New adventures with *Rxxxx*

[DL1DBY]

Hi all,
I had bought two batch B2 or B3 (tr)uSDXs from *Rxxxx* but not finished them due to the known problems. Now they have new RF boards which they say have a higher efficiency than the previous boards. As I had soldered all the delivered parts to the old low efficiency boards, I asked them to sent me new relays and BS170s, as removing them from the old boards is no fun. The new boards were free, but only I you ordered something else from them. For the relays and BS170 I paid a flat replacement fee of around 30 euros, I got the new boards for free as promised but additionally had to pay 27 euros for delivery. So this set me back around 57 euros (additionally to what I initially paid when I bought the two units from them).

Having build the new boards with the number of turns on all toroids suggested by *Rxxxx* (mostly one turn less than suggested by Manuel DL2MAN), the efficiency is still far from perfect: 80m = 71,8%, 60m = 69,4%, 40m = 71,1%, 30m = 68,8% and, worst of all, 20m = 60,1%. I also did the 21:3 mod on T2.

Using the efficiency optimization procedure suggested by Manuel DL2MAN, it became clear that the second harmonic was far too low on all the bands, so that I had to remove additional turns from the LX2 toroids. I did this exemplarily on the 20m and 80m LX2 toroids. On both frequency bands I got the LX2 second harmonic spot-on. But on both bands this did not lead to an improvement of efficiency, but to my astonishment to an even lower efficiency: 20m = 58% and 80m = 65,7%. Tweaking LX1 did not improve the situation, so I did not try the other bands.

This seems to indicate to me that it may not be worth the effort to get the new RF boards from *Rxxxx*, as the efficiency is still unsatisfactory. I hope this helps other *Rxxxx* builders of B2 or B3 units.

Best regards and vy 73
Dieter DL1DBY

[DD5MA]

I got two ready assembled units, one from approved chinese seller and one from *Rxxxx*.
I measured by myself the power and efficiency on both units and none is achieving 5Watts and 80% efficiency on all bands.
But I must say that *Rxxxx* unit is very close and 10 - 20% better in power and efficiency than the approved chinese seller.
Unfortunately there seems to be a lot of misunderstanding in that matter between DL2MAN and *Rxxxx*.
I hope they can solve this dispute despite the history in the near future.

vy 73 Frank DD5MA

[Dewil23]

How accurate is the efficiency reading on the rig?

73 Karlo 9A3BKF

[DL1DBY]

How accurate is the efficiency reading on the rig?

73 Karlo 9A3BKF

At the moment I cannot exactly tell how good the efficiency reading is. What I can tell is that the power output reading is the same on the (tr)uSDX and on my Oak Hills Research WM-2 power meter.

[RichardB]

The efficiency from the (tr)uSDX is not accurate. But lets explain something about it.

The efficiency is a calculation between the amount of power going into the RF PA (the BS170s) and the amount of power going out the SMA connector. The accuracy of the efficiency depends on the accuracy of those power measurements. The power going in is done by measuring voltage across a 'known' resistance and calculating power. The 'known' resistance is called 'R Shunt'. In the menu, there is an adjustment for R Shunt - menu 8.6. R Shunt is a copper trace on the PC board and its value can vary. So, for accurate efficiency reading, one has to calibrate the reading.

This means the efficiency is not a good absolute measurement.

However, it can be used as a relative measurement. It can be used to find the highest efficiency for that radio but not used to compare the efficiency between radios.

If you really understand the difference between accuracy and precision, then the efficiency reading is not accurate; it may be reasonably precise. But that is in question because in CW and holding the PTT button down, transmitting into a dummy load, the efficiency reading jumps around some. Even then, it can still be used for adjusting the Lx1 coils.

[VE3RRD]

Manuel describes how to measure actual efficiency, and how to adjust the R-shunt value so indicated efficiency is close to the actual efficiency:
viewtopic.php?p=4138#p4138

[DL2MAN]

Hi Frank,

But I must say that *Rxxxx* unit is very close and 10 - 20% better in power and efficiency than the approved chinese seller.

In order to achieve the 80% PLUS, the units need to be tuned. This cannot be done on mass production level. So it needs to be done by user: https://www.youtube.com/watch?v=qN7hHsvcNMM

Unfortunately there seems to be a lot of misunderstanding in that matter between DL2MAN and *Rxxxx*.
I hope they can solve this dispute despite the history in the near future.

There is no misunderstanding. Everything regarding them is really clear now. We recently learned about their true intentions the hard way.
They just don't know how to behave, and have proven more than once that they understand neither the license, nor the device.
They continue to have no appreciation whatsoever for the time we have sacrificed for them at no cost. This has always been a one-way street. While they gladly asked for every bit of information from us, not even the fact that there was a problem came back from them voluntarily.
On one occasion you can assume an oversight, but that runs through like a thread.
At some point, the buck stops here, and we've decided that we no longer want *Rxxxx* as part of the (tr)uSDX family.

I won´t give you all the ugly details, as they don´t deserve any attention.
But let´s draw a virtual picture in our mind:
Imagine having a guest in your house, that behaves like he owns your home. Imagine that virtual guest playing games with you, like peeing on your couch and blaming your children for it. Imagine him further to deny all that, even though you caught him with "pants down". At the same time he´s telling all your neighbors what a bad guy you are, while enjoying your hospitality. Would you allow that guest to stay, or would you kick him out of your house ?

We have passed the point of no return long time ago.
This company has mis-used our hospitality long enough and is banned from here. They are not being supported by us any longer.

73 Manuel; DL2MAN

[DD5MA]

Thanks for explanations!

Even with efficiency of "only" about 70-75% and around 4-6 Watt out it is an amazing rig.
I use it mainly only with 5 Volts USB-supply and 0.5 - 0.8 Watts out. This gives me a very good safety against burning BS170 and mismatched antennas.
Only sometimes on bad conditions I use a step-up-converter to 9 Volt and 2-3 Watt out. I like it QRPp a lot. With Digital-Modes I made astonishing QSO.
As I follow the rule - never change a good running system - I have so far no intention to made any further small improvements by myself.
But for a last word - I wonder, why an approved seller is selling a unit ready to use with efficiencies of below 70% and Power out at 3.5 - 4.5 Watt? I do expect normally that the sell an optimized unit as they did not mention that the buyer have to do it by himself.

BUT - I am very satisfied with your impressing design and do not want to miss it.