Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
uBitx V4 Audio extremely quiet and other needed mods#ubitx
|
Our radio club just had several members purchase the uBitx, we intended to use it to learn about kit building and modifications over the next couple of months. So I am going to be assisting several people who have never built a kit before, some of whom have never used a soldering iron before, to make these kits. We all knew when we ordered them that there would be some modifications to be done, and we will have a fun time getting them working, but I think we need a little help.
I got my uBitx just about?two weeks ago. I got it wired up, got my nextion display connected, updated the firmware to the uBitx, all is well. I powered it up, and even at full volume I can barely hear it. Tried using headphones and a couple different speakers, this thing is just plain quiet.?So I helped one of the other guys wire his up on Saturday, and found the same problem. Both of our radios are extremely quiet.?Have I done something terribly wrong, or are these V4 boards really that quiet? Doesn't matter whether using headphones or a speaker, it is almost too quiet to hear. If I listen closely I can hear things, so I know it is tuning and receiving signals, but is extremely quiet.I can wire up an audio amplifier "daughter card", I have several Youda 10W audio amplifier ICs that can be used for this purpose. I want to make sure I didn't screw up first. And if the audio amplifier "daughter card" is necessary, where is the best place to connect it? Next, I have read a lot about spurious emissions and harmonics on this site and? ubitx.net, so I know that before they transmit, we need to check for spurious emissions, and more than likely will need to address that issue. I do have a spectrum analyzer to check them with, so that won't be too difficult, but which is the best fix for this issue? Since I am going to have to assist several people in my radio club to do the needed modifications I need a list of? mods that need to be done to these V4 boards. ?Is there a list that shows which mods are required on these boards that is in one place, or can?you guys help me to make this thread become that list? Thanks in advance, Erik Larson, AD7OV |
|
Erik
the radio may sound a little unusual since it is intentionally designed for good dynamic range.? you should be able to hear down to band noise.? do this experiment: unplug the antenna, the noise should go down -- especially true on the lower HF bands.? if the noise level drops when removing your antenna, it says the radio is fine.? there is plenty of audio using modern/cheap headphones.? please note with no AGC, one must manually adjust the volume control.? you may not hear band noise at the minimum setting of the volume control.? so try the experiment at mid range - as you go to higher bands you will need to turn up the volume control to hear band noise.? now band noise is a silly expression.? it is essentially the noise of the atmosphere plus whatever manmade noise you have on top of that.? okay the term works.? that nifty Milton speaker (if you have the Sunil case kit) does not have enough audio power in front of it to fill a room etc.? I would consider one of those commercial speaker amplifiers - they abound in the world economy (cheap might be very good here).? required mods for v4 board is quite a controversial topic!? first something is needed to reduce harmonic leakage around the low pass filters (either adding separate relays or hoping better relays will improve things enough).? second, added filtering at the 45 MHz IF.? if you have email address posted at qrz.com I will add a little info from our club build.? Curt WB8YYY |
|
Maybe there is problem with the sensitivity of your receiver. My unit drives a four inch speaker with plenty of volume.? Bill - K5MIL On Thu, Feb 7, 2019 at 8:52 AM <alphamale@...> wrote: Our radio club just had several members purchase the uBitx, we intended to use it to learn about kit building and modifications over the next couple of months. So I am going to be assisting several people who have never built a kit before, some of whom have never used a soldering iron before, to make these kits. We all knew when we ordered them that there would be some modifications to be done, and we will have a fun time getting them working, but I think we need a little help. |
|
Curt,
I'm not talking just band noise. Tuned to a station that is very strong on my Yaesu FT-991A (S9+ on the S?meter, I'd give a solid 5/9+ report). Removed antenna from FT-991A and connect to uBitx, set uBitx to same frequency, full volume into an 8 Ohm speaker, and into a cheap headset (also tried an expensive headset). The signal was so quiet that if everyone in the room was not silent, I could not hear it. Almost like I am feeding line level audio to the speaker with no amplifier in place. Turning the volume knob does adjust the level, I can make it even quieter, but at full volume on both radios that we tried, we barely get enough volume to hear. My email should be good on QRZ.com, but just in case, I do have ARRL forwarding on my call sign.. mycall @ arrl.net I would be happy to have any assistance you are willing to offer. We gutted some old dead Cobra 29LTD CB radios, and I designed and 3D printed a new face for them to hold the Nextion display and the tuning knob and volume knob (which were also 3D printed). So we have a bunch of parts from the original CB that can be scavenged, including it's Youda 10W audio amplifier IC, so I could wire that in, if I knew that was what was needed. Here is a pic of mine turned on to show off.. |
|
Bill,
I thought that too, which is why we wired up the second one to test. We are getting same results on both of them. Another club member has a V3 board, and his has plenty of audio. This made me suspect that the V4 board might have a problem in the audio chain, I understand that the V3 had an IC amp, and the V4 has a discrete amp. I haven't looked closely enough at the board to determine if that is the case, thought I'd see if others had seen the problem first. Erik - AD7OV |
|
This is unusual. Do you have access to a signal generator and or an oscilloscope? On Thu 7 Feb, 2019, 11:17 PM <alphamale@... wrote: Bill, |
¿ªÔÆÌåÓýVersion-4 uBitx boards require the addition of an outboard audio amp. They have very low audio output and the audio becomes distorted when pushed very hard at all. Most users attached the outboard audio amp to the whipper of the volume pot. You may wish to use RG-174 or other shielded cables to keep ground-loop oscillations and RF distortion in the AF chain to a minimum. I also added the Sotabeams SSB/CW audio filter in the chain prior to the outboard audio amp, which greatly improved off-frequency interference (Go to ). Its only $32.28¡well worth it! ? I also made the following update to the audio chain that helped improve sound level and quality¡ ______________________________________________ ? MOD POSTED ON JULY 16, 2018 Replacement to Q70 for more audio gain, less overload¡ Tom W1EAT? has noted that Q70, the audio pre-amp, has a really big job in the uBITX and sometimes gets overdriven by very strong signals.?? Tom also replaced the 2822 audio amp with an LM380 and lost around 8db in audio gain. So he though he would try another transistor to try and improve this situaiton. He had some 2SC945 transistors marked with the highest ¡°beta¡±(AKA hfe) rating, so I took one with a 360 hfe and replaced Q70.?? He made no other component changes. The 2SC945 is supposed to be specially designed for audio pre-amps, so it ought to be a good replacement. With RX voltage of 13.6, the Q70 collector voltage is 4.67 on the 2sc945. I should mention that I added a 16K resistor from the base to ground when Q70 was a 2n3904, which was suggested by W3JDR to reduce distortion. I did not remove that resistor. The results were totally positive. Tom has more AF gain, and none of the signals in tje IARU HF contest overloaded it. ______________________________________________ ? I hope this helps, ? David A Posthuma, WD8PUO 1 (616) 283-7703 ? From: [email protected] <[email protected]> On Behalf Of alphamale@... ? Bill, |
|
I'm suspicious of the step of going directly to the Nextion display and re-flashing the Raduino before checking out the board as it was shipped (i.e. aligned). In particular, if re-flashing means that the VFO and BFO settings are reset, the radio could be very quiet because the IF frequency is badly mis-aligned with the crystal filters.? I found that just entering the alignment menu resets both settings (ugh), forcing a complete re-alignment.? That's just plain annoying. That would make the radio pretty deaf, for sure. Hope that helps, -- Dave, N8SBES
|
|
My experience with the Nextion upgrade is that if you load a blank Arduino Nano with the firmware the calibration (and hence the sensitivity) of the rig can be impacted. If you upgraded the one provided it should not be an issue.?
The first thing that I found was that the BFO was off. This had a huge impact on the volume from the rig. Since you are using the KD8CEC firmware I would get the Memory Manager software to allow for easier changes in the calibrations.? I found a free audio spectrum analyzer software on the internet that I used with a usb mic. Should also work with the sound card in a laptop. I then started with the BFO set to 11997000 and tuned to some noise withou signal and sampled the audio. It should fall between 500 and 2700 hertz. It showed up clearly on my setup.? I then adjusted the BFO to center the response. This should center the receiver on the 12MHz crystal filter. I then did a zero beat against WWV to set the dial frequency. After doing this the signal level increased significantly.? Ultimatly I did add a cheap LM386 based audio amp. It solved the volume issue, however it created some feedback issues when at high volume levels and got extremely hot. The solution for that was to add a 7809 regulator and capacitors to drop the 12v+ (I was using a 13.5v supply) to 9 volts. Worked ok. ?Final solution was a 10w audio amp module. That was more expensive. If on a budget do not need to go to this level.? Most all of the v4 rigs that I know do have added audio amps. It can be connected as I did on the earphone jack so that it would drop the speaker audio when earphones are plugged into the jack. Those that do not use an auxiliary amp use earphones only.? 73 Evan AC9TU |
|
Dave,
I did wonder if there might be something lost in the upgrade, but reading up on it looked like it would retain whatever factory settings had been saved to EEProm, so I went ahead and did it. Evan, It was upgraded from the provided nano on the raduino. I did not run it with the stock firmware before upgrading, however, so I can't say if the upgrade to the CEC firmware could have caused this issue. Your procedure for alignment is straightforward, can't hurt anything, if anything it will improve by recalibration, so I will attempt as you outlined first when I get home tonight. I will reply back here with results. Erik, AD7OV |
|
Evan,
I tried re-aligning the BFO as you said. When I first read it with memory manager, it had values that were WAY away from the starting point you suggested (BFO was 14950000). It did appear to help with the weak audio. Scope shows good audio response from 500 to 2500. Transmitting from a 5W transmitter across the room, I am now able to receive a signal that is capable of driving the speaker I have. I don't know if I have it tuned perfectly, but I think this is on the right track. This weekend when I have more time to work on it, I will hook it up to the service monitor and put a solid 1K audio tone in on a few different frequencies and fine tune it.? Thanks for pointing me in the right direction. Erik - AD7OV? |
|
Ok, so we got the rig on a service monitor this weekend.. After using the service monitor to align the radio (the procedure used from the hfsignals website did get it close, and the one suggested by Evan got even closer) I was able to inject a signal at 29.7 MHz and at 1.0 MHz and using a audio spectrum analyzer on the output from the ubitx I was able to fine tune the alignment so that a 1KHz test tone put into the injected signal came out of the ubitx as a 1KHz tone, at the exact dial frequency of the signal. Evan's alignment procedure did get me within about 500 on the number needed for the BFO setting to accomplish this, so thanks for that Evan.
Here is what I found on the service monitor: With a signal input of -45 dbm, the ubitx has plenty of audio, and can actually overdrive the audio amplifier chain if turned up too much. -45 dbm is equivalent of 30db over S9, or S9+30 signal. This is close to what we get from the AM radio station that is only about 4 miles away, volume from the test signal and the radio station are about the same at this level. With a signal input of -70 dbm the ubitx made enough audio with the volume turned clear up that we could hear the test tone, but it was quiet. -70 dbm should be an S9 signal of 50 uV, so I would have expected much louder signal. It was, however a very clear signal. With an input of -100dbm (around S4 on the scale, or 1.6 uV) the signal was present, but barely audible to our ears. With an input of -120 dbm (0.2uV or S1 on the scale) we could not hear the signal out of the speaker, however the spectrum analyzer could still detect it's presence. My Conclusion: The ubitx has a very sensitive receiver, and it works very well even at the lower signal input levels, but the amount of amplification in the AF stage is inadequate if the signal is below about S7 in strength. We tested on four different V4 ubitx boards that were built within the last week, and got the same results on three of the four. The fourth one was just a little louder than the other three, not much, but enough we could tell a difference. Ashhar, hopefully this extra information is helpful to you. Do my boards appear to be operating properly, in which case we may just need to add an audio amplifier and AGC circuit to make them easier to use, or does it look like these are not functioning as designed? Do these results look similar to what others are seeing with this board? For what it is worth, the V3 board one of our guys has is about 2 to 3 times louder than any of the V4 boards. I am not opposed to adding an audio amplifier if that is the correct solution to the perceived problem with the audio, but I would like to know that it is the best course of action before I proceed. I dislike fixing problems with a tourniquet when a bandage would have sufficed, if you know what I mean. Thank you everyone for the kind assistance you have offered here. Erik Larson - AD7OV |
|
Erik
you can imagine your 4 rigs there, and your nice data gathering, describe the audio output.? I find audio is adequate in headphones - using speakers perhaps greater difference of opinion may abound.? please note that v4 uses a simple pair of transistors for the audio output, perhaps with less max power output than the previous (and upcoming) versions that use an IC.? I confess for CW work I need audio filtering anyway, so I use a NESCAF - that works nicely for SSB also -- this includes a LM386 output stage to drive my headphones.? I guess the speaker isn't finding much use in my operating.? BTW I installed the sidetone mod described at the K3PZN website.? This one is configured to route such that it isn't impacted by the volume setting.? its a cut trace, a 1meg resistor in my case and a piece of wire.? If your builders want more robust audio inside the box - I am suspicious a search here will provide some ideas.? Also check ubitx.net to see what is posted, but I find content isn't any better vetted than what is here.? 73 Curt |
|
The v4 audio amp was meant for comfortable headphones listening. You can add an LM386 amplifier or even a TDA2003 in place of this for more gain. Without the agc, it is best to add the gain after the volume control - f On Mon 11 Feb, 2019, 7:29 AM Curt via Groups.Io <wb8yyy=[email protected] wrote: Erik |
¿ªÔÆÌåÓýFWWI have a v3 and somehow using wspr I managed to damage U1 which is a TDA2822M audio amp. The output is now very low. The TDA is a stereo amp and the other channel is unused so I may use that. In the meantime, I have wired in a nice little 386 amp on a
small board that is available from marlin p Jones item number 31805 m1 for $3.95. It works great and has plenty of output
73
|
|
Thanks Ashhar for confirming that the audio amp is what is needed if we are going to use a speaker. I agree that now the volume is adequate using a set of headphones. My original problem was solved by properly aligning the receiver.
I was comparing to a V3 board that one of the other members already had and it's greater output of audio made me wonder if we had done something wrong in building this one. I did not realize that the v4 was designed to have lower audio output than the v3 board. I had assumed that the discrete amp had been designed to replace the IC within the same specs. Thanks to everyone here for the help and the ideas. This is a wonderful little radio for experimenting with, and we now know exactly what to expect as we build them in our group. Erik Larson - AD7OV |
|
The v4 I have is in the "official" enclosure kit, which comes with a speaker.? I've normally used only the speaker, as I don't have the AGC mod installed, and I'm not eager to suffer any (more) hearing damage from using headphones with a non-AGC-protected receiver. In any event, the speaker seemed to put out plenty of audio.? I don't think I ever had any issues with that. On the other hand, after I put the v4 on my spectrum analyzer and found out how dirty the transmitter was, I pulled it off the air, and have been waiting for all the hubbub to settle down over how to mitigate those issues. Seems now the best (easiest?) path forward is to order a v5 board and replace the v4 with the v5.? That said, I ordered a v5 a few days ago, but have yet to receive a DHL tracking number.? I may have missed the initial order of 100 units, and may now be waiting for a while. That's OK by me.? I have plenty of other radios (K3S, IC-7000, FT-817, KX2, QCX40) to play with in the meantime, so when it comes, it comes. I did alert my local radio club about the release of the v5, and urged those that haven't finished their v4 build to consider upgrading.? We had put together a quantity buy of the v4 boards, but as far as I know, only two or three of us had actually gotten their boards installed in an enclosure and on the air. 73, -- Dave, N8SBE
|
David Posthuma
to navigate to use esc to dismiss