Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
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
-------- Original Message --------
Subject: Re: [BITX20] uBitx V4 Audio extremely quiet and other needed
mods#ubitx
From: "David Posthuma" < davep@...>
Date: Thu, February 07, 2019 1:17 pm
To: < [email protected]>
Version-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 ? ? 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
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Re: ubitx mobile in a car
I've been trying to get my BITX40 working in my van, but have run
into two problems - the worst being ignition noise (spark plug
popping) and the second being the antenna isn't that efficient -
it's a homemade center-loaded bug-catcher with a homemade tuner
(Pi design) to get the SWR down to reasonable levels (below 1.5 to
1).? I'd rather have had a T-tuner, but the variable caps I have
are the wrong type - it would likely be far more efficient for
this purpose.
My reason for choosing 40 instead of running the BITX20 (V3) I
have is primarily because I hear little activity on 20 beyond nets
and contests, plus I like to chat with people - I'm not interested
in trying to make as many contacts as I can.? 40m is perfect for
me because it's more local and there are more rag-chewing
sessions.? (The only drawback to that is many of the political and
religious views I hear drive me away, plus so many run huge
amounts of power and it's hard to get through that.)
As far as operating mobile, not having a good noise blanker is a
problem.? I thought it was coming in through the antenna, but
after much experimentation, realize that it's somehow being
brought in through the DC line - and somehow coupling to the
antenna circuit when the antenna is connected (it's not a ground
loop - eliminated that possibility).? I can, by using a huge
enough choke (thick steel ring with many turns of heavy wire),
reduce the noise significantly, but I can't eliminate it and it's
still too much to listen to.? Back to the drawing board!
The BITX radios would be perfect for mobile use, if we could get
around some of these difficulties!!!
My two cents worth...
Bob
On 2/7/19 9:42 AM, Ted via Groups.Io
wrote:
toggle quoted message
Show quoted text
I've moved
the automatic tuner originally purchased for the car to the tiny
back yard random-wire farm for now, and tentatively plan on
tuning my vehicular antenna to 40 alone. 20 would be more
logical, though, on a few fronts. If the spectral purity of the
incoming V5 runs thru my amp without going nuts as the V4 did,
then that will influence the final direction to a degree if only
to give me choices (QRP or enhanced-flamethrower mode).? There's
always the Armstrong multi-band tuning method (hand-switching
taps).? My rear hatch is bonded to the frame (twice), the tuner
was bonded to the chassis, and the remote head I was using was
fully shielded, this and that bonded, the whole mess. Prior work
putting radios in cop cars and fire trucks provided some
valuable lessons in RF-leak suppression and containment along
with playing with Heathkit SB-101 mobileering decades ago with a
2.5" coil and full 8' steel whip on a ball mount (that looked
scary but worked great).
Not nearly so
long ago (8 or 9), I had an MFJ-9420 SSB/CW rig that sounded
beautiful with its built-in compression and
temperature-sensitive, analog tuning. That fed a home-made,
shunt-fed base-loaded whip built upon an industrial-grade NMO
base that was mounted upon an angled clamp-mount to the hatch of
a former vehicle of the day.? For what it was, outstanding
reports were enjoyed - so, there is the chance of simply
invoking the use of that antenna again and using that as a base
line for possible future work.? By the way, that antenna base
was from a 5/8-wave VHF antenna whose load coil was stripped
out, then epoxied within a 1.5" I.D. plastic tube. I forget how
many windings or what length, but it went the approximate one
foot of length up that tube and then to the original S/S whip at
the top. In fact, the original VHF load's top hat with set screw
were epoxied into the top of the tube, to hold the whip. The
windings were connected to the shell of the NMO base part and
also to the top hat & whip.? Experimental means allowed me
to find a point for the base center (the part with the RF),
coming out of an access hole in the pipe, to connect in shunt
form to the windings. A near-perfect match having been found,
the shunt was soldered in place and the whole affair
weatherproofed.?? Again, signal reports were well appreciated on
this arrangement;? The move to the current trials are for want
of multiple-band operation for? EMCOMM use and/or digital
modes.? Maybe that's too much to expect with this setup and I'm
thinking of allowing the other uBitx project in the works to
fill that purpose, and set up the current project as a mono band
mobile with the earlier, proved antenna. We will see.
Watch out for
us "cagers" while out riding.? Some of us try to do our part.
-Ted
K3RTA
Newark, DE?
USA
|
Re: ubitx v5 is in production
Curt, 10 mhz and 18 mhz ar3me not compliant on ssb. This is alright for 10 mhz, as it has no ssb permit (unless you are running digital modes). - f
Yes mr. RC.... I see same thing as you !? Clearly not compliant on 30m.? To my surprise this seems to be a mixer related spur, not a harmonic.? I was skeptical about Axicom relays having sufficient isolation - but this data set conveys they do on this unit - nice so far.?
Both CW and SSB paths need to be tested as they are different transmit chains.? (But on CW it does not use mixers - so primary spurs are harmonic, PLL, or leakage related).?
Being off a fraction of a dB on 28 MHz, well, then we start to question accuracy of measurement.? Possibly the 28 MHz antenna might supply the extra fraction of a dB rejection.?
These remaining spurs would seem to relate to the added 45 MHz filtering and change to shunt inductors on the crystal filter.?
If one's country does not have the 30m allocation (I don't know if India does?) - I could see some declaration of victory.? But maybe we should retain a little skepticism on 100% of v5 boards passing for spurious compliance in all bands.? Honestly this looks better than I expected (sample of 1) for implementing the v5 changes.?
Curt
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Re: ubitx v5 is in production
Yes mr. RC.... I see same thing as you !? Clearly not compliant on 30m.? To my surprise this seems to be a mixer related spur, not a harmonic.? I was skeptical about Axicom relays having sufficient isolation - but this data set conveys they do on this unit - nice so far.?
Both CW and SSB paths need to be tested as they are different transmit chains.? (But on CW it does not use mixers - so primary spurs are harmonic, PLL, or leakage related).?
Being off a fraction of a dB on 28 MHz, well, then we start to question accuracy of measurement.? Possibly the 28 MHz antenna might supply the extra fraction of a dB rejection.?
These remaining spurs would seem to relate to the added 45 MHz filtering and change to shunt inductors on the crystal filter.?
If one's country does not have the 30m allocation (I don't know if India does?) - I could see some declaration of victory.? But maybe we should retain a little skepticism on 100% of v5 boards passing for spurious compliance in all bands.? Honestly this looks better than I expected (sample of 1) for implementing the v5 changes.?
Curt
|
Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
Version-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 ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of alphamale@...
Sent: Thursday, February 07, 2019 12:47 PM
To: [email protected]
Subject: Re: [BITX20] uBitx V4 Audio extremely quiet and other needed mods#ubitx ? 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
|
Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
Ashar,
Yes, I have access to both a signal generator and an oscilloscope.?I am at work right now, though. It will be 7 hours from now before I can test things, but if you will give me a procedure to follow, I will do it and post results here when done.
Erik - AD7OV
|
Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
This is unusual. Do you have access to a signal generator and or an oscilloscope?
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
|
Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
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
|
Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
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..
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Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
Maybe there is problem with the sensitivity of your receiver. My unit drives a four inch speaker with plenty of volume.?
Bill - K5MIL
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? , 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
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Re: Help with no SSB TX
#ssb
Hi Evan,
clock 1 seems to be about 33 Mhz and clock 2 about 50.49 ? ? I'm using high impedance probes
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Re: uBitx V4 Audio extremely quiet and other needed mods#ubitx
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
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Same value as in the kit (10k). Make sure it is an audio taper pot.
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Ross, The stock pot is 10k.? For volume you want logarithmic not linear.? Here is one several of us have used with success? Another suggestion, if you view the list at /g/BITX20/topics instead of individual emails there is a search available.? It is far from perfect. --
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I intend to ?replace the volume control pot so a real knob can be used, when does the group suggest for the ohm value of the potentiometer. ?Cheers Ross?
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Re: Help with no SSB TX
#ssb
Here's a pic of that area! :)
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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
|
Cheers ?for that Ted, I will have to give much thought to your suggestions. ?The learning novice I am is still very much the "tab A into tab B type of guy. Ross?
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Re: ubitx v5 is in production
I've been looking at Farhan's v5 Spectrum Captures.? Maybe my old eyes aren't seeing things correctly, but it looks to me like the v5 is non-compliant per US FCC regs at 10MHz (-63 db - (-24.73 db) = -38.27 db), and borderline at 28MHz (-63 db - (-20.13 db) = -42.87 db).? FCC requirement is -43 db.
So the v5 uBITX looks much better than the prior versions, but I'm not sure we're 100% there yet.
Can someone else look at those photos and see if I'm just not reading things right?? I wear trifocals, and even on a 26" monitor some of those numbers are rather tiny for me... :(
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Re: ubitx mobile in a car
I've moved the automatic tuner originally purchased for the car to the tiny back yard random-wire farm for now, and tentatively plan on tuning my vehicular antenna to 40 alone. 20 would be more logical, though, on a few fronts. If the spectral purity of the incoming V5 runs thru my amp without going nuts as the V4 did, then that will influence the final direction to a degree if only to give me choices (QRP or enhanced-flamethrower mode).? There's always the Armstrong multi-band tuning method (hand-switching taps).? My rear hatch is bonded to the frame (twice), the tuner was bonded to the chassis, and the remote head I was using was fully shielded, this and that bonded, the whole mess. Prior work putting radios in cop cars and fire trucks provided some valuable lessons in RF-leak suppression and containment along with playing with Heathkit SB-101 mobileering decades ago with a 2.5" coil and full 8' steel whip on a ball mount (that looked scary but worked great).
Not nearly so long ago (8 or 9), I had an MFJ-9420 SSB/CW rig that sounded beautiful with its built-in compression and temperature-sensitive, analog tuning. That fed a home-made, shunt-fed base-loaded whip built upon an industrial-grade NMO base that was mounted upon an angled clamp-mount to the hatch of a former vehicle of the day.? For what it was, outstanding reports were enjoyed - so, there is the chance of simply invoking the use of that antenna again and using that as a base line for possible future work.? By the way, that antenna base was from a 5/8-wave VHF antenna whose load coil was stripped out, then epoxied within a 1.5" I.D. plastic tube. I forget how many windings or what length, but it went the approximate one foot of length up that tube and then to the original S/S whip at the top. In fact, the original VHF load's top hat with set screw were epoxied into the top of the tube, to hold the whip. The windings were connected to the shell of the NMO base part and also to the top hat & whip.? Experimental means allowed me to find a point for the base center (the part with the RF), coming out of an access hole in the pipe, to connect in shunt form to the windings. A near-perfect match having been found, the shunt was soldered in place and the whole affair weatherproofed.?? Again, signal reports were well appreciated on this arrangement;? The move to the current trials are for want of multiple-band operation for? EMCOMM use and/or digital modes.? Maybe that's too much to expect with this setup and I'm thinking of allowing the other uBitx project in the works to fill that purpose, and set up the current project as a mono band mobile with the earlier, proved antenna. We will see.
Watch out for us "cagers" while out riding.? Some of us try to do our part.
-Ted K3RTA Newark, DE? USA
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David Posthuma
Ted