(tr)uSDX power, efficiency and filter optimisation

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hb9hem
 

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(tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

Hi all,

does anyone have a positive result with the *Rxxxx* kit?

I just built it, and it does work, but the efficiency is only 60-75% and the output power is only 2.5-4W @ 12V VCC.
I've been playing around with squeezing and stretching the windings on the coils, and I rewound some, but there's no significant impact. It all looks nice and tidy under the microscope, no cold solder joints, no shorts, everything triple checked. The scope shows a nice sine-wave, Vpp is reasonable, SWR measurements are correct, power and efficiency are correct. Fiddling with PA Bias max (menu 8.2) yields barely any improvement. If it wasn't for the low efficiency and power it'd be absolutely brilliant. Even as it is I'm quite fond of this little thing. But I want that >80% efficiency...
The heat camera tells me that some coils get warm, but not all. What makes me very suspicious is that some capacitors get warm (just some, not all). Maybe some components of the kit are not to spec? This would be very difficult to debug.

By the way, the *Rxxxx* kit is not approved by DL2MAN (yet?). Are there issues with this kit?

Cheers,
Mark HB9HEM
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Re: Good results with *Rxxxx* kit?

Post by DL2MAN »

Hello Mark,

first of All: The Reason, *Rxxxx* is not approved yet, is simply due to my time constraints. They have sent a kit, I´ve built half way, but I don´t find the time to finish it and document along with it. I couldn´t see any problem yet.... They most likely will get approval.

As Faraaz said:
Class E is critical, and component tolerances alone can kick a Filter out of Specs. You need to compesate for those tolerances by messing with the coils:

STEP1:
Start with LX2 (X Stands for Band-Slot, eG 1 for 20m) ->
While (tr)uSDX is on, select the Band you want to mess with. Then switch it off (disconnect it from Power, and unmount the RF Board) Connect a NanoVNA to it like so:
S11 Port of NanoVNA to RF and GND Pins (RF is INNER SMA Connector, GND is OUTER)
S21 Port to SMA Connector of RF Board.
20220315_124942_resized.jpg
20220315_124942_resized.jpg (215.32 KiB) Viewed 20827 times
Use a self made Adapter like this one (from Pin Header and SMA Socket):
adapter.JPG
adapter.JPG (55.88 KiB) Viewed 20827 times
Use S21 Function "LogMag" and cover Frequency of Fundamental + at least double frequency and above.
Then use your markers to mark your second targeted 2nd harmonic. In case of 40m Band: Desired Frequency abt 7,1MHz, so Second Harmonic Notch should be at 14.2MHz.
IGNORE THE FUNDAMENTAL Frequency at this time !!! YOu cannot tweak that with NanoVNA, as it is a 50 Ohm System, while LX1 is more in the 10 Ohm Ragne. Once again: IGNORE THE FUNDAMENTAL Frequency /LX1 on your NanoVNA !!!
Then tune your Coil LX2 to be spot on that (2nd harmonic Notch) Frequency. Squeeze Windings, Seperate them. In worst case, if you don´t get there: Add or remove windings. If compressing turns get you closer to target, but not spot on, then add a turn.
If seperating turns get you closer but not spot on remove 1 turn.
When you achieved the second harmonic Notch being on Frequency leave it and: Never touch it again !!!!

STEP 2:
Then remove NanoVNA and connect the PCB to Mainboard again. Switch it on.
Set SWR Meter to PWR and Efficiency
TX in CW with Straight Key into Dummy Load at your target frequency.
Then go lower in frequency and higher in freqency and compare.
If power and efficiency increase (get higher) at lower frequencies, LX1 must be lowered in inductance.

Vice Versa goes for: if your power and efficiency increases (gets higher) at higher frequencies, LX1 must be increased in inductance.

Increasing inductance is done by squeezing the windings together (or if maxed out: add a turn to the coil)
Decreasing Inductance is done by seperating the windings, and try to split them as equally as possible around the Toroid (or if maxed out: remove a turn from the coil)

Following this Pattern should get you right into the Ballpark....
In my case I usually get between 4-5W @12V and 80%up Efficiency.
Not always, but most of the Time.

I even prepared a Video for that procedure, but couldn´t find the time to finish it....

73 Manuel; DL2MAN
hb9hem
 

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Re: Good results with *Rxxxx* kit?

Post by hb9hem »

Thank you so much for the instructions, Manuel & Faraaz. I will try and report back.

Result:
I did the tuning procedure on the 80m band.
Step 1. I removed one winding on L52 and then squeezed the windings a little, the resonance notch is at 2f, -66dB.
Step 2. Power went up very noticeably at lower frequencies, efficiency around 58-60%. I removed one winding on L51. Power still goes up noticeably when lowering the frequency. Efficiency peaks at 60% and then goes down a little when moving the frequency away from f - so it's basically still 58-60% efficiency.

This is odd, isn't it?
va3rr
 

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Re: Good results with *Rxxxx* kit?

Post by va3rr »

This after tuning L32 for the 14MHz 2nd harmonic. Is this representative?

Image
Slava Ukraini!
Faraaz VK4JJ
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by Faraaz VK4JJ »

I have stickied this post as it contains essential information.

I have also produced a PDF of this information (minor typographical corrections) for those wishing to have a hard copy next to them as they optimise.

https://drive.google.com/file/d/1t6T_75 ... sp=sharing
Faraaz VK4JJ
 

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Re: Good results with *Rxxxx* kit?

Post by Faraaz VK4JJ »

va3rr wrote: 15 Mar 2022, 22:08 This after tuning L32 for the 14MHz 2nd harmonic. Is this representative?

Image
Looks good.
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Re: Good results with *Rxxxx* kit?

Post by DL2MAN »

hb9hem wrote: 15 Mar 2022, 12:44 Thank you so much for the instructions, Manuel & Faraaz. I will try and report back.

Result:
I did the tuning procedure on the 80m band.
Step 1. I removed one winding on L52 and then squeezed the windings a little, the resonance notch is at 2f, -66dB.
Step 2. Power went up very noticeably at lower frequencies, efficiency around 58-60%. I removed one winding on L51. Power still goes up noticeably when lowering the frequency. Efficiency peaks at 60% and then goes down a little when moving the frequency away from f - so it's basically still 58-60% efficiency.

This is odd, isn't it?
From that point on, I would suggest to check if the measurements of the (tr)uSDX are accurate:
Please measure
1. Supply Voltage
2. Supply Current while RX
3. Supply Current while TX into 50 Ohm Dummy Load
4. Voltage PP over 50 Ohm Dummy-Load (with Oscilloscope) while TX

From this we will derive your true efficiency and compare it to the measurement, the device does.

73 Manuel; DL2MAN
hb9hem
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

Thanks for the input, Manuel.
Please measure
1. Supply Voltage: 12V
2. Supply Current while RX: 82mA
3. Supply Current while TX into 50 Ohm Dummy Load: 735mA
4. Voltage PP over 50 Ohm Dummy-Load (with Oscilloscope) while TX: 38.8Vpp (using scope probes)

And the SDR OLED says 4.81W, 56.9%.

So, my calculations would be:
TX Power draw: 12V*(0.735-0.082)mA = 7.84W
TX power out: 1/2 * (38.8V/2)^2/50Ω = 3.76W
Efficiency = 48.0%

Update: I borrowed a T connector so I can use coax instead of scope probes. Result:
Bench power supply: 12V, 82mA RX, 800mA TX, gives 8.62W
RF Out: Vpp=44.0V, gives 4.84W. Efficiency 56.1%.

All bands:

Code: Select all

		Power Supply    Out	SDR meas.	Calculated		
Band	Freq    I (RX)	I (TX)	Vpp/V	P/W	Eff.	TX P/W	RF P/W	Eff.
80m	3560	79	749	42.4	4.58	53.9	8.04	4.49	55.9%
60m	5351	80	475	36.0	3.23	61.2	4.74	3.24	68.4%
40m	7030	82	401	32.4	2.58	61.4	3.83	2.62	68.6%
30m	10106	84	489	38.8	3.74	71.1	4.86	3.76	77.4%
20m	14060	87	608	42.0	4.39	66.5	6.25	4.41	70.5%
DL2MAN
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by DL2MAN »

You know what:
I'm in the exact same situation with the *Rxxxx* Kit.
Power OK after tweaking but far away from efficient.

We're also trying to figure out what's going on.
There's only 3 possible issues:
- wrong capacitors
- bad toroids, but i could not improve it with alternative toroids.... Maybe the ft37-43 have a problem, didn't change them yet
- bad batch of bs170s even though they look legit....

Working on it. Feedback welcome.

73 Manuel DL2MAN
hb9hem
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

That's interesting. What makes me suspicious is that a few of the capacitors heat up. I can't say for sure which, my heat camera does not have sufficient resolution. I think I'll desolder some and check the capacitances.
Also: I emailed *Rxxxx* two days ago and asked whether they were sure the components are to spec - no response so far.
DL2MAN
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by DL2MAN »

Could you please specify
- which batch you have (1st or 2nd) ?
- what bands are affected by heated caps ?

I am in direct contact with them and we're trying to figure out what's wrong.

73 Manuel DL2MAN
hb9hem
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

Yes, of course.
- ordered 13 Jan and shipped 22 Feb, so that makes it B1?
- difficult to spot if coils get warm and blur everything, but I can spot small hot components in 40m and 60m, probably: C34,36-37 and C42-43.
Thanks a lot.
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Re: (tr)uSDX power, efficiency and filter optimisation

Post by DL2MAN »

OK guys, you´re not going to like this:

- We cannot give approval at this Time for *Rxxxx* Batch 1 and 2.
- There is a still unknown and unexplainable issue that causes low efficiency on all Bands
- I´m trying to work with you guys and *Rxxxx* so we can fix this and make the (tr)uSDX perfect
- The 1nF/1000pF Caps of Batch 1 are X7R Type (80/60/40m affected). This is probably why you see them heating up
- The 330pF of another Batch (Batch 2?) are X7R 50V Types (80/60/30m affected). So this will be probably even worse. But I did not see one yet, nor have I evidence to back that up.

This is partly our fault as well, as we pushed *Rxxxx* into market, when they expressed, they´d need more time and also were in the middle of moving into another workshop.
So I ask you, to please work with them and us, and try to help solving the issue without raising claims towards them.

Let´s try to be radio amatuers at it´s finest and help together here, please.

73 Manuel; DL2MAN
hb9hem
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

Thanks for getting some clarity into this, Manuel.
I guess this is just another case of commercial pressure outranking good engineering. It happens.
For my part, I'm happy to pay *Rxxxx* for good replacement parts, for example. But I'm much less happy to pay DHL their exorbitant "handling" fees. All in, shipping, fees and customs cost me 48Eur. I'm so sick of this DHL... Sorry for the rant.
TLDR; Help *Rxxxx*: Yes. Subsidize awful DHL: No.
hb9hem
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

Ok, sorry to go off topic, about this DHL, a message to *Rxxxx*:
Compared to the Chinese sellers you put yourselves at a serious competitive disadvantage by chosing DHL. Despite the much longer distances Aliexpress shipping is much cheaper than DHL. Yes, sellers on Aliexpress always lie on the customs declarations. It's not fair, but that's how it is.
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Re: (tr)uSDX power, efficiency and filter optimisation

Post by DL2MAN »

I think a few caps can be put in an envelope and shipped as letter for a few €....
But let´s not make the second step before the first....
We need to figure out what exactly is wrong.

What I can tell already: The *Rxxxx* Mainboard is totally fine. When I use it together with another RF Board (built myself) everything is according specs.
So besides the knowns issues (X7R replacements) there is still an unknown issue which is causing me more headache. Efficiency below 80% on all Bands (not just the X7R ones)
If this is solved, we maybe even get away with the X7R´s....
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Re: (tr)uSDX power, efficiency and filter optimisation

Post by DL2MAN »

OK, I´ve made a brute force attempt:
Trying to tackle the 20m inefficiency for now:
- I exchanged the T37-2 Toroids for known good ones. While this changed the amount of turns required for a certain inductance, it did not improve bad efficiency -> Maxed out at 65%
- I unsoldered, measured and replaced Shunt Capacitor C10/C11 > No Change
- I unsoldered, measured and replaced Serial Resonance Capacitor C12/C13 > No Change
Both unsoldered Caps were close to the nominal Value, and were just replaced to see if maybe there was a wrong Type used as well.
- I unsoldered, measured and replaced the BS170s -> This caused a slight change to the worse. Efficiency went down from 65% to 60%, so there might be a clue.
- In my desperation I then even swapped out the SMA Connector / Antenna Jack -> No Change
- I checked the relays, so there are not 2 active at the same time. -> only 20m relay active.
So at this point I´m absolutely clueless.


I do not have replacement FT37-42, so maybe someone could exchange those for known good ones and report back.
The only other remaining option is to also exchange Pi Filter Caps and see if it improves....
This gives me a headache....

73 Manuel; DL2MAN
hb9hem
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

I don't have any other FT37-42s, but I'm happy to order some if need be. For now, I've hooked up L15 to the nanoVNA and I'm getting about 200µH @ 50kHz but at higher frequencies the readings become silly, basically purely resistive above 1MHz. I need to check these results.
The idea was to follow owenduffy.net and maybe get some clues, obviously I expect relative permeabilities roughly as in amidoncorp's spec.
I'm happy to try other ideas, my limited stock permitting.
yo6tjj
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by yo6tjj »

Hi everyone,
first of all, thank you for the feedback and we are very grateful @*Rxxxx* for the support/ideas, understanding and patience you all took with this matter and not only. Thank you also @ManuelDL2MAN for all explanations and contributions you already done, regarding this matter.

As Manuel mentioned, we are all aware and work together with him and many of you (thanks for emails and feedback) to try to solve the PA stage efficiency matter of the kit, after the build, that was found by some of the users. Even if we do not answer the same day when you ask, we will answer next days (there are dozens of mails daily from all customers). We always try to answer and always deliver, even if there are reasonable delays.
We will get back with a solution for sure. Meanwhile, we have also published the list of parts we are using in the kits we deliver and in the assembled units, with technical specification links /datasheets. See the FAQ section on the product page:
https://dl2man.de/where-to-buy-trusdx//product/trusdx-5-ba ... assembled/

vy 73 de Andrei, YO6TJJ @ *Rxxxx*
va3rr
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by va3rr »

hb9hem wrote: 19 Mar 2022, 07:33 I don't have any other FT37-42s, but I'm happy to order some if need be. For now, I've hooked up L15 to the nanoVNA and I'm getting about 200µH @ 50kHz but at higher frequencies the readings become silly, basically purely resistive above 1MHz. I need to check these results.
The idea was to follow owenduffy.net and maybe get some clues, obviously I expect relative permeabilities roughly as in amidoncorp's spec.
I measured what I *think* is old stock #43 vs new stock #43 with a DE-5000 at low frequencies, and with a FA-VA5 at HF. Unfortunately, when I recently received my order from Kit & Parts, I mixed my old stock with my new stock and put them all in one bag :oops:

https://www.qsl.net/va3rr/xls/FT37_43_comparison.csv

You can go to the VK3CPU toroid calculator to view the difference between old and new.

https://miguelvaca.github.io/vk3cpu/toroid.html
Slava Ukraini!
6k2kus
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by 6k2kus »

The same problem persists in *Rxxxx* Batch 3, shipped on March 14.
I have constructed it and found the same problem (which led me here :)).
I also verify that small capacitors are used in the same places as above except C34.
Typically I have below 2 Watts on "favorite" frequencies and have some improvements on others: see below.

During testing I have burnt my VNA by mistake. So I have scanned frequencies by hand and found maximal power peaks. With quite equal spaced turns of core I got:

80m: 35.6 dBm = 3.63W @ 3.360 MHz
40m: 35.7 dBm = 3.72W @ 6.019 MHz
30m: 36.2 dBm = 4.16W @ 9.040 MHz
20m: 35.8 dBm = 3.80W @ 13.014 MHz
(for 60m band, I have tweaked the configuration to 15m band but due to the absence of firmware it does not work yet).
The measurement is done by TinySA + 20dB attenunator.

What is strange is they are at around the minimal frequencies in the given band but not the minima. Slighlyt above them. In all bands, the trend is the same. Maybe I can push them up using lower turns for LX2 (did you do that?), but I suspect that the power may stay the same.

Also the behavior is common on all bands: can there be a problem with other part than RF?
Last edited by 6k2kus on 20 Mar 2022, 15:53, edited 1 time in total.
hb9hem
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by hb9hem »

Regarding the FT37-43s: What I measure with the NanoVNA doesn't conform to Amidon's specs, but the FT37-43 measurements are close enough to the ones of a FT140-43 that I have around. So I guess the toroids are ok?

Image

Image
6k2kus
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by 6k2kus »

What about the coils?

There seem remain very few possibilities, given that mainboards, capacitors, transistors, toroids are okay.

I feel that you all suffer from high inductance, should we suspect the coils? If it is not only the problem of resonance but also the current flow relate to the power, the common device may be the coil.
xo3k
 

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Re: (tr)uSDX power, efficiency and filter optimisation

Post by xo3k »

For the record, my build had low power initially and less than 50% efficiency. I found that the notch was way too low on all frequencies using my VNA. So I removed 1 turn off of each notch inductor and was able to tweek them to the correct second harmonic. The power was still low (about 2 to 3 watts), so I removed one turn from each of the remaining inductors (except the 80 meter inductor where I took 2 turns off) and the power increased to between 4 and 5.5 watts per band and the efficiency was between 55 and 60 %, better but not up to spec.

Unfortunately, I later had developed a static charge that, when I touched the transceiver, discharged on the radio and killed the RX. After troubleshooting, I determined that U6 (the CL253 replacement for SN74CBT3253) was bad. Symptoms were CLK0 and CLK1 were present, the voltage on the input pin 9 was 1.4v (It probably should be 1/2 of Vcc or about 2.4v) and no response to signal injected to the cold side of C23. Even more unfortunately, my 70 year old self was not up to the task of replacement of the 16 pin chip, so I butchered the job (it works, kind of), so I will need to order a replacement main board. My advice, it's one thing to place the chips on a board with no other parts, but don't try to replace a chip on a populated board unless you have the proper tools.

Another thing, be very careful tightening the screws that hold the case together, the collars on the long side pieces of mine have already cracked through.

73, Kevin K3OX
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Re: (tr)uSDX power, efficiency and filter optimisation

Post by DL2MAN »

VA3RR might be onto something. I didn´t know there was post 2020 and pre 2020 FT37-43´s....

@6K2KUS:
This is quite normal behavior. And also: My High efficiency Rigs have more power below targeted frequency. This is because Load of the serial resonance coil goes towards 0 Ohms.
15m on the 60m Slot will not be supported. Also not in future. Please have a look at the "High Band" Announcement to see what´s possible in current Firmware.
Regarding Coils: I´ve changed the Coils on the T37-2 Toroids for known good ones. The Inductance changed, but efficiency is as low as before.

@HM9HEM:
To be honest, if it was the Ferrites, I have no clue what exact parameter would make the difference. Maybe it´s just contamination of the material used in that batch.

@K3OX
Yes, that´s the problem here: By tuning the coils, we could get the desired power, but not the desired efficiency, and we´re trying to figure out why.

My bet would still be on the FT37-43´s even though I have no clue why....

73 Manuel; DL2MAN
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