?Je to dobrá zpráva pro v?echny ?ekající. Není pot?eba kolektiv HF Signals nutit ke spěchu. Dělají, co mohou aby v?e bylo v po?ádku a osazení desek, kompletace a testování se nedají nijak uspěchat bez zhor?ení kvality. Proto na ně netla?me a ?ekejme, na v?echny se dostane. Snad by mezitím mohl b?t ke sta?ení nějak? manuál nebo instruktá?ní video, jak TRX správně nakonfigurovat nebo provozovat. Také se sice nemohu do?kat ur?itě v?borného TRXu, kter? je brzy na cestě k nám. Lev OK2PLL
Vypadá to, ?e se obrázky v první zprávě nevykreslily správně, tak?e zde je repost:
V?ichni jsme p?ipraveni za?ít dodávat jednotky zBitx v dávkách od p?í?tího t?dne a zákazníci by měli obdr?et va?e sledovací ?íslo, jakmile bude jejich jednotka p?ipravena k odeslání.
Mezitím jsme vám chtěli p?edstavit zBitx a nabídnout vám pohled na v?robu zBitx, abyste mohli ocenit práci a úsilí, které je do v?roby těchto rádií vlo?eno.
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Zde je krátké video zBitxu v akci:
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https://youtu.be/3NSLHjw3Egg Rádi bychom se s vámi podělili o některé novinky z montá?ní linky zBitx v na?em závodě v indickém Hyderabadu.
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Jakmile desky dorazily, t?m se pustil do montá?e. Spojují v?echny díly s pr?chozími otvory, jako jsou cívky, konektory, regulátory, headery atd.
Tyto desky byly poté p?edány dal?ímu t?mu, kter? p?ipájel IRF MOSFETy a namontoval je na zadní panel, kter? slou?í jako chladi?.
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Zatímco to probíhalo, jin? t?m za?al pracovat na desce displeje a p?ipájel displej, Raspberry Pico, kodér, konektory a reproduktor.
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Jakmile byly zobrazovací desky dokon?eny a integrovány s RF deskou, pro?ly kolem mechanické a elektrické kontroly. Jakmile to bylo hotovo, desky byly p?ipraveny k ohradě.
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After testing, the radios were packed along with the test report and kept ready for dispatch.
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The dimensions of the radio are 139x84x37mm and weighs about 385 grams without the 18650 batteries and about 485 grams with batteries.
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Since there was a lot of confusion about the 18650 batteries for the zBitx, here is a photo of the batteries we used during testing. They do not come with tabs and are flat topped. Please note, batteries aren't included in the package.
I have finally disassembled my sBitx fully and removed final MOSFETs.? I have to cut the away to not damage the PCB. One of the was still alive (so I'll probably use it for prototyping):
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But the second is broken (probably due to overheating):
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So it looks like a fan is the "must have" if one wants longer continuously work in digital modes.
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Now I have to decide if I should mount the new MOSFETs and reassemble the device as it is, or wait until the new aluminum-nitrid isolators arrive.
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I'm also afraid about the PCB state when replacement of finals may repeate multiple times. It seems that the pads of Q16 and Q17 are quite delicate. If they are gradually damage during replacements, at ID reaching 4 A (or even more in a pulse) the PCB may gradually deteriorate and finally fail.
On Fri, Feb 28, 2025 at 10:57 PM, JJ - W9JES wrote:
I think some folks misunderstood what I was asking for.?
The sBitx V2 has IRFZ24N MOSFETs. We want to continue to use them for the finals. What mods have to be performed to prevent oscillations and early MOSFET failures?
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Thanks.
No documentation was sent about any changes to the v2.
What happened was that the devices sent in April 2023 did not come with any information sheet, so on May 3rd, several messages came, which can be found on the sbitx.net page, how to set the performance and some similar information. The hardware modification was discussed on the forum and no information was released about the change.
So whoever modified it did it according to their own thoughts.
My own experience with the v2, which uses IRFZ24N FETs in the output stage:
1. I checked the electrical and mechanical connections of the device and repaired them as necessary. (FET clamper broke / D27 diode was faulty, so I replaced the power/swr diodes together / Bias adjustment was difficult, so I modified the circuit (see F5NPV website) / I replaced the mica insulator with Aluminum Nitride for better heat conduction / I cool the power stage heatsink with an external 92x92x25mm silent fan / I cool the RPi4 from the back with a 50x50x10mm fan fixed on an intermediate board / I use the PTT control of the power stage based on the designs of KX4Z Gordon Furthermore
2. I use the device with a current limit of 12.5V and 6.5 A, because it was not in use yet and I powered it from a battery, with a dummy load instead of an antenna, then one of the FETs of the power stage became shorted. The replaced and selected FETs have been working fine ever since! Currently more than 8800 QSOs and these FETs have 168/150 dxcc/lotw since November 16, 2023.
3. I use a single antenna on 3 bands. This is a vertical delta loop antenna installed obliquely. There are two ferrite rings at the feed point (about 10 meters high).
One is for 100/50 Ohm and the other is for symmetrical/asymmetrical impedance matching. I sized the 42.8 meter wire to 7 MHz, which can also be used at 14 and 21 MHz without an antenna tuner.
4. I consider myself a returning amateur radio operator because of sbitx, because I previously dismantled my antennas (2 el 5 band QQ, 20.8m high vertical) and I made this antenna only for sbitx, so that I could use it.
5. Most importantly, if it weren't for the amateurs who brought the development to the current level, I probably wouldn't be a device owner.
So a huge thank you to them for their continuous efforts to fix the bugs they find.
I suggest verifying that adjusting the PABias1 pot does change the voltage on the MOSFETs' gates.? As Gordon stated, you need to be careful when making this adjustment.? It is very easy to drive the MOSFETs to destruction, and the current will "jump" as you get close to the nominal setpoint.
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A safe way to test the bias control is to measure the resistance from the MOSFETs' gates to ground without power connected.? You should be able to vary from almost zero ohms (55 ohms) in the fully counterclockwise direction to nearly 10k ohms when fully clockwise.? Be sure to return the control to the fully counterclockwise position before restoring power.
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In addition to a faulty control, one of the bypass capacitors may be shorted.
I suggest verifying that adjusting the PABias1 pot does change the voltage on the MOSFETs' gates.? As Gordon stated, you need to be careful when making this adjustment.? It is very easy to drive the MOSFETs to destruction, and the current will "jump" as you get close to the nominal setpoint.
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A safe way to test the bias control is to measure the resistance from the MOSFETs' gates to ground without power connected.? You should be able to vary from almost zero ohms (55 ohms) in the fully counterclockwise direction to nearly 10k ohms when fully clockwise.? Be sure to return the control to the fully counterclockwise position before restoring power.
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In addition to a faulty control, one of the bypass capacitors may be shorted.
one of
the ports is for power, I don't think it provides data.
On Fri, Feb 28, 2025 at 5:06?PM Ken N2VIP via
<ken=[email protected]>
wrote:
The RPi Zero 2
W has two USB 2.0 ports, I guess you could use an
interposer board and include a USB-C connector, but
it would only work at USB-2.0 speeds and increase
the size of the radio.
Those two diets you were talking about are not normal diodes they are transient voltage suppressors. They won’t conduct until the voltage gets around 10 V.
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Be very careful with that PA bias. You can easily destroy the transistors with that. ?Turning it too far will cause the bias current to go to many amps!!
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The strange thing is that performing the bias regulation (as described on the website) I couldn't get the increase by 200 mA in the whole range of regulation.
Those two diets you were talking about are not normal diodes they are transient voltage suppressors. They won’t conduct until the voltage gets around 10 V.
Be very careful with that PA bias. You can easily destroy the transistors with that. ?Turning it too far will cause the bias current to go to many amps!!
There is some odd residue near the input of your output transformer. ?
On Feb 28, 2025, at 19:39, Gordon Gibby KX4Z via groups.io <docvacuumtubes@...> wrote:
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be certain that you have correctly identified the PA bias potentiometer. It would be very odd if turning that too far didn’t destroy the MOSFETs
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when you press push to talk the voltage on L 80 and L 81 should go up— because it is controlled by Q9. if Q9 is continuously on, then you have blown a different MOSFET, one or more in that complicated switching system around Q9. ?You might want to figure out for sure if you really can’t see switching action going on there.
be certain that you have correctly identified the PA bias potentiometer. It would be very odd if turning that too far didn’t destroy the MOSFETs
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when you press push to talk the voltage on L 80 and L 81 should go up— because it is controlled by Q9. if Q9 is continuously on, then you have blown a different MOSFET, one or more in that complicated switching system around Q9. ?You might want to figure out for sure if you really can’t see switching action going on there.
I agree with Gordon's suggestions.? IRF520 would be a more robust part, and the TVS protection is a good idea as the driver circuit can deliver higher than the gate voltage if driven to full power.
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Also, Joel suggests that the pin diode current should be increased by 470 to 330 ohm replacements.? The bias increase is another good idea.
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Another suggestion is to add the resistors to the drain of Q101 and series with D20 and D21.? Gordon posted this here:
On Fri, Feb 28, 2025 at 5:06?PM Ken N2VIP via <ken=[email protected]> wrote:
The RPi Zero 2 W has two USB 2.0 ports, I guess you could use an interposer board and include a USB-C connector, but it would only work at USB-2.0 speeds and increase the size of the radio.
Unknown. I heated the end closer to the back of the PCB, and the cap fell right off the board, with a end still on the PCB. A check of the cap shows it is open, not surprising with the end missing.
Anyway, I found a 0.1uF cap in the junk box, just a tad too big, Hi Hi, to put in on the board, but connecting it to the board gives me LOTS of audio again. When replaced with an appropriate cap I'll be back in business. Then to calibrate the BFO, frequency, etc. And have it on the air again.
73, Richard AG5M
On Friday, February 28, 2025 at 02:25:59 PM PST, tomekdm sp7etd via groups.io <tomekdm@...> wrote:
Interesting why it cracked/failed... due to mechanical stress, like bent of PCB... temperature shock...? or was it already bad since new...
If C202 (47pf) SHORTED, you would expect potentially what is being seen.
If the 80 meter filter were invoked, and your frequency is above that, the input of the filter might act like a short.
If D15 shorted, this could happen, or if Q24 shorted this could happen
If the teflon insulation on the orange wire melted (this is not likely) then the output of the transformer might be shorted
If the antenna output connector or coax shorted, this low output might happen.
But chasing down every one of those is very time consuming.? ?Again, it might be easier to just look at what is coming out of the orange wire, disconnected from everything else.....much simpler than all the other techniques.
Anyone see something better?
Gordon KX4Z
On Fri, Feb 28, 2025 at 4:48?PM Gordon Gibby KX4Z via <docvacuumtubes=[email protected]> wrote:
But I can’t figure out is how disconnecting a Lowpass filter would result in a lower voltage. It should result in a higher voltage. ?
I tried to look for what things might be shorting out. There’s a chance that the high-voltage system is shorting out but it’s only connected by 47 pf?
?and that’s not much. ?
Gordon?
On Feb 28, 2025, at 16:35, Evan Hand via <elhandjr=[email protected]> wrote:
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It should be possible to test the LPF selection process with a DMM.? Use USB, set the drive to 1 and the mic to 0.? Then, measure the voltages on the banded sections of the selection diodes.? Only one pair should be close to zero; the others should be close to the input voltage (12 volts) without the RF voltage doubler.
On Friday, February 28, 2025 at 12:53:23 PM PST, tomekdm sp7etd via groups.io <tomekdm@...> wrote:
If after de-soldering of C30 voltages on Q30 will be near voltages of Q10, so: E= 1.6, B= 2.4, C= 7.9 Then You need to replace C30 with any 100nF (0,1uF) ceramic capacitor.
If voltages will be still low as before: E= 0.0, B= 0.28, C= 11.00 Then Q30 needs replacement.
The RPi Zero 2 W has two USB 2.0 ports, I guess you could use an interposer board and include a USB-C connector, but it would only work at USB-2.0 speeds and increase the size of the radio.
Lev
HA3HZ
Richard AG5M
tomekdm sp7etd