(tr)uSDX power, efficiency and filter optimisation

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absteen
 

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Joined: 06 Oct 2022, 23:29

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

Post by absteen »

Hello all.
Name is Andrew, and call is K6STN.
A great deal of information here regardig the inductors.
I will cut to the chase.
L11, L32, and L41 are correct for vallue according to my colleage ND6T.
By careful measurment he found that those 3 inductord were almost spot on for the listed value.
All other inductors however were 1 turn "heavy" and reducing the # of turns accordingly brought them down to very close to listed value.
He states his radio acheived full output on all bands (Lo band board)
While I trust his knoledge and skills implicitly, I of course must find out for myself.
I built a similar jig to use with the Nano VNA and the 3 coils in question are very close to stated value.
My only question is; has there been any design chages that would require a higher value of inductance than shown on the schematic/
S58J
 

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Joined: 31 Dec 2021, 13:08

(tr)uSDX power, efficiency and filter optimisation

Post by S58J »

Hi

After many months of checking and changing components on my RF board I am slowly loosing my faith. I've built my (tr)uSDX from scratch by ordering bare PCBs from JLCPCB, ordering the finest parts (i.e. capacitors) from Mouser. I have tested two different versions of FT37-43 (starting from Amidon, later to Fair-Rite). I went the length of testing different FETs (from FTD86256 to IRLML2060, of course with proper filter capacitors to each respective FET), changing the number of toroid turns on each respective band and on L15 (20, 22, 24) .... I compared filters to my previous very successful uSDX builds (the 5-band and 8-band versions)... but no change. I even compared the T2 behavior (from 7/1 turn to 21/3 turns to end up with 14/2 turns) - no change.

What ever I did I always end-up arround 50% efficiency and between 2,5W to 3W output. The SWR is always 1:1.1

So, with all my humongous respect to Manuel's amazing work, may I humbly ask: is there a possible issue related to RF PCB design?

As stated I ordered PCBs from JLCPCB (using Gerbers from Manuel) and the (tr)uSDX Mainboard works from the very first power-on. Also my previous two uSDX work from their very start.

Kind regards

Janez, S58J
HB9HJF
 

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Location: Zurich, Switzerland

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

Post by HB9HJF »

Janez,

Given that a significant number of people have built up the transceivers and get efficiencies near 80% and power output of ~5W at a bit over 12V on the low config and efficiencies near 70% and ~5W output on the high config, it's fairly clear that the design has been proven in the field.

It is also clear however that there are people that have problems with their examples for various reasons, mostly either substandard PCB manufacturing or poor build components/practices when constructing. (This is not a judgement on your construction or components, just a generic observation.)

Have you been using a NanoVNA or similar to gauge the peaks of the filter toroids to get the coils set correctly?
Are your T1 and T2 correct for winding direction?
How are you measuring your output power?
How are you measuring your DC input power?
What's your input voltage? 3W radio out for 11.2V (x3 Li-ion cells) is entirely expected and good enough. 13.8v may give you five to six watts of output at a risk of toasting your FETs.
Are you still getting a half watt or so on USB power alone?

I was having difficulties getting useful efficiency readings until I realised I had a methodology problem in my reading from my Rigel. Once I fixed that, I was able to get much more accurate and repeatable output power numbers. My efficiency readings are not as accurate as I'd like as my current meter doesn't read to thousandths of an amp. But, I've been able to get "good enough" readings to make sense.
Also, watch for having possibly cooked some components with an iron set too hot. It's a possibility.

(edited for spelling and grammar)
Last edited by HB9HJF on 12 Dec 2022, 22:27, edited 1 time in total.
-- Cathal Ferris.
Paddler, pedaller, stargazer, nerd.
Wiggler of electrons both in silicon and in the ether.
DL2MAN
 

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

Post by DL2MAN »

S58J wrote: 03 Dec 2022, 11:19 So, with all my humongous respect to Manuel's amazing work, may I humbly ask: is there a possible issue related to RF PCB design?
(...)
Janez, S58J
I can say with confidence:
No, absolutely no chance. Rev 1.0 of the PCB Layout is unchanged since release and there are now over 5000 Units in the wild. I think we would have noticed a PCB error by now.
But there might be a chance, that your specific pcb is damaged.

What´s the source ? If you want to fix it, you need to be logical:
1. SWR and efficiency measurement doesn´t work: Try to fix that before trying to optimize efficiency.
2. When working on efficiency, also consider the Toroids (T37-2 the red ones) as source of the problem. Easiest way to figure out where you´re losing energy is by thermal camera....
Break down your big problem in multiple, smaller problems, that will be easier to solve. Then eliminate one after another. Maybe even buy a completed rig from Sunny for comparison measurements.

73 Manuel; DL2MAN
Luca66
 

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

Post by Luca66 »

Hello everyone, I'm turning to anyone with a request regarding filter optimization. I'd like to understand, even through some explanations, how the acceptable trend of a filter should be after the fine-tuning of the spacing of the windings. In general, I understood how the trend of the curve should be, but I didn't understand what the tolerances are to accept it as valid. 73 and Merry Christmas.

Update
I add some pictures to clarify my request. They concern the setting up of the second harmonic filter for the 20 m band. One on rf board Hi and one on rf board Lo. Are both acceptable?
Hi bands 20 m
Hi bands 20 m
Compress_20221225_222240_0730.jpg (95.41 KiB) Viewed 7011 times
Attachments
Lo bands 20 m
Lo bands 20 m
Compress_20220522_085756_6145.jpg (128.84 KiB) Viewed 7011 times
oe3whu
 

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

Post by oe3whu »

Hi Folks, is there any source for the filter inductor's values. Not the winding turns but the uH /nH values ?

I ask because my power on 20m is significantly below the one on the other bands (1.5 - 2.1 W compared to 3.4 -4W !! i'm using 11.4V supply from 3 LiPo's)) .
I tried to change frequency to determine the optimum frequency for power out .. and it is abt 12.8 Mhz (Measurement thank's to the fact that truSDX doesn't care abt band limits for transmit :-))
At 12.8 Mhz i'm getting 4.1 W
As i rather want to measure the values and align it out of the circuit, Values would be helpful (By the way i'm using the "classic bands" RF board)
dl6sez
 

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Joined: 30 Dec 2021, 22:54

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

Post by dl6sez »

Hello OM,

as expressed many times here in the forum, you still have to adjust the toroid windings to your FETs! Not all FETs are the same, so it would not be really ready if you measure and adjust the Inductors without the FETs. Yes for the harmonic notch a value with measurement could bring you to the desired number of turns, but also has to be tweaked in the circuit by pressing the turns together or wider the distance.....
So if you see that your actual point of match is 12.1MHz simply remove 1 turn from the toroid nearest to the antenna and measure again.
Best method is the VNA supported adjustment as described above for harmonic notch, than you can measure again and remove or add one turn to the toroid nearest to the PA FETs.
It will not make your adjustment faster if you measure the inductance.
I once thought as you and learned on my uSDX (the former version of the (tr)uSDX) that it makes no sense to measure the inductance althought i also tried it with a very good inductance meter.
The values should be somewhere in the forum, there was a table made when DL2MAN added High and Classical bands.

73 de Chris
Chris DL6SEZ, JN48XL near Ulm, Southern Germany
oe3whu
 

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Joined: 02 Apr 2023, 14:10

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

Post by oe3whu »

Hi Chris, thanks for your reply. Sorry for having not read all the relevant posts. Finally i started exactly as you proposed. Has been a tough job. But after 2 hrs i'm getting now 4W on all bands with my 11.4V
:-) WOlfgang oe3whu
p.s. made also the mod to prevent the audio from howling .. can recommend that heavily !
LILO
 

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

Post by LILO »

DL2MAN wrote: 22 Jun 2022, 10:53 In Sunnys Lot 3 (built with T2 Mod 3:21), we found that PWR measurement was also 0,3-0,5W Off from reality -depending on Band.
What could be the cause of that?

I'm in process of building Classic rf board from Uptech kit. Currently bands 10 and 15 are built and tuned. With Rshut value of 20 displayed efficiency is around 70% which corresponds to external measurements. But displayed power is 0.4-0.5W lower than real values. Not a critical issue but just curious why?
Ohwenzelph
 

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Joined: 01 Jan 2022, 03:47

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

Post by Ohwenzelph »

How does one optimize the filters/spacing on the toroids if one does not have a NanoVNA?
DL2MAN
 

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

Post by DL2MAN »

Ohwenzelph wrote: 25 May 2023, 01:45 How does one optimize the filters/spacing on the toroids if one does not have a NanoVNA?
Answer is simple: Buy a NanoVNA. You can get them for around 50€ (sometimes even for 30€) and you can use them for much more than just filter tuning. eG Antenna optimizing. This is a valueful, inexpensive tool, that every HAM needs IMO.

73 Manuel; DL2MAN
DL2MAN
 

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

Post by DL2MAN »

LILO wrote: 24 May 2023, 15:41 What could be the cause of that?

I'm in process of building Classic rf board from Uptech kit. Currently bands 10 and 15 are built and tuned. With Rshut value of 20 displayed efficiency is around 70% which corresponds to external measurements. But displayed power is 0.4-0.5W lower than real values. Not a critical issue but just curious why?
To be honest: I have no clue. Probably component tolerances. Be it ADC, resitors or even Traces and Connectors.

73 Manuel; DL2MAN
H4wk
 

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Joined: 08 Jul 2023, 16:53

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

Post by H4wk »

could someone explain why we tune for second harmonic? I have observed that the high peak corresponds to low swr so wouldn't the be where you have the highest resonance? maybe a dumb question but this is my first kit and my first hf radio as i am broke and this little guy is super portable and capable
texan
 

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Joined: 23 Oct 2023, 20:15

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

Post by texan »

I just received an assembled unit from the web store(newdiytech). With 5v over USB I am seeing ~.5w, but with 13v from battery am only seeing 1.1-1.8w. Operating upper side band. What should I be looking at?
dd_ly
 

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

Post by dd_ly »

Hi all, I'm new to the forum and appologize if I have not read something yet. However, I received my kit and since this power/efficiency topic seems all around I did some LTspice work to understand the circuit. In assition looking at the datasheets I spotted a detail on the BS170 that seems important.

From simulations with an ideal switch as well as the BS170 model it turned out that RDSon is importent for power as well as efficiency. The gate is driven from a 5V source and therefore we operate in the red marked area.
DS_RDSon_vs_VG.jpeg
DS_RDSon_vs_VG.jpeg (58.08 KiB) Viewed 3152 times
As soon as we have some current the RDSon may be in the range of 2Ohm or something. In simulations I did with the BS170 model I could barely reach 3Watt and 75% Eff when the Transistors are driven with 5V and below. Increasing the drive voltage to >6V did solve the issue at least in the simulation.

So, this is pure theory and needs prove in the practical circuit. I will not have my sample build up so soon but may be somebody can try to increase the drive voltage.

73 dd_ly
Last edited by dd_ly on 11 Nov 2023, 18:25, edited 1 time in total.
dd_ly
 

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

Post by dd_ly »

When you rise the +5V from an external power supply slowly to eg. 5.3V, This should still be ok and if my idea is correct it should already have a visible influence.
dd_ly
 

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Location: Germany / Saxony

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

Post by dd_ly »

Same issue for the FDT Transistor:
DS_RDSon_vs_VG_FDT.jpeg
DS_RDSon_vs_VG_FDT.jpeg (75.51 KiB) Viewed 3146 times
That would fit to the observation that this transistor always performed worse.
dd_ly
 

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

Post by dd_ly »

Please find attached the LT schematic in case you like to play yourself. It calculates in, out power and efficiency. After running the sim you can make this visibla by clicking view/error log.
I put this data in a table. In simulation I get the 80% at 5W only with 6V gate voltage:
BS170_eff_vs_Vgate_vs_L.jpeg
BS170_eff_vs_Vgate_vs_L.jpeg (95.23 KiB) Viewed 3141 times
I wonder if you can see this effect here in the gate voltage behaviour. When the transistor is open at insufficient drive voltage a cut off effect becomes visible. I marked this yellow.
LTspice.zip
(2.03 KiB) Downloaded 126 times
Again, this is simulation and not proven knoledge. I hope it helps to get forward. What I also see is that BS170 is operated close to spec limit. It may make sense to use a stable 3W solution for now instead of having 5W for some hours until the wind moves the endfed wire and invreased VSWR kills the PA.

Also do not take the coil turns to serious. It is just using the AL-value.

73 dd_ly
Attachments
transistor_cut_off.jpeg
transistor_cut_off.jpeg (80.73 KiB) Viewed 3141 times
dd_ly
 

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

Post by dd_ly »

Hi, sorry for all the typos, unfortunately I can not edit the posts any more.
However, when somebody does the experiment with a small increase of the 5V supply please check also the quality of the SSB signal. At the moment I have not really understood what the mechanism is, to get this from the DDS chip to the final RF.

The experiment would have the following steps:
1. Measure exact 5V supply as it is when 12V us available from outside.
- determine out power and efficiency
- Check SSB signal quality, eg. with an SDR waterfall
- if possible create an oscilloscope screenshot for the BS170 drain voltage

2. increase to 5.3V
- determine out power and efficiency
- Check SSB signal quality, eg. with an SDR waterfall
- if possible create an oscilloscope screenshot for the BS170 drain voltage

3. please post your results here

The driving 74ac00 gate as well as the BS170 is manufactured by many different manufacturers and when we look over the results for many different boards the tolerances of the following components get combined:
1. 74ac00
- drive strength
- transfer delay for both edges
2. BS170
- Vgs typical 2.1V but can vary from 0.8 to 3.0! (lower should work better)
- RDSon typical 1.2Ohm but can be up to 5 Ohm! (less is better)
- Ciss typical 24pF but can be up to 40pF (slow down in switching time)
3. Inductor Q
Refiry
 

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

Post by Refiry »

I've learned a lot.
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