(tr)uSDX Forum

Posted: **26 Jun 2022, 00:42**

Hello All,
I have spent two days working on my ASSEMBLED tr usdx from the authorized seller Uellyqh on ebay.
I measured the current draw on receive and subtracted that from the transmit draw. I then measured the
PP voltage with my tectronix scope. Did the math and got the RF out on all bands. Did more math and got the efficiency. Guess what? The Tr usdx displayed numbers were very close to the math results. So I am happy the sweet little thing is quite accurate with the 17 shunt. HOWEVER, my efficiency numbers are not good.
At 12v: At 13.8v:
80 meters 4.71w @68 % 80 meters 6.24w @69 %
40 meters 4.09w @62 % 40 meters 5.36w @62 %
20 meters 4.04w @55 % 20 meters 4.75w @52 %

The rf output is ok but where are the high efficiency class E numbers? So far I have adjusted the filters to "spot on", rewound T2 as suggested, tried many different cores/windings for L15 even a binocular core with no real change in efficiency. I am out of ideas. I suspect that possibly my rf board was built with inferior quality caps. I am willing to change them but I am uneducated in what size/type/quality I need.
If that data is available I would appreciate being directed to it. Please advise if I missed something.
Thank You.

Posted: **26 Jun 2022, 07:53**

Hi.
I recently modified a low band RF board to the classic bands. This means removing every cap in the tuned circuits and starting again. The capacitors are 0805 size NPO /COG rated at least 100v and 1% tolerance. I bought the capacitors from Mouser and each type a minimum of 10, the price adds up though. There were actually a couple out of tolerance which did not get used. The capacitors were Yaego manufacture. Replacing these capacitors is not easy and you need good magnification, a small bit on your iron and it has to be temperature controlled, too cool means the component is heated too long and too hot can cause multiple issues.
The other issue was some of the specified values have a lead time of 18 months, I did shop elsewhere but 300 and 130pf were very difficult, I did eventually plump for 270+33pf and 100+33pf which worked OK. On setting up the toroids I got the second harmonic filters set up fine but on one band efficency was bad which was caused by a new cap going open circuit after fitting.
Results using external testing and the efficiency readout didn't match and I had to change the shunt to 18. Now both tally up closely about 1 to 2% of a discrepancy.
Hope this is of some help.

Posted: **26 Jun 2022, 13:08**

Thank you for your response. How was your efficiency after you finished?
I looked at mouser and digikey caps last night but I could not find the needed values. I suspect the kit makers are having similar issues and boards with less that quality caps are slipping out.
Thanks again for your info. By the way I have done surface mount with my temp controlled weller before with great success. With a Dremel tool I made a tip perfectly sized for the 0805 caps that does a nice job.
I would rather have a Classic RF board, 80,40,20,15 and 10. Maybe when they are commonplace, I will buy that and have better luck.

Posted: **26 Jun 2022, 19:00**

LearningLots wrote: ↑26 Jun 2022, 00:42 Hello All,
I have spent two days working on my ASSEMBLED tr usdx from the authorized seller Uellyqh on ebay.
I measured the current draw on receive and subtracted that from the transmit draw. I then measured the
PP voltage with my tectronix scope. Did the math and got the RF out on all bands. Did more math and got the efficiency. Guess what? The Tr usdx displayed numbers were very close to the math results. So I am happy the sweet little thing is quite accurate with the 17 shunt. HOWEVER, my efficiency numbers are not good.
At 12v: At 13.8v:
80 meters 4.71w @68 % 80 meters 6.24w @69 %
40 meters 4.09w @62 % 40 meters 5.36w @62 %
20 meters 4.04w @55 % 20 meters 4.75w @52 %

The rf output is ok but where are the high efficiency class E numbers? So far I have adjusted the filters to "spot on", rewound T2 as suggested, tried many different cores/windings for L15 even a binocular core with no real change in efficiency. I am out of ideas. I suspect that possibly my rf board was built with inferior quality caps. I am willing to change them but I am uneducated in what size/type/quality I need.
If that data is available I would appreciate being directed to it. Please advise if I missed something.
Thank You.

Where did you buy your (tr)uSDX from?

Posted: **26 Jun 2022, 20:40**

LearningLots wrote: ↑26 Jun 2022, 00:42 Hello All,
I have spent two days working on my ASSEMBLED tr usdx from the authorized seller Uellyqh on ebay.

Posted: **27 Jun 2022, 08:07**

Hi,

It is very very unlikely, you got a Unit from Sunny with wrong caps. They are produced in Batches and I have a sample of every Batch here, which works just fine.
My best guess would be faulty external measurements....

I invested in a calibrated DMM to measure Voltage and Current.
Especially current measurement is tricky, as it usually involves Voltage Drop over the internal shunt path, which then causes lower Output Power. While you assume, you have still the lets say 12V of your Power Supply, in reality it might be 11,8V behind the DMM.
So IF you´re measuring Current, measure Voltage with a second DMM at the same time at the rig (not at your power supply).
Second big problem is usually the (lack of) Accuracy of the consumer type SWR/PWR Meters, that needs a certain minimum Power (like eG 1W) to show something at all, and between 1-10W usually very inaccurate (Like 10-20% error)
Using those Numbers can get you on the wrong path.

I measure Voltage Peak-Peak over Dummyload with Oscilloscope. That´s the most accurate way of determining output Power, I have here.

If you have a very recent assembled rig, we´ve determined RShunt 22 to be accurate for the latest Batch 3.

73 Manuel, DL2MAN

Posted: **27 Jun 2022, 12:08**

Thanks for your reply.

As stated above, I made my RF wattage measurements using my Tektronix scope measuring PP at the dummy load.
I do have several watt meters but do not rely on them due to the limitations you mentioned. Because my analog scope does not digitally display the PP voltage and has to be measured by looking at the trace, I agree there is some possibility of small error.
I am measuring the total current draw and receive current draw at at the radio connector with a Fluke 77 meter.
I have no idea how to measure and check the shunt nor do I even know where it is on the board. I only compared the display wattage readings and efficiency readings with my measurements and math.
You are correct that I used the voltage readings at the power supply. I will redo everything and make my voltage measurements at the radio.
That you so much for your patience and guidance. This 75 year old can use all the help I can get.

Posted: **27 Jun 2022, 12:15**

What model Tektronix scope and what is its bandwidth?

Posted: **27 Jun 2022, 14:46**

My scope is a Tek 2213a 60mhz bandwidth, which should be plenty for the hf signals I am looking at.

Posted: **28 Jun 2022, 00:53**

Hello All,
Today I remeasured everything with the DC metering done at the radio connector. I also remeasured the RF envelope with my scope and here are the results for my bands of interest 80/40/20.
80meters Rec draw 79.3ma. Trans draw 690ma. Minus Rec=610.7ma x 11.9v=7.267 DC watts.
Scope PP=46V squared=2116/400=5.29w/7.267=72.79% 17 shunt display =5.06w 66.58% eff. 18 shunt display=70.5% 19 shunt display=74.4%

40meters rec draw 79.3ma. Trans draw 700ma. Minus rec=620.7ma x 11.9v=7.386 DC watts.
Scope PP=44v squared=1936/400=4.84w/7.386=65.5% 17 shunt display =4.70w 61% 18 shunt display=64%
19 shunt display=67.5%

20meters rec draw 79.3ma. Trans draw 680ma. Minus rec=600.7ma x 11.9v=7.148 DC watts.
Scope PP=42v squared=1764/400=4.41w/7.148=61.69% 17 shunt display=4.39w 60.42% 18 shunt=62.1%
19 shunt=65.9%

It looks like an 18 shunt would be closest to actual measurements on my board. However the efficiencies are still not what I expected and fall short of the advertised data.
Since Manuel DL2MAN has a high efficiency RF board from each batch, I would love to buy one from him and get myself out of this hole. Pretty please?

Posted: **28 Jun 2022, 07:36**

LearningLots wrote: ↑28 Jun 2022, 00:53 (...)
Since Manuel DL2MAN has a high efficiency RF board from each batch, I would love to buy one from him and get myself out of this hole.(...)

I don´t sell my samples. Every of my boards also started somewhere, then I tuned the Filter Boards, and they went efficient.
So you checked your measurements, now it´s time to tune the filters.
Please watch this Video:
https://www.youtube.com/watch?v=qN7hHsvcNMM

73 Manuel, DL2MAN

Posted: **28 Jun 2022, 14:09**

Manuel,
I have watched that video 20 times. I have tuned my filters again and again. The efficiency numbers I posted last are the best that I can get out of this board.
I have used my nano vna to tune, I have also used my HP 8596E spectrum analyzer to tune the filters while the radio was powered and working, and the tune I now have is the best I can get. For the record I have only tuned 80/40/20. I don't care at all about the other bands.

Posted: **28 Jun 2022, 18:07**

Hi.
I think you need an infrared camera to see if any caps or toroids are running warm and reducing efficiency. I used very slightly thicker enamelled copper wire eventually on my conversion and this did make a difference especially on L15. I also did the SWR transformer modification, all added up to over 80% efficiency and good power on all bands.

Posted: **28 Jun 2022, 19:19**

Hello Murphy310,
I have followed your postings concerning the changes you have made with great success!
I too changed L15 and tried many things including thicker wire ( which is on there now) I also added turns to increase the inductance, I tried a binocular core, and saw little change in efficiency. At one point I soldered gold machined pins where the coil connected and I was able to quickly plug in many coils. That kept things easier on the copper board. I did the 1/7-- 2/14 --3/21 transformer modification and actually got better efficiency with the 2/14. No idea why.
I have monitored my signal using an HP spectrum analyzer and an -50db RF sampler at the dummy load. My harmonics are way down and all looks good. Frankly I first thought the efficiency numbers were just way off and the radio was actually doing OK. But after my repeated measurements it looks like the radio is very close to my measurements when using the 18 shunt. So be it.
I'm an old man and have just about run out of steam with this problem. I can easily live with the performance it is giving me and some day would like to try building the classic board. With all the problems getting caps now, that classic board will have to wait.
I am grateful to you and Manuel and others for all your suggestions.
Thanks again.

Posted: **28 Jun 2022, 22:01**

Hi LearningLots,

Murphys suggestion would in deed be my next (Thermal Camera). If you tell us where you live, maybe we find someone nearby you, who can support you on this.

73 Manuel; DL2MAN

Posted: **28 Jun 2022, 23:28**

Hello Again,
Thanks for your continued efforts to help me.
I live in Largo Florida, USA. Largo is near Clearwater and St. Petersburg Florida.
My ham call is N2LZV

Posted: **29 Jun 2022, 05:32**

What are people using for a "thermal camera"? Search Amazon and it's hundreds of dollars, check out fluke and it's thousands! Not exactly my "price point", is there a ham friendly alternative?

Posted: **29 Jun 2022, 08:18**

Ohwenzelph wrote: ↑29 Jun 2022, 05:32 What are people using for a "thermal camera"?

I´m using a relatively cheap SEEK XR, from years ago. This is a thermal Sensor to be connected to your Smartphone or Tablet.
This seems to be the successor:
https://www.amazon.com/dp/B07RQ3J27Y/re ... QUWERDQZF
This is an alternative Supplier of a similar conecept:
https://www.amazon.com/-/de/dp/B0728C7K ... rd_w=iURqY

This is enough for the job....

73 Manuel, DL2MAN

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