3/5

Postby Joe-W4WT » Mon Mar 08, 2021 11:07 pm

It would be interesting to know if pin 2 on the transformer in the 7000 MKII board is grounded. It is not on my 8000. If it is, then a quick bit of hot air work and flip this thing around 180 degrees should solve the problem. Obviously T9 would need the same done to it assuming it ohms out correctly too. The area is fairly clear on my board and would an easy change.

Joe W4WT
dj1yr
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Re: ORION MK2 IMD3/5

Postby dj1yr » Tue Mar 09, 2021 4:38 am

Hello,

on my MK2 board pin 2 are grounded, at least according to the multimeter.

I checked the inductance, PIN1+3 = 34µH (1+2 II 2+3 ==n.c.), 4+5 II 5+6 ==17,4µH.

I wonder what happens when they are "correctly" installed, can it be that the gain increases sharply, which leads to overdriving the step ATT (max. 16dbm/1db point on KW).

Maybe one of the developers comments on the subject, in any case what is wrong with my two boards, there was also someone else who noticed the "quality" of the TX signal -> viewtopic.php?f=17&t=3542&p=12080#p12079

T2 would have to convert the 50Ohms into 2x 50Ohms for the MMIC, I think I this wiring they are used as a 1:1 transformer, which brings a small mismatch, but should be acceptable.

73´René
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Re: ORION MK2 IMD3/5

Postby K1LSB » Tue Mar 09, 2021 10:24 am

My point was that if the transformers are mounted backwards it doesn't matter whether pin 2 is grounded or not because the ADT2-1T pdf says pin #2 isn't used, so the secondary winding can't possibly be functioning as the schematic depicts.
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Re: ORION MK2 IMD3/5

Postby dj1yr » Tue Mar 09, 2021 4:44 pm

therefore I suspect a 1:1 configuration, because pin 5 is not grounded (ADT wiring not schematic of Apache)
Therefore I can also measure half inductance between 4-5 and 5-6.

I have designed test boards which are being manufactured to find the fault, I don't want to test on the Orion board, they are too valuable for that.

But no matter what configuration would be correct, that does not explain the IMD increase, the transformer is specified for this range, overload will not be it.


73´René
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Re: ORION MK2 IMD3/5

Postby Joe-W4WT » Tue Mar 09, 2021 5:38 pm

My point on checking pin 2 to see if it was grounded was simply to see IF the package was rotated 180 degrees, would the CT then be grounded like the schematic shows. I knew pin 2 wasn't used on the transformer itself.

I will be removing and reinstalling the transformer in it's correct orientation on my 8000 board later today. I'll report back as to what I see afterwards.

Joe W4WT
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Re: ORION MK2 IMD3/5

Postby K1LSB » Tue Mar 09, 2021 6:10 pm

René,

Whether the configuration is 1:1 or 2:1 is irrelevant. The crux of the problem with the circuit is that there is no center tap on the secondary winding, so effectively there is no completed circuit on that side: the secondary simply feeds into capacitors at each end of the winding with no path to ground (i.e., no completed circuit) anywhere in the circuit. The secondary circuit can't possibly be behaving per design because a critical piece of the circuit (a path to ground) is missing!

Mark

EDIT: The more I ponder that condition, the more I tend to suspect that right there is the source of your IMD trouble. RF energy injected between 2 capacitors with no damping (or grounding) between them is an open invitation to oscillations and is almost certainly contributing to elevated IMD levels (which is really nothing more than poorly damped harmonics).
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Re: ORION MK2 IMD3/5

Postby w-u-2-o » Tue Mar 09, 2021 8:22 pm

Joe-W4WT wrote:My point on checking pin 2 to see if it was grounded was simply to see IF the package was rotated 180 degrees, would the CT then be grounded like the schematic shows. I knew pin 2 wasn't used on the transformer itself.

I will be removing and reinstalling the transformer in it's correct orientation on my 8000 board later today. I'll report back as to what I see afterwards.

Joe W4WT

This is going to be very interesting!

Is T9 also backwards?
dj1yr
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Re: ORION MK2 IMD3/5

Postby dj1yr » Wed Mar 10, 2021 1:28 am

w-u-2-o wrote:
Is T9 also backwards?


I would think so, yes


@Mark
this will be the explanation for the behavior, I will try to reproduce it on the test board, the material is ordered
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Re: ORION MK2 IMD3/5

Postby LA2NI » Wed Mar 10, 2021 3:47 pm

Hi Scott.
Thanks for showing me this. As I am not following this forum I have not been aware of the wrongly installed transformers. I took a look at my version of the Orion MK2 board and it has T2 installed the wrong way around with the 50 Ohm side to the Gali-6+ amplifiers. And the center point (pin2) is not grounded at that side but it is grounded at the input side.
The output transformer T9 is not installed on my board as it is an early board without the new attenuator installed.
By using the transformer the wrong way around, the inpedance matching of the amplifier is wrong, both on the input side were it is transformed from 50 Ohm to 25 Ohm and on the output side were the load is not 100 Ohm but 25 Ohm due to the 50 Ohm load presented by the attenuator. So this might be the reason for the bad IMD in the amplifier. When using Pure Signal this is totally masked by the process!
I am going to turn T2 180 deg. I might get a bit more gain than before but I do not think my version of the board is influenced so much.
73, Kjell
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w-u-2-o
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Re: ORION MK2 IMD3/5

Postby w-u-2-o » Wed Mar 10, 2021 3:57 pm

Hi Kjell,

Thanks for weighing in on this.

Wow, this is bad! :o

I'm going to wait for Joe's results but, damn, I'm going to be highly motivated to take apart my 8000 and possible turn things around, also if his results are good.

73,

Scott
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Re: ORION MK2 IMD3/5

Postby K1LSB » Wed Mar 10, 2021 6:09 pm

For my own part, I'm not nearly as concerned about this as some others here, if only for the simple reason that (as Kjell has already noted) PureSignal very effectively and completely masks any IMD problem, and I always operate with PS enabled.

Truth be told, I've been aware of the poor IMD problem with this radio from very early on -- the problem is very obvious to anyone who is watching the panascope while transmitting with PS disabled (the displayed signal is very dirty). However, as soon as PS is engaged the signal immediately cleans up to show an IMD of -60dB or better, which is far cleaner than any other amateur radio in existence. So I decided to simply not worry about it (and that's really saying a lot, because I have a truly horrible case of OCD, which is the main reason why I sprung for this radio in the first place -- the very sight of splatter on a waterfall makes my OCD flare up big-time).
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Re: ORION MK2 IMD3/5

Postby w-u-2-o » Wed Mar 10, 2021 6:30 pm

I made the following drawing to assist in understanding this problem. If someone could check to see if I've got all the numbers correct, and if all the pads that are supposed to be ground really are ground, that would be great.

Thanks,

Scott

Orion MKII Transformer Problem.jpg
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DL1KD
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Re: ORION MK2 IMD3/5

Postby DL1KD » Wed Mar 10, 2021 8:20 pm

Hi René, thanks again for your effort.
Scott, thanks for the summary.

Back when the Angelia and Orion boards could be bought separately to use in homebrew projects, it has already been noticed in 2018 that the Orion MK2 has a realy bad IMD3. René has already made measurements at that time.
But of us self-builders we have that then no longer pursued. We then stayed with Hermes / Angelia.
2 weeks ago René and I got in touch, because I wanted to buy an Orion MK2 board to be able to use diversity and exchange it for my Hermes board.
Here I have the claim to have an IMD3 without predistortion better than >50dBc to drive a super linear 5W PA. (Driver vor LDMOS)
Just, state of the art.

I am very curious about the results, as well as a statement from Apachelabs.

Thanks to all
73 Alex DL1KD
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Re: ORION MK2 IMD3/5

Postby KX4M » Wed Mar 10, 2021 8:21 pm

Is this separate from the inductor issue that QST found in their March 2021 ANAN-7000DLE MKII review, that Apache resolved for them?
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Re: ORION MK2 IMD3/5

Postby administrator » Wed Mar 10, 2021 8:49 pm

Please do not reverse T2 or T9, these transformers are reversed on purpose to introduce a slight mismatch and reduce gain of the stage, with these reversed you risk exceeding the maximum input for the step attenuator and damaging.

The Orion MKII has been designed keeping in mind:

1. PureSignal
2. Eliminate the RD15 drivers for the 7000DLE since adding the RD15 drivers in the mix results in worse IMD even with PureSignal enabled due to larger memory effects in this stage, the Hermes/Orion?Angelia Driver has better IMD without Puresignal, however, when looking at the IMD levels at 100W they are worse that the 7000DLE MKII due to larger memory effects of the entire Tx chain.
3. Orion MKII is a part of the overall transmit chain, adding an LDMOS amplifier (for experimenters) will result in -60dB IMD3 easily with PureSignal ON and that is the design goal.

The Tx chain on the Orion MKII is stable and with excellent Tx phase noise, the additional IMD introduced due to the mismatch introduced to control gain is completely corrected by PureSignal.

Hope this helps,

Abhi
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Re: ORION MK2 IMD3/5

Postby w-u-2-o » Wed Mar 10, 2021 10:28 pm

Abhi,

What if we reversed them, then cut in a pad (attenuator) on the trace at the output of T9? How much does it need to come down?

Thanks,

Scott
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Re: ORION MK2 IMD3/5

Postby K1LSB » Thu Mar 11, 2021 1:38 am

Abhi,

Thank you very much for that post, sir, it is exactly the clarification this thread needed.

Mark
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Re: ORION MK2 IMD3/5

Postby dj1yr » Thu Mar 11, 2021 3:09 am

Thank you very much for all the replies.

the attenuator must be about 5-6db

As long as PD is not in the HW, the goal for me is to have a clean RF chain, intentionally "mismatching" a stage is a very poor solution and has the charm of tinkering, the clean solution would be a fixed ATT at the input and/or output.

I will make test setups and experiment, it will probably end up a mounted circuit board with proper transformer/splitter/combiner + ATT

I hope this HW bug will be fixed in the upcoming revisions, it increases the cost by 3 SMD resistors.

it should also be the goal of the developer to keep the basic system clean, PD is just an addition


73´René

edit:
I quickly made two boards, which are mounted vertically on the original tr2/tr9 pin's, once with mini circuits splitter/combiner ADP-2-1 or JPS and once for the ADT-2-1 transformer, both with the possibility to mount an ATT.
Attachments
preamp_Board.jpg
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tr_board.jpg
tr_board.jpg (109.06 KiB) Viewed 1122 times
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Re: ORION MK2 IMD3/5

Postby administrator » Thu Mar 11, 2021 8:57 am

w-u-2-o wrote:Abhi,

What if we reversed them, then cut in a pad (attenuator) on the trace at the output of T9? How much does it need to come down?

Thanks,

Scott


Hi Scott,

Restoring full gain to the MMIC amplifier creates two problems:

1. The MMIC amp at full gain behaves like a comb generator on HF, although these devices are specified to operate from DC through to several Gigahertz they have excessive gain on HF.
2. Puresignal does not like the AMP at full gain and the correction factor goes down considerably for the entire Tx chain.

None of the above can be corrected by putting an attenuator before or after this stage.

Abhi
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Re: ORION MK2 IMD3/5

Postby dj1yr » Thu Mar 11, 2021 10:55 am

the GALI51+ have 18-20db gain in the HF range, so the signal must be at most -10dbm to reach the 1db compression point.

Assuming that the DAC brings 0-3dbm level, you need round a 10db ATT PAD between DAC and MMIC amplifier if you don't want to push the Step ATT to the limit.

So you have about +8dbm on the Step ATT.

I think the comp generator effect shows an absolutely overdriven MMIC.

https://www.minicircuits.com/pages/s-pa ... GRAPHS.pdf
Last edited by dj1yr on Thu Mar 11, 2021 1:52 pm, edited 3 times in total.
dl4zbg
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Re: ORION MK2 IMD3/5

Postby dl4zbg » Thu Mar 11, 2021 11:31 am

GALI?

in my schematics Version 5.2 I find the PGA-103+ MMIC.

When I checked the quality of the transverter output at 10dBm or higher I measured abt -25dBc, at 0dBm it was about -45dBc. I expected better values. Not I know why. :shock:

Pure signal can hardly be used with transverters.

TNX

Volker DL4ZBG
dj1yr
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Re: ORION MK2 IMD3/5

Postby dj1yr » Thu Mar 11, 2021 1:08 pm

in my wiring diagram Gali 51+ are installed
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Re: ORION MK2 IMD3/5

Postby LA2NI » Thu Mar 11, 2021 2:01 pm

First one comment to DJ1YR: The GALI51+ does not have 38-40 dB gain but only around 18 dB on HF. When 2 of them are in Push Pull the gain is 3 dB higher.
Today I found the prototype I made for the new 5W PA using AFT05MS003NT1 in Push Pull and did some measurements on it using a Hermes with excellent IMD as a driver.
At 14,2 MHz, 5W PEP the IM3 is at -38 dBc (ref.PEP) and IM5 at 43 dBc. At the same frequency and 3W PEP, the IM3 is at -43 dBc and IM5 is more than 65 dBc (not visible in the noise).
The IMD is a bit lower at 50MHz but still IM3 at -32 dBc at 5W PEP.
As I do not have an Orion MK2 board with this PA, I can not confirm that the IMD is kept in the production but It would be very interesting if someone with this board can measure it. I believe that if it is used together with a transverter, the power used would be much less. If I measure at 1W PEP, the IM3 is at -53 dBc so this should be good enough for use with transverters.
73, Kjell
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Re: ORION MK2 IMD3/5

Postby LA2NI » Thu Mar 11, 2021 3:35 pm

I forgot to mention that it is possible to use Pure Signal locally if the feedback can not be taken from the transverter PA. Just use a splitter and attenuator from the output of Orion MK2 board and back to the PS input.
73, Kjell
Last edited by LA2NI on Thu Mar 11, 2021 7:17 pm, edited 1 time in total.

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