Re: Many uBitx's have reduced power on 40m CW
Evan
I am looking forward to your results with your v4, but indeed do enjoy the significant holiday with your family, no rush.?
I do think those with a pronounced dip are rare in v4. Look for Ashhar's post on the intentional equalization network, and perhaps remove its effect if you want to see root cause, which I perceive is even more variation in output power across the bands. We tested each of our rigs for output power and spurious on cw and ssb, the latter using an audio signal generator. Whether the largest unit to unit variation is the driver or PA I don't know.?
Unless you have modified it for spurious, I anticipate you may be out on a few bands for harmonics, and likely have significant ssb spurs in upper HF. I am curious what your equipment sees as I want to get at least a tiny SA, if not both your instruments. If you attack the ssb spur I am most curious.?
I am not aware of anyone introducing an alc circuit, but wonder at the impact. Some have noted poor audio drive, but mine works nicely without speech processing using an old Kenwood HT speaker mike.?
No hurry much to enjoy.
Curt
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Re: S Meter max with Nextion and CEC V 1.2
You may have something there, Kobus. I wondered if the AGC operating back in the IF stages would limit things such that an S-meter reading audio level would always drop back to something lower, especially on strong signals. In my case I used an audio AGC that followed the high-side volume control tap and it and the S-meter read the same voltage such that the input voltage is not reduced by the AGC action. I bet that's it!
=Vic=
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Re: S Meter max with Nextion and CEC V 1.2
J,
What you are measuring is the voltage needed to bias the RF input MOSFETs to keep a given signal at the audio volume control.? This will vary with signal strength so that an S9+10 signal should take a higher AGC voltage to keep a given signal strength at the volume control.? It is measuring the feedback signal level, not the actual input signal.? This is how most level meters work as far as I know.
My testing of the AGC with both the Kit-Projects and the LM358 as input says that the scaling is what will drive the signal level.? The 2 setting for the low and the 200 for the highest seems too large of a spread.? I believe that it was more like 10 to 120 as the max in the implementation that I did.? Again, the ADC monitoring function of the Nextion display is the best way to verify what is going on for a specific implementation.? Just be sure to take into account the scaling that the software is doing (divide by 4).
73
Evan
AC9TU??
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Re: S Meter max with Nextion and CEC V 1.2
Just a thought. The audio level is tapped off from the output of the agc board. Meaning that the agc will be attuniating a signal over S9 therefore it tops off at S9. If you want to read the real signal strength then you should tap the signal off at the input to the agc board. I have not yet experiment with this idee yet. J van der Merwe
Justin,
If you have a Nextion display, have you tried monitoring the ADC as Ian (KD8CEC) does in this blog:
It might give you some more information to figure out if it is a sensor or software issue.
I did the LM358 sensor modification for a friend on a v6 ?BITX.? Since all of the audio signals and controls are on the mainboard, the audio header is open.? I used that to mount a small board with the LM358 opamp as in this picture:
Just a suggestion and some more information.
73
Evan
AC9TU
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Re: S Meter max with Nextion and CEC V 1.2
Justin, If you have a Nextion display, have you tried monitoring the ADC as Ian (KD8CEC) does in this blog: It might give you some more information to figure out if it is a sensor or software issue. I did the LM358 sensor modification for a friend on a v6 ?BITX.? Since all of the audio signals and controls are on the mainboard, the audio header is open.? I used that to mount a small board with the LM358 opamp as in this picture:  Just a suggestion and some more information. 73 Evan AC9TU
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Re: Many uBitx's have reduced power on 40m CW
Jerry and Curt,
Like Jerry, my main reason for pursuing the 40meter CW dip is to understand the root cause.? I do not really use CW, so it is not that I want to operate in that mode so fixing it with Q90 gain does not really meet my need.? It is that I have noticed a pattern that I am trying to understand, as well as verify that it is a pattern and not a figment of my imagination.
I had read the original thread on working to even out the power on all of the bands.? I had read Curt's post before, I had just forgotten it, and as Jerry pointed out, it is a fix and not really the root cause at least as far as the scope traces I have made are pointing out.
My plan of attack later today is to first see if my one "parts" / experimental v4 has exactly the same issue.? It is already in a state that makes it easier to dissect and probe.? If that is the case, then I will proceed to the steps that Jerry has laid out to try to see if it is a mixer termination issue.? I also want to verify that the SSB power measurements did not give 40meters a higher power reading due to any spurious signals associated with the 40meter mixer sensitivity to the CW unbalancing.? I do not have a Rigol/Siglent level of a spectrum analyzer.? Only a TinySA for harmonics and an RSP1A with SA software for close-in spurs and IMD measurements.?
It might take more than a day or two to go through the testing, so my next post on the topic might be after Easter.? Last-minute requests by kids and family have again changed my schedule and plans.
Thank you both for all of the insights that you have given me.? This is FUN!
73
Evan
AC9TU
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Re: Many uBitx's have reduced power on 40m CW
Curt,
Ah, good.
You have a v3 or v4.
Was thinking you had a v5 or v6.
And that there might be an issue with current rigs not meeting regulations.
So at this point, there is nothing I am especially worried about.
Just curious about the root cause of the slightly low output power on 40m CW.
Note that this does not effect SSB operation.
Jerry, KE7ER
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On Thu, Apr 1, 2021 at 07:21 PM, Curt wrote:
Jerry
On my v4 all harmonics are clean, thanks to installing one of Gordon's relay boards.? But as with many v3 and v4 I have those fixed frequency leakage spurs in the vicinity of 12 meters. Attempts to remedy it with an LC or extra 45 MHz crystal stage have been futile with negative impact to cw operation. Now how well my yagi might provide some helpful dBs is conjecture without a measurement from a local ham. My rig hasn't seen a spectrum analyzer since before the pandemic, but I imagine it hasn't improved.?
73 Curt
?
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Re: Many uBitx's have reduced power on 40m CW
Jerry
On my v4 all harmonics are clean, thanks to installing one of Gordon's relay boards.? But as with many v3 and v4 I have those fixed frequency leakage spurs in the vicinity of 12 meters. Attempts to remedy it with an LC or extra 45 MHz crystal stage have been futile with negative impact to cw operation. Now how well my yagi might provide some helpful dBs is conjecture without a measurement from a local ham. My rig hasn't seen a spectrum analyzer since before the pandemic, but I imagine it hasn't improved.?
73 Curt
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Re: Many uBitx's have reduced power on 40m CW
Curt,
Agreed, if rig is compliant on all bands and modes with the increased gain at Q90, it's a good fix.
But Evan's scope traces at TP1 for 40m vs 30m and 80m make me?curious as to exactly what's going on.
Too much gain at Q90 could bring on IMD when operating SSB,
this may be hard to quantify without a good spectrum analyzer.
If present, it will cause interference in adjacent channels.
Not too big a deal at QRP power levels, but some are using their uBitx with a fairly big linear.
?
>? compliant on all CW bands and not as good in upper bands on CW. I had thought v5 and v6 were cured in this regard
So upper bands were compliant, but not quite as good in what way?
Just lower power out?? Harmonics present but within regulations?
Jerry, KE7ER
On Thu, Apr 1, 2021 at 06:10 PM, Curt wrote:
Jerry
Thanks for finding my info related to a 40m dip and remedy with a capacitor value change. We did a local group build of v4, and out of about 2 dozen units only 2 reported this issue that occurs only on cw. Wait, many of those builders don't do CW, but still I think this is a minority issue. Ashhar himself provided the clue on the equalization network after I drove myself silly trying the find the cause.?
Any spectral uncleanness is not in my judgment directly related, but the adjacent circuitry around the final transmit mixer does collect whatever RF is leaking around, but in my case my rig is compliant on all CW bands and not as good in upper bands on CW. I had thought v5 and v6 were cured in this regard. Of course we realize a distorted sine wave means other frequencies are represented, but of course higher ones are reduced by the low pass filter.?
73 curt
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Re: S Meter max with Nextion and CEC V 1.2
Vic - I have the same results with your cal values as I did mine - they were pretty close except for last two.? I guess maybe this is what we have unless a different sensor is used like Ian's sensor on his page.? At least I know it's not just me!
Zvika - not sure what to do at this point other than changing to Ian's LM358 based sensor or going to a second Nano.? I may just live with it!
73,
Justin B.
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Re: Many uBitx's have reduced power on 40m CW
Jerry
Thanks for finding my info related to a 40m dip and remedy with a capacitor value change. We did a local group build of v4, and out of about 2 dozen units only 2 reported this issue that occurs only on cw. Wait, many of those builders don't do CW, but still I think this is a minority issue. Ashhar himself provided the clue on the equalization network after I drove myself silly trying the find the cause.?
Any spectral uncleanness is not in my judgment directly related, but the adjacent circuitry around the final transmit mixer does collect whatever RF is leaking around, but in my case my rig is compliant on all CW bands and not as good in upper bands on CW. I had thought v5 and v6 were cured in this regard. Of course we realize a distorted sine wave means other frequencies are represented, but of course higher ones are reduced by the low pass filter.?
73 curt
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Mike I used an LM2596 dc to dc converter to drop the 13.8 vdc from P1 to 5vdc It¡¯s rated to 3a. I use it to feed my TDA 2030a audio amp, my SSM 2167 mic preamp/compressor and theRaduino ?board.
I bent the raduino1 pin 4 up so it doesn¡¯t set into the socket thus isolating the 13.8 supply from the raduino board.
seems to work well. I did put a choke on the 5vdc output wire and I don¡¯t have a problem with RF noise.
--
73
Mick VA3EPM
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Re: FS: Bitx40 x 2 Kanga Foxx-3 40m
Bitx40's Sold pending funds
Foxx-3 Still for grabs
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Re: Many uBitx's have reduced power on 40m CW
I'll finish off the move to this new thread by copying over news of the C81 fix from Curt:
From post 87380:
Looks like Curt added 330pf across C81 and got good results: ? ?? /g/BITX20/message/84646? ?? /g/BITX20/topic/70906819#80608I'm very curious what TP1 looks like after this fix, I doubt it's any cleaner. Would feel better if we can find the root problem rather than just boost the high frequency gain of Q90 up to whatever that poor little 2n3904 has to offer. Increasing that gain will also boost any crud at TP1. On the other hand, the crud appears to be all harmonics of 40m, so it may not matter much. Jerry, KE7ER From post 87376: I am thinking it may be the equalizer network, but surprised you would see it on all 4 units. On mine a capacitor adjustment cured it, I was searching in all the wrong places. I had a pronounced dip on 40m.? Search on my call and you should find this cap in question. I think its in the driver to the PA and only affects cw output.?? Curt wb8yyy
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Re: S Meter max with Nextion and CEC V 1.2
Hi,
I calibrated it, played with the values and have same challenge - Meter will not go over 9.
Not sure if it is the sw or the Nextion file.
--
Zvika?
4Z1ZV
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Re: Many uBitx's have reduced power on 40m CW
Jerry,
First, thank you for porting the conversation to a new thread/hashtag.? The only clarification is that I also have seen the CW power reduced on my v5 ?BITX.? So I personally have experience with 6 rigs, 3 different versions, that all exhibit reduced power on 40meters when compared to either 30 or 20 meters.? Those are 2 v4, one v5, and one v6 that I own and I have worked on 2 other ?BITX that had the issue as well; a v4 and a v6.? I have also seen posts on this board from others that have the same issue.
To answer your question, the top two pictures in post 87369 were at TP2 with the drive (RV1) at full and at minimum on 40meters.? That is showing that I have some coupling through the scope probe, hence I moved to TP1 where the probe is further from the finals.? There the signal did not change with an adjustment of RV1.? There also is the problem with a distorted 40meter signal when compared to a 30meter signal that is the strongest when in CW mode.
As stated in the prior thread it will be tomorrow at the earliest that I will be able to get to removing L31 and terminating with a 50ohm resistor to see if it is reflected signal from the connection/filter output of the BiDi amp.
Again, Thank you Jerry for your help.
73
Evan
AC9TU
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Looks like Curt added 330pf across C81 and got good results: ? ?? /g/BITX20/message/84646? ?? /g/BITX20/topic/70906819#80608I'm very curious what TP1 looks like after this fix, I doubt it's any cleaner. Would feel better if we can find the root problem rather than just boost the high frequency gain of Q90 up to whatever that poor little 2n3904 has to offer. Increasing that gain will also boost any crud at TP1. On the other hand, the crud appears to be all harmonics of 40m, so it may not matter much. Jerry, KE7ER
On Thu, Apr 1, 2021 at 08:57 AM, Jerry Gaffke wrote:
Curt,
What "equalizer network".
Is that in the emitter leg of Q90?
Can you give a pointer to your post?
But why does his scope trace show TP1 to be so ugly?
Jerry, KE7ER
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Jerry and Evan
Hashtags are not really necessary.? Common thinking is that they help
to aggregate common content, but in this case it probably does not
matter.? Oct 13, 2014 ¡ª Hashtags are words that start with '#'. In the case of Groups.io,
they only apply to the subject of a message. So, if you send a message to your
group with the subject 'This is a sample message #test', the message will be
categorized with the hashtag '#test'. You can search the archives by hashtags.
Arv _._
Evan,
I totally ignore hashtags, didn't even notice they were present.
Go ahead and edit my new thread name at will.
I've dug out my v3, will see if it exhibits the same problem.
Primary task here today is to figure out a cheap but sensitive diode RF probe
for looking at the very weak signals in the IF stages for a debug procedure I intend to write.
I believe this can be done with a 1n5711, plus a microamp of forward bias
across the diode from an optional battery.
However, it's a beautiful day.
May get distracted.
Jerry, KE7ER
On Thu, Apr 1, 2021 at 08:46 AM, Arv Evans wrote:
You might want to start a new hashtagged thread and either point
to the URL where earlier pictures reside, or copy those pictures into
your first post with the new topic name.
?
Arv
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Curt,
What "equalizer network".
Is that in the emitter leg of Q90?
Can you give a pointer to your post?
But why does his scope trace show TP1 to be so ugly?
Jerry, KE7ER
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Show quoted text
On Thu, Apr 1, 2021 at 08:49 AM, Curt wrote:
Evan
I am thinking it may be the equalizer network, but surprised you would see it on all 4 units. On mine a capacitor adjustment cured it, I was searching in all the wrong places. I had a pronounced dip on 40m.? Search on my call and you should find this cap in question. I think its in the driver to the PA and only affects cw output.??
Curt wb8yyy
?
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Evan,
I totally ignore hashtags, didn't even notice they were present.
Go ahead and edit my new thread name at will.
I've dug out my v3, will see if it exhibits the same problem.
Primary task here today is to figure out a cheap but sensitive diode RF probe
for looking at the very weak signals in the IF stages for a debug procedure I intend to write.
I believe this can be done with a 1n5711, plus a microamp of forward bias
across the diode from an optional battery.
However, it's a beautiful day.
May get distracted.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Thu, Apr 1, 2021 at 08:46 AM, Arv Evans wrote:
You might want to start a new hashtagged thread and either point
to the URL where earlier pictures reside, or copy those pictures into
your first post with the new topic name.
?
Arv
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Vic WA4THR
Kobus ZS6CHK
Mick
N8DAH
Zvi Segal