Looking in the source code file remote.c, I see that sBitx supports a telnet server on port 8081. Using the telnet client built into Windows 10, I can connect to the server about 1 time in 3. When it doesn't connect I get a message 'unable to connect'. When I do connect, the screen clears and prints "sbitx v2.0" at the top. But what can I do at that point. If I type an 'f' I get the response shown in the screen shot.
--
73,
Mark, N8ME

开云体育

Evan, I’m also noticing those inductors!!?

sBITX V2 TX problems
Have received a new sBitx V2.
RX is OK! TX no output, no matter in which mode.
PTT switches correctly!
Hardware is OK, works with software V1 without problems.
Faulty settings?
Please help
vy73 DL8DH (Hajo)

Gordon,

The early QDX kit builders (I was one) had to rework the first released boards of the QDX to remove four SMD 47uH chokes and replace them with through-hole inductors.? The reason given was that the chokes' self-resonance changed the filter characteristics.? Could that be the issue here as well?

The equivalent inductors to replace would be L202, L4, L5, L3, and L2.??

Ashhar Farhan stated that the LPF PIN diode switch design was based on Hans Summers' work.? Hans is the designer of the QDX.

I do not own a V2, so I can not verify your tests.? As stated before, the DE I have meets all FCC requirements as far as I can test.? The DE uses relays to switch the LPFs.? This would support your theory that there is an issue with the filter selection circuits.

73
Evan
AC9TU

1.? This thread has been running since Oct 6, now 15 days.? ?Many, many sets of data have been presented, including photos of the measurement setup.? ?There were initial unforced errors due to a DIODE in the Heathkit Cantenna system that added its own spurious responses.? ? The setup has been validated by (a) measurement of an Icom 718 commercial transceiver and (b) measurement of an externally filtered SN#141 sBitx V2 that demonstrated CLEAN output.
2.? ?Despite running for over 2 weeks, not a single other serial number of a production unit has been documented.? ?Perhaps I'm wrong, but I believe the ONLY production unit delivered to a customer whose output has been checked for compliance with spurious response regulations in the United States, is unit #141 -- and it is failing on some bands.? ?
3.? ?A licensed radio amateurs we are compelled to operate kits and other homebrew equipment (after some date) that comply with the spectral purity requirements.? ?The ARRL takes this very seriously and has initiated a Clean Signals Initiative

Web Page:? ?

QST article:? ?

to advance the purity of amateur transitters, specifically noting the problem with LDMOS and MOSFET amplifiers.? ??

4.? The sBitxV2 low pass filters look great in my estimation, yet the signals that I'm recording afterwards don't always bear that same excellence.? ? No one has published any spectrum of a customer-received unit otherwise.? ??

5.? I've now shown that at least ONE diode in the post-filter system appears to be generating (on one band) spurious responses (harmonics) that are above spec.? ??

6.? It appears to me that the next logical step is to isolate the amplifier output, and connect it DIRECTLY to one of the low pass filters,and then DIRECTLY to a dummy load and attenuator system for monitoring with a spectrum analyzer so that all of the associated diode switching, control circuitry, DC voltage generation circuitry, and SWR measurement can be put aside temporarily.? ? I would EXPECT that the result will generally be a "clean signal".? ?The resulting test schematic might look like this:




7.? ?If we can't fix this -- or demonstrate that these measurements have had an ERROR, or that the unit is damaged or not representative of the vast majority of manufactured units -- then I doubt we will ever get the ARRL to publish a complimentary review and this is such a fine effort that it deserves to get acclimation and approval from the ARRL.? ?Ashhar has put a HUGE amount of work into this, and deserves to get credit for his work.? ?The rest of us can pitch in to prove the outcome one way or the other.? ? ?I'm now out of town for a week and hope to get back and eventually take the next step.? ? I've learned a LOT in this process and corrected some of my measurement errors.? ?Perhaps there are others to correct?? ?Haven't seen any contradictory examples however, and able to clearly show CLEAN transmissions in at least two other instances.... so I think this needs further investigation and correction.

73
Gordon KX4Z

I’m trying to understand the receive filtering in sBitx. I’ve been studying and experimenting with Ashar’s well commented code in the function rx_process in sBitx.c. As I understand it, the incoming data along with the overlap data has undergoes a forward FFT to the frequency domain where it is multiplied by the filter coefficients. It then undergoes a reverse FFT to the time domain. However, in the time domain data the filtered audio is now in the imaginary part of the data. Why isn’t it in the real part?
--
73,
Mark, N8ME

This site’s data graph suggests that some of these diodes could work in our application. Do we just have some bad ringers?

Look at the dates on the posts.? Those are very old links that are no longer valid.

73
Evan
AC9TU

I think Carl was referring to a separate (breakout) forum just for the sBitx, not an actual breakout board.

Here's a screen recording showing this.

On Wed, Jun 16, 2004 at 03:27 AM, Ashhar Farhan <farhan@...> wrote:

.

This is what your link resolves to: https://www.phonestack.com/laptop-cho-dan-van-phong/

Evan -- so in this case, I am *using* the 10meter filter.? ? ?Its knee is at 32-ish MHz and appears to be used for 15 meters as well.? ? At least I hope I am!

These data seem to prove that we have at least a? -28dBc spur (harmonic) being formed due to the conduction of the output diode for the 10m filter!
There are likely OTHER sources, that are responsible for the remaining -34dBc 3rd harmonic.? ? ?Need to get all of this down below -43 dBc.? And for a radio of this advanced design, would be nice to have it significantly more impressive than just meeting requirements.? ?

The material I quoted cited "non linear passive components" -- is it possible that the capacitances of the reverse biased other diodes are also changing in a non-linear manner with instantaneous voltage (because the RF voltage is a varying percentage of the back biasing DC voltage) -- and that THIS is also changing the response in a non-linear manner and introducing harmonics?? ? Seems possible!? ? ?Ashhar wisely included a voltage doubler circuit, but that still means there is a significant percent change in the NET reverse bias on each part of a cycle.? ?What about either replacing the output diodes with RELAYS or using a much much higher reverse voltage?? ? ?

I just don't know exactly what next is the best step.? ? These diodes I don't think are ever switched "under load"? so a relatively modest relay could replace them.? ? at 40 watts, they should see currents only in the 1-2A range (even with 2:1 SWR).? ??

Anyone else made measurements on their V2?? ? Or have ideas?
Gordon KX4Z

Not wrong at all. I used 10Mhz, per the instructions, but using the freq counter got me quite close. Thank you.?

Again, this unit was purchased from another person. I don’t think that person made any alterations, I can’t see any alterations and nothing looks burnt

I made up a small clip lead to try to short out the diets. This is certainly not optimal, because it will act like a small antenna. But it makes an easy way to allow me to sort out some diodes ?and see what happens

So using my UHF pad, and a bunch of BNC attenuators as well, on 21.02 MHz with Drive at 84% here were the values

fundamental: -6. ?Dbm
Second harmonic: -28 DBM
third harmonic -34 DBM

these are similar to some of my previous measurements for this band which is probably the worst

applying the shorting clips to the input Diode was no improvement and maybe one Db worse

applying the shorting clips to the output diode made a 6 dB improvement at the third harmonic

fundamental: -6 dBm
Second harmonic -29 DBm
third harmonic -40 DBM

I am out of time, so I can’t do much more, but I suspect these numbers would be better with a small short rather than this large clip. However it did not completely eliminate the problem. But it’s another clue. ?

Gordon,

The voltage doubler is applied to both input and output diodes.? Maybe the 10-meter filter is turning on enough to allow the harmonics through?? Just a guess.

All,
Has anyone else seen the harmonics issue with the V2?? Ashhar Farhan has stated that all V2 sbitx are tested with a spectrum analyzer for signal purity before shipment.

73
Evan
AC9TU

Yes, thanks, Bill and Evan.
The 1N4007 is certainly not specified or intended for PIN service ; it just happens to have an intrinsic layer. Not sure how thick, and it’s one very big reason I’m concerned that it might be the cause… but a lot of my other hypothesis of turned out to be incorrecr

i’m not so worried on the input side of the filter now that I’ve looked at the filter and I am amazed at how good they are, I’m much more worried about the outside of the filter!! ?I think this might be why I never ever worried really about the harmonics on the DE. As I remember all of my writing stay were about spurious submissions, and who knows some of those might have been due to the Cantenna!! Eventually I’ll go back and check it again but I had managed to get it much better.

I think once you select the band, the diodes stay in the correct settings? I’m not certain about that. But it wouldn’t be too terribly difficult to replace the output side diode’s with relays….. just would take more space!!

yes, I did the upgrade to give more current to the diodes—-BRFORE These measurements

if folks are going to use the one in 4007 and it turns out to be the issue, then careful selection is going to become necessary.?

gordon

Gordon,

The diode you listed in your post has a max reverse voltage of 50 volts.? That is 13 volts short of the 63 volts I calculate for 40 watts in a pure resistive 50-ohm load.? I have found that all pin diodes are hundreds or thousands of dollars for a minimum purchase required to replace the eight diodes.

Maybe go back to relays for LPF selection and change the program to keep the relays on for the selected band to allow for QSK CW operation?? I believe that you did this for your DE.

Another chain of diagnosis might be the voltage doubling circuit (as you pointed out in a prior post).? There may be an issue with the doubler voltage not being filtered enough, or the capacitor is on the high side of the ESR spec.

As I have stated before, I am NOT an RF engineer, just an industrial controls engineer tinkering with radio stuff.
73
Evan
AC9TU

Alsa is always there (it is the driver + userland support). Bookworm uses by default pipewire (on top of alsa), but you can just remove it if it causes trouble.

- Rafael

Didn't Bookworm change the sound system?

Is alsa supported anymore?

73,
-- Dave, N8SBE