bitx40 original wireup directions
I am looking for the original wire up instructions for the $59 bitx40 kit - I had an issue with mine part way through upgrading, and have gone back to start up (reflashed the arduino sketch) and need the original wiring instructions which I can no longer find on the hfsigs site. Then I will start to modify again!
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Re: 3D printed folding sBITX tilt legs
#sBitx
Gerry
? I can print one for you if you would like. The biggest expense might be shipping. I'm in NE Ohio.
? BTW - big box hardware stores like Lowe's and Menards carry the screws. The 12mm M4 screws are $1.29 for a three pack at Menards.
? BTW2 - many public libraries have printers for use for the cost of the filament. There are also many Maker Spaces around that have printers.
Mike
?? Glad you found it useful.
--
73
??? Bob? KD8CGH
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Re: ubitx audio amp problem discovered
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Re: ubitx audio amp problem discovered
Doc, in the linked vid at 11:10, it makes sense that the output impedance is about 5 Ohms. Then, after a jump edit, he multiplies it by 10 and uses 50 Ohms to solve for the output cap. Where did the 10 come from? It was an easy to follow vid until that Deus ex machina moment.?
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On Mon, Jan 22, 2024 at 05:34 PM, Gordon Gibby wrote:
Probably, Raj.? Ultimately I'm trying to understand how to implement Farhan's mod.?
Since I don't yet know how to create the emitter follower he described, I'll go back to applying fiberglass to the bottom of my boat.?
Thanks, Andy
On Mon, Jan 22, 2024 at 12:22 AM, Raj vu2zap wrote:
Andy,
You are talking about a hard to get audio transformer!
Raj
On 22/01/2024 8:21 AM, AndyH wrote:
Could this be fixed with a 9T:2T transformer between C63 and the mixer pad, and rebiasing Q6 for a gain of 2-3?
And/or, could someone flesh out the emitter follower and specify which parts from the emitter of Q6 should be removed? (Just C62 and R64?)
? ?Thanks!
? ? ?73, Andy, KG5RKP/MM
On Sat, Jul 15, 2023 at 09:18 PM, Ashhar Farhan wrote:
Thanks for the analysis. There are two other significanr issues with the current mic amplifier.
1. The output impedance is 1000 ohms, the modulator needs a 50 ohms drive.
2. The gain is not less but too much. The electrer mic produces about 50mV of audio, the modulatoe needs less than 150mv drive. A gain of two or three is more than sufficient. The apparent loss is due to the mismatch between the 1000 ohm output and the needed 50 ohms drive.
These can be solved by adding an emitter follower with a 47 ohms resistor in series with the output of the emitter follower and removing the emitter bypass of the original mic amplifier.
- f
I've been working on the uBitx audio circuit for a while now and I think I've discovered a problem that I've never seen anyone mention before. If anyone has experience with this circuit, please review and let me know if I've missed anything. Here are my notes:
?
?Audio Amp notes.
?
The uBitx has always had challenges with the audio amp. It has insufficient gain for the condenser mic that is provided. Solutions include:
?
a. Use a mic with an amplifier built in.
b. Add an additional amplification stage such as the SSM2167.
c. Increase the mic circuit gain.
?
Mic amplifier circuit with suggested modifications. Also showing the load of the following stage.
?
SEE ATTACHED FILE
?
Analysis:
Given that the receive transistor Q70 is connected directly to the output of the microphone amplifier, the output of the mic amp must be less than 0.6v. We¡¯ll say 550 mV to give us a bit of safety margin.
The input drive required to achieve 550mV out of the mic amp is 200mV. Most have claimed that the mic amp has a gain of around 20 due to the collector resistance of 1k divided by the emitter resistance of 47 ohms. This simple analysis is incorrect because it neglects the load impedance of the mixer circuit. Spice analysis and actual observation shows the actual gain to be about 2x or 3x.
A big problem with this mic amplifier is that it is incorrectly biased. With the originally specified bias resistor R61 set at 2.2k, the transistor runs out of emitter current at about 160mV of output voltage. In addition to limiting output, this causes distortion of the audio waveform. By increasing R61 to 10k, the circuit can easily output the 550 mV (1.1V P-P) originally suggested.
In my own uBitx, I have chosen to use the SSM2167 as a preamp in order to enjoy some voice compression. However, the simplest solution is to decrease R63 to 10 to 22 ohms. I¡¯d advise not to go lower than 10 ohms, since that circuit should fully drive the mixer with a mic output of only 40 mV. But before doing anything else, increase R61 to 10K.
?
?
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Re: ubitx audio amp problem discovered
Thanks Doc - I hadn't seen that lecturer yet. Based on the first couple of minutes, I'll subscribe and watch.
? ?I'm not an EE and don't have a career's worth of tribal knowledge to fall back on. At 61 I don't feel much more anchored in this than when I was 14 and trying to apply my crystal radio knowledge to a multi-band SSB receiver project from an ARRL handbook. LOL
I can work through the math for a single transistor amplifier and adjust gain. (Primarily thanks to Farhan's feedback amp vid, and Charlie Morris' ZL2ZTM tutorials.)? I don't have any idea what happens to that amp when I glue on another BJT. (Is it added like a stage with a cap separating them, or like the way Q12 is added to Q11?) I've already fallen flat with the "Audio isn't RF so no, not gonna get through this by winding a toroid!" Glitch. Ha!
? ?I also wasn't clear on exactly which of the feedback parts Farhan suggested should be removed from the existing amp. I understand that R63, C62, and R64, all on the emitter of Q6 are 'feedback', and I think I understand that the paralleled C62 and R64 are probably the AC feedback parts.? Should both be removed, or one, or?
? ?Anyway...thanks again.? 73, Andy
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On Mon, Jan 22, 2024 at 05:34 PM, Gordon Gibby wrote:
Probably, Raj.? Ultimately I'm trying to understand how to implement Farhan's mod.?
Since I don't yet know how to create the emitter follower he described, I'll go back to applying fiberglass to the bottom of my boat.?
Thanks, Andy
On Mon, Jan 22, 2024 at 12:22 AM, Raj vu2zap wrote:
Andy,
You are talking about a hard to get audio transformer!
Raj
On 22/01/2024 8:21 AM, AndyH wrote:
Could this be fixed with a 9T:2T transformer between C63 and the mixer pad, and rebiasing Q6 for a gain of 2-3?
And/or, could someone flesh out the emitter follower and specify which parts from the emitter of Q6 should be removed? (Just C62 and R64?)
? ?Thanks!
? ? ?73, Andy, KG5RKP/MM
On Sat, Jul 15, 2023 at 09:18 PM, Ashhar Farhan wrote:
Thanks for the analysis. There are two other significanr issues with the current mic amplifier.
1. The output impedance is 1000 ohms, the modulator needs a 50 ohms drive.
2. The gain is not less but too much. The electrer mic produces about 50mV of audio, the modulatoe needs less than 150mv drive. A gain of two or three is more than sufficient. The apparent loss is due to the mismatch between the 1000 ohm output and the needed 50 ohms drive.
These can be solved by adding an emitter follower with a 47 ohms resistor in series with the output of the emitter follower and removing the emitter bypass of the original mic amplifier.
- f
I've been working on the uBitx audio circuit for a while now and I think I've discovered a problem that I've never seen anyone mention before. If anyone has experience with this circuit, please review and let me know if I've missed anything. Here are my notes:
?
?Audio Amp notes.
?
The uBitx has always had challenges with the audio amp. It has insufficient gain for the condenser mic that is provided. Solutions include:
?
a. Use a mic with an amplifier built in.
b. Add an additional amplification stage such as the SSM2167.
c. Increase the mic circuit gain.
?
Mic amplifier circuit with suggested modifications. Also showing the load of the following stage.
?
SEE ATTACHED FILE
?
Analysis:
Given that the receive transistor Q70 is connected directly to the output of the microphone amplifier, the output of the mic amp must be less than 0.6v. We¡¯ll say 550 mV to give us a bit of safety margin.
The input drive required to achieve 550mV out of the mic amp is 200mV. Most have claimed that the mic amp has a gain of around 20 due to the collector resistance of 1k divided by the emitter resistance of 47 ohms. This simple analysis is incorrect because it neglects the load impedance of the mixer circuit. Spice analysis and actual observation shows the actual gain to be about 2x or 3x.
A big problem with this mic amplifier is that it is incorrectly biased. With the originally specified bias resistor R61 set at 2.2k, the transistor runs out of emitter current at about 160mV of output voltage. In addition to limiting output, this causes distortion of the audio waveform. By increasing R61 to 10k, the circuit can easily output the 550 mV (1.1V P-P) originally suggested.
In my own uBitx, I have chosen to use the SSM2167 as a preamp in order to enjoy some voice compression. However, the simplest solution is to decrease R63 to 10 to 22 ohms. I¡¯d advise not to go lower than 10 ohms, since that circuit should fully drive the mixer with a mic output of only 40 mV. But before doing anything else, increase R61 to 10K.
?
?
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Re: 3D printed folding sBITX tilt legs
#sBitx
I don't have access to a 3d printer.? I would be willing to
reimburse somebody to make me one of these folding supports.? I
would like the person to include the screws - a local hardware
supplier has them, but $25.00 minimum order for 5 screws!!!!
Thanks
Gerry Sherman
Sent by the Windows 11 Thunderbird
On 2024-01-23 17:24, Mike - KD4MM
wrote:
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Thanks Bob!? I have been using any number of things to tilt my
sBitx and should have thought of this.? I fired up a 3D printer
after lunch and voila!? Fits like a glove and just what I needed.
73, Mike
KD4MM
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Re: Sbitx vs ubitx power levels
Hi Roy,
Do you have a link that I can look at that you recommend for making one of those? What bands are you able to use it on without a tuner?
73, Scotty
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Re: 3D printed folding sBITX tilt legs
#sBitx
Thanks Bob!? I have been using any number of things to tilt my sBitx and should have thought of this.? I fired up a 3D printer after lunch and voila!? Fits like a glove and just what I needed. 73, Mike KD4MM 
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Re: Sbitx vs ubitx power levels
I¡¯ve had good luck with a 40m EFHW and 49:1 transformer. ?It is about 26-ish feet long, don¡¯t revenge actual trimmed/tuned length. ?
73 Roy
On Tue, Jan 23, 2024 at 16:18, Scotty R via groups.io < Theroadcalls1@...> wrote: Hi Evan,
I really do appreciate the advice and reasons that you have stated. Since I really like rtty/bpsk style modes as well as cw, I will most likely go for the sbitx model. Also, if modification is needed to bring the ubitx up to what I want, then I am best to start out with the sbitx. I do enjoy ssb from time to time too though. When on a limited radio equipment budget, planning is needed. Not sure of the portable antenna yet, but it will most likely be no larger than a 20 meter inverted vee so that it will fit in a camp site with our pull behind camper at state parks. I might try making it multiband with a tuner and twin lead cable.
Many thanks, 73
Scotty
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Re: Sbitx vs ubitx power levels
Hi Evan,
I really do appreciate the advice and reasons that you have stated. Since I really like rtty/bpsk style modes as well as cw, I will most likely go for the sbitx model. Also, if modification is needed to bring the ubitx up to what I want, then I am best to start out with the sbitx. I do enjoy ssb from time to time too though. When on a limited radio equipment budget, planning is needed. Not sure of the portable antenna yet, but it will most likely be no larger than a 20 meter inverted vee so that it will fit in a camp site with our pull behind camper at state parks. I might try making it multiband with a tuner and twin lead cable.
Many thanks, 73
Scotty
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Re: Sbitx vs ubitx power levels
Hi Scotty,
I own six uBitx and two sbitx.? The uBitx, as delivered, can do SSB, and with a PC and sound card, it can do digital modes.? It is marginal for CW as it does not have a narrow audio filter.? The significant advantage is the lower cost.? It also has a lower learning curve to modify the software that controls the radio.? It is a mature design, as few new mods have been posted recently.? Older mods are becoming unavailable.
The sbitx is good at CW, SSB, and can do digital modes with the internal Raspberry Pi.? It has a steeper software learning curve as it is a software-defined radio.? It is early in the maturity cycle, as updates are almost monthly and are free.? It will get even better and should cost nothing for the improvements.
The actual cost difference will depend on how you want to use it.? As a portable SSB rig, the uBitx wins on cost.? As a digital rig, the sbitx wins.? I recommend the sbitx, as the functionality improvements are just starting, and most are free software based features.? You will be purchasing or building hardware to add functions to the uBitx.? I am in the process of adding functionality to a uBitx to make it CW-worthy, as well as adding AGC, S-Meter, and taming the power curve vs frequency.? The parts cost $100 unless you have an extensive parts/junk bin.
I recommend the sbitx.
My opinion, others may differ, and YMMV
73
Evan
AC9TU
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Re: 3D printed folding sBITX tilt legs
#sBitx
Mark
? Yes, those are the dimensions I used for the back of the tilt mount. They are explicitly declared in the OpenSCAD source file.
? As mentioned, I also checked the others in the drawing by printing a thin template and laying it on the back of the sBITX to check hole alignment.
--
73
??? Bob? KD8CGH
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FWIW I have kept track of storage performance I measure using linux's 'hdparam' which is a read-only test.? I have a little piece of shell code that does 10 runs and reports the min/max/avg read throughput. Below is the summary of the data, updated last night after testing the Pi 5 PCIe NVMe setup.  As usual, your mileage may vary, but I gotta say, the Pi 5 with Gen3 PCIe feels wikked fast! Personally, I hope future Pi devices provide more than one lane of PCIe to external devices. We see the 'workstation' got almost 3x better performance, and I bet it's due to more PCIe lanes. -- Regards, Dave, N1AI
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On Tue, Jan 23, 2024 at 12:58 PM, WB6GJE Mike wrote:
Get a consensus of advice and go with information that appears consistently across a number of YouTube videos and/or blog posts.
Wow, that's a perfect lead-in for me.? I wrote most of the below for another platform, but IMO it fits into this discussion here about Pi 5 and NVMe.? It also fits into some stuff I wrote earlier about how I feel Pi will be under more pressure from small form-factor (SFF) PCs using x86 processors, and that the sBITX community will have to be ready for things to change more rapidly than in the past
IMO design decisions made by the Pi Foundation make it relatively easy for them to move on to Pi 6 and beyond because they've put all the IO onto a separate chip.? That makes it easier for them to drop a newer/faster CPU into their design than they have in the past, and such newer/faster ARM CPUs already exist.? ? They may have to, because SFF PCs IMO are already strong competitors so there is already a competitive threat that could easily intensify.? I'm saying this since I think a lot of people have gotten used to the slower development pace of the COVID era, but I think those days are long over.??
So, we see that Jeff Geerling is jumping onto the Pi 5 vs N100 SFF PC bandwagon after Christopher Barnatt / Explaining Computers did so a week or so ago.??
Jeff:??
Chris:??
Jeff is doing an almost exact match on price and is fairly close on form factor, whereas Chris's N100 PC was not a SFF PC, it was a mini-ITX so bigger case and PSU and cost 1.5 times more than his Pi 5 setup.? ?Yet Chris's N100 has very similar specifications to Jeff's.? Chris provides more details on specifications and performance than Jeff did.? For instance Chris tells us his motherboard supports two-lane PCIe V3, whereas Jeff doesn't get into that level of detail.
Jeff's video is really amusing to me since my PCIe to NVMe adapter arrived last night for my Pi 5 and I was doing almost all the same stuff he was doing in the setup phase of this video myself last night.? My Pi 5 setup is pretty much identical to Chris's.? We both have the Pineberry Pi Hat! Bottom whereas Jeff has the Top model.??
Jeff is right that the Pi world requires you to select, purchase and assemble more 'stuff' to get a useful setup whereas most SFF PCs come with all the stuff you need right out of the box.? ?He is also right that it's really hard to know if a given Pi case will work with a given top/bottom device and still provide good air flow, still have the holes line up with the jacks, still be able to get at the sdcard, power button, camera/display connectors, etc.
My summary of both videos is that at a similar price point the N100 platforms delivers somewhat faster performance but draws somewhat more power both at idle and under load to deliver that performance.? The N100 is clearly faster at anything that involves graphics and video since it has a better GPU with better software support.? The N100 takes up more space, but is more expandable.? Jeff's N100 has room for a 2nd NVMe storage device and has a slot for mobile data dongles too.? He doesn't say if the memory is expandable or not.? Also, I don't know how 'battery friendly' its voltage requirements are.
On the software side assuming you are using the "native" software for the box, Debian Linux on the Pi boots up pretty much ready to use whereas Windows makes you accept a EULA, accept or avoid a Microsoft account, turn off a whole bunch of data collectors, only provides the Edge browser by default etc so is worse from a privacy point of view.? Windows is also a bigger target for malware providers although one shouldn't presume Linux isn't also targeted quite often too.? And, of course, you can always install Debian on the N100 PCs and bypass Windows entirely.? Regardless of what thinks of Windows, though, being able to offer it is a competitive advantage, IMO.
--
Regards,
Dave, N1AI
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Thanks for all the answers!
: )
73,
Rafael
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On 1/19/24 14:42, Evan Hand wrote: On a search, I found that Zeners most often fail shorted rather than open on over current.? Since D3 is for protection, failing shorted would protect the devices taking power from the 5-volt rail from a voltage above the Zener voltage.? It would put a significant load on the regulator supplying the 5volts.? If D3 fails, I would suggest verifying the 5volt buck converter is working correctly, as that is what would most likely have had to supply the overvoltage to cause D3 to fail.
The 1/2-watt Zener should work as a sacrificial part on buck converter failure, provided a current limiting device is upstream of the regulator, like a fuse on the supply input.
73
Evan
AC9TU
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Re: Rafael's 64-bit image
Hi Hank,
Can you be a bit more specific? There is no i2s-nmap, but i2s-mmap.
- Rafael
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On 1/21/24 00:31, Hank Beisheim via groups.io wrote: Rafael,
I'm getting an error on boot. Can not load overlay i2s-nmap. This is from your image.
A search turns up nothing. What's missing?
--
Hank W6IR
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Re: Sbitx vs ubitx power levels
Thank you for the reply. I have been doing some research into these radios for a possible purchase. I am leaning toward the sbitx at the present.? As a past Radio Shack repair tech, I am very familiar with service of electronics. If I do purchase one of these, I am hoping repair will never be needed. But the fact that the schematics are available and a very straightforward design make them very appealing, compared to many other radios I have found. They seem to be very easily modifiable for any new things I might wish to add. My biggest challenge will be to learn the coding to modify software to implement any modifications! If I get one, I will want to make a battery pack and perhaps an antenna tuner for camping or even while sitting in the front yard supervising grandchildren. It seems a better choice than playing games on a cell phone.
Scotty
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Re: Sbitx vs ubitx power levels
Topographically they are very similar.?
Its small design differences.
Things like lower output load resistance output transformer turns ratio,
construction,?and increased Drive to meet the need.
Heat sinking is also critical, as are things like lead lengths and mechanical layout
are also factors.
I've seen uBitx deliver over 15W when the drivers were up to the task.
--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
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Re: 3D printed folding sBITX tilt legs
#sBitx
If you use Fusion 360, you can upload and scale a photo to be used as the template for your base sketch. ?With very little practice you can get parts to be exact on the first or second try.?
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Re: 3D printed folding sBITX tilt legs
#sBitx
Bob,
I think I got it. Imported your backbrace stl into tinkercad and used the grid there to get it to the mm.
Left to right is 196mm and the "middle" hole is 42mm from left.??
Let me know if you come up with something else.
73
Mark
--
AJ6CU/7
KD8CEC 2.0, Nextion Screens,? and open source uBITX Raduino boards for Arduino IOT, BLE, RP2040, Teensy 4.0, and Raspberry Pi Pico
https://github.com/aj6cu
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Matt KA2TVX
Bob Benedict, KD8CGH
Scotty R
Dave, N1AI