Allison,
Are you referring to my suggestion of unbalancing the D3,D4 mixer,? CLK2=VFO, CLK1=45mhz, CLK0=dead??
Given the 45mhz crystal filter, there should then be only 45mhz energy present going into the D1,D2 mixer signal port.
And if that 45mhz sine wave is of low enough level, the primary product out of the D1,D2 mixer will?
be a sine wave at the transmit frequency.? ?
Plus some higher frequency stuff that gets stripped out by the 30mhz LPF.
And a bunch of crud from secondary mixer products and harmonics in the 45mhz IF and coupling from the PA.
But by unbalancing D3,D4 for CW transmit, we should get a CW signal that's as clean as SSB with regard to harmonics.
And be cleaner and simpler than messing with injecting an audio tone.
Jerry, KE7ER
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On Mon, Mar 4, 2019 at 11:48 AM, ajparent1/KB1GMX wrote:
The problem is the source is square and the DBM is being used for a switch.
That means the output is square.? AS to CW it works better than the old pump
in a tone and can be clean with the exception of managing harmonics.
In the old days and even now the tube rigs with SI5351 as a synthetic crystal
is clean, why?? Tubes are not fast they make lousy square waves even when
fed them.? that and many of the radios have tuned circuits before the final and
the output is tuned.? OFten if you qsy across them band touching up the tuning
is required.? ?That is what selectivity and tuning does for us and too us.
Modern radios are wide band amps that will make efforts to reproduce what
they were fed.? So the basic solution is still, filters, lacking that, a very clean
source.? Alas the uBitx has a square wave source and no way to clean up
before the amp, a hole is there to fill.
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to fix this more fully:
Switchable filters to replace? the 33mhz? existing one L1-4.
for the 3.5- 5mhz range a low pass filter with cutoff of 6mhz
for the 7- 10mhz range a low pass filter with cutoff of 11mhz
for the 11- 19mhz range a low pass filter with cutoff of 20mhz
for the 20- 29.9mhz range a High pass filter with cutoff of 20mhz
***Note for this range that helps but a band pass for 21mhz and a
wide band pass for 24-29mhz would also be a better way (clean ssb).
Either way 4 to 5 filters greatly clean up signals.
The 33mhz filter delete it.
Why would this work?? The RF source tends to be biased toward greater third
harmonic for CW so putting effort into the second harmonic reduction for a filter
is not required.? The result is a modest 15db reduction of third harmonic and
spurs into the PA would clean up many if not all of the offending signals.?
Good filters will with good switching can achieve more.
Since the work is being down at low power levels (sub 1 milliwatt) SMD inductors
and capacitors will be adequate.? Switching can be done with diodes or relays.
The problem is space and simply doing it.? The board space is limited however
the underside is totally unused.
Allison
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Jerry,
The problem is the source is square and the DBM is being used for a switch.
That means the output is square.? AS to CW it works better than the old pump
in a tone and can be clean with the exception of managing harmonics.
In the old days and even now the tube rigs with SI5351 as a synthetic crystal
is clean, why?? Tubes are not fast they make lousy square waves even when
fed them.? that and many of the radios have tuned circuits before the final and
the output is tuned.? OFten if you qsy across them band touching up the tuning
is required.? ?That is what selectivity and tuning does for us and too us.
Modern radios are wide band amps that will make efforts to reproduce what
they were fed.? So the basic solution is still, filters, lacking that, a very clean
source.? Alas the uBitx has a square wave source and no way to clean up
before the amp, a hole is there to fill.
Allison
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Unfortunately, they went and outlawed spark in 1929.? ? ;-)
Jerry
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On Mon, Mar 4, 2019 at 11:28 AM, bill wright wrote:
use an old noise generator.? that is a very broadband signal
you can probably tailor it to the HF band
73 kd5yyk
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I use an old noise generator.? that is a very broadband signal you can probably tailor it to the HF band 73 kd5yyk
On Monday, March 4, 2019, 11:46:12 AM CST, Jim Sheldon <w0eb@...> wrote:
Not enough coffee this morning Jerry,? However, there is NO way to create a "pseudo sine wave" that will cover that frequency spread (1.8 to 30 MHz) with the current setup and Jerry's right, the only way is to use proper LPF filtering for all the bands. ?Unfortunately the 4 supplied are too broad to do the job properly and with only the supplied # of relays, it's not possible to switch extra ones in and out to achieve the desired results without some serious cut/paste modifications to even the V5 uBITX board.
Jim
------ Original Message ------
Sent: 3/4/2019 11:10:13 AM
Subject: Re: [BITX20] Pseudo-Sine?
You have that backwards.
CLK2 goes into the mixer at D1,D2, and is at the CW operating frequency.
CLK0 and CLK1 are dead in the water when transmitting CW.
Class C power amps are how most CW-only transmitters have worked over the last 100 years
Class C creates?a big honking square wave that then needs to be sorted out by effective low pass filters.
The solution for the uBitx is simple enough, make the transmit LPF's work properly.
Unfortunately, the relays are kind of tough for some of us to work on,
and few can be bothered to measure the results.
Jerry, KE7ER
On Mon, Mar 4, 2019 at 08:49 AM, Jim Sheldon wrote:
I don't believe that will work as CLK02 is not used for CW transmit. CLK01 produces "ON FREQUENCY OF TRANSMISSION RF (square waves) for CW
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I believe Allison has found that the four transmit LPF's are adequate.
It is the board routing imposed by using the minimum possible number of relays?
that is allowing those harmonics to sneak through.
Using more expensive relays designed for use at RF can also help.
Since this is primarily an SSB rig with CW as an afterthought, I don't think we can complain too much.
As I see it, the intent is to provide a minimum usable rig to encourage tinkerers to tinker and learn,
and in this it succeeds.? The tinkering required to move CW keying to the D3,D4 mixer should be
quite interesting and easy to do.?
If you want proper CW operation, your next project is clean electronic QSK.? ?;-)
Jerry, KE7ER
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On Mon, Mar 4, 2019 at 09:46 AM, Jim Sheldon wrote:
Unfortunately the 4 supplied are too broad to do the job properly and with only the supplied # of relays, it's not possible to switch extra ones in and out to achieve the desired results without some serious cut/paste modifications to even the V5 uBITX board.
?
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Most attempts at transmitting CW on *Bitx* variants over the last 15 years have involved?
injecting an audio tone into the mike input.
Ideally, the result is indeed exactly the same as any other CW transmission.
This forum goes back to 2004, lots of examples of injecting an audio tone for CW right here.
But unbalancing a mixer should give better results.
Either unbalance mixer D1,D2 with CLK2=TransmitFreq? and CLK1=CLK0=dead as on the stock uBitx,
or unbalance mixer D3,D4 with CLK2=VFO,? CLK1=45mhz, CLK0=dead as I just proposed.
Better results because:
? ? No close in crap due to distortion in your audio oscillator, mike amp, or modulator
? ? No opposite sideband due to a not quite perfect crystal filter
? ? No residual carrier due to a not quite balanced modulator and a not quite perfect crystal filter.
? ? It's much simpler to implement
The first three issues are unavoidable for SSB transmissions given this architecture.
But easily avoided when transmitting CW, by way of shutting down the modulator (CLK0=dead) and unbalancing a mixer.
On the other hand, this is primarily a QRP SSB rig.
Less than ideal CW operation may be acceptable for some if not using an external power amp.
Have at it as you see fit.
Jerry, KE7ER
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On Mon, Mar 4, 2019 at 10:18 AM, Evan Hand wrote:
When I tested the SSB harmonic performance with a single audio tone, it looked to me like a CW carrier. I also noted that the harmonics were much lower using the full SSB path.? Is a simple solution to create a pure audio tone that is keyed with the PTT signal line?? The built in side tone generator would need to be significantly filtered to make it into a clean sine wave.
Just an idea, not really into CW myself (at least at this point).
73
Evan
AC9TU
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When I tested the SSB harmonic performance with a single audio tone, it looked to me like a CW carrier. I also noted that the harmonics were much lower using the full SSB path.? Is a simple solution to create a pure audio tone that is keyed with the PTT signal line?? The built in side tone generator would need to be significantly filtered to make it into a clean sine wave.
Just an idea, not really into CW myself (at least at this point).
73
Evan
AC9TU
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Ignore that last paragraph of my previous post, included below.
It's garbage text.
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On Mon, Mar 4, 2019 at 10:14 AM, Jerry Gaffke wrote:
We're assuming there is no 12mhz energy present at the D3,D4 mixer (CLK0 is shut down).
And that the D3,D4 mixer is unbalanced using the CW-KEY scheme currently found at D1,D2.
Oh, and that D3,D4 attenuate CLK1 by 6dB (I'm not sure what happens when the mixer is used like that).
A CLK1 of -13dBm should get you into the ballpark,?
Jerry?
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Re: DC blocking cap between souncard and ubitc mic input.
#ft8
#ubitx
The easydigi does have this blocking cap. .1uf
Joe
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On Mar 4, 2019, at 12:05 PM, Playthatbeat Mrdj < playthatbeat303@...> wrote: So things are actually worse when using a transformer to isolate the mic line? So things like the easy-digi etc. make things worse? this was not my experience at all. before using a transformer, i could not sustain the audio connection between my (horrible) single audio jack on my handheld PC, but after i could without issue.
So, it's possible that using easy-digi or a transformer is shunting the voltage on the mic line to ground, which could cause all manner of strange problems with the uBitx? Is this correct?
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Assuming 16dB gain in the 45mhz amp and a 45mhz signal into the D1,D2 mixer
that is at least 10db down from a 7dBm CLK2 local oscillator,
the 45mhz square wave coming out of the D3,D4 mixer should be? ?7dBm-10dB-16dB = -19dBm.
Perhaps 10dB less, as CLK2 is nowhere near 7dBm.
If we overload the 45mhz signal port going into D1,D2, we start generating harmonics again.
The D3,D4 mixer would now be getting unbalanced during CW key down by moving R104,R105
over from where they have been at D1,D2.
> However, there is NO way to create a "pseudo sine wave" that will cover that frequency spread (1.8 to 30 MHz) with the current setup?
This should create a "real sine wave" from 3.5 to 30mhz, with far less harmonic energy on CW than the current scheme.?
And a whole bunch of other mixer products and coupled in crap that Allison will be happy to tell you about.?
If you want 1.8mhz, be sure to add an appropriate external transmit LPF.
Jerry, KE7ER
We're assuming there is no 12mhz energy present at the D3,D4 mixer (CLK0 is shut down).
And that the D3,D4 mixer is unbalanced using the CW-KEY scheme currently found at D1,D2.
Oh, and that D3,D4 attenuate CLK1 by 6dB (I'm not sure what happens when the mixer is used like that).
A CLK1 of -13dBm should get you into the ballpark,?
Jerry?
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On Mon, Mar 4, 2019 at 09:28 AM, Jerry Gaffke wrote:
One possibility for CW transmit would be to inject a low level keyed 45mhz square wave at CLK1,
the 45mhz crystal filter will turn that into a sine wave.
CLK2 can remain a square wave at Transmit_Freq + 45mhz, same as during SSB transmit,
the D1,D2 mixer will generate a sine wave for the power amp at the Transmit_Freq.
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Not enough coffee this morning Jerry,? However, there is NO way to create a "pseudo sine wave" that will cover that frequency spread (1.8 to 30 MHz) with the current setup and Jerry's right, the only way is to use proper LPF filtering for all the bands. ?Unfortunately the 4 supplied are too broad to do the job properly and with only the supplied # of relays, it's not possible to switch extra ones in and out to achieve the desired results without some serious cut/paste modifications to even the V5 uBITX board.
Jim
------ Original Message ------
Sent: 3/4/2019 11:10:13 AM
Subject: Re: [BITX20] Pseudo-Sine?
You have that backwards.
CLK2 goes into the mixer at D1,D2, and is at the CW operating frequency.
CLK0 and CLK1 are dead in the water when transmitting CW.
Class C power amps are how most CW-only transmitters have worked over the last 100 years
Class C creates?a big honking square wave that then needs to be sorted out by effective low pass filters.
The solution for the uBitx is simple enough, make the transmit LPF's work properly.
Unfortunately, the relays are kind of tough for some of us to work on,
and few can be bothered to measure the results.
Jerry, KE7ER
On Mon, Mar 4, 2019 at 08:49 AM, Jim Sheldon wrote:
I don't believe that will work as CLK02 is not used for CW transmit. CLK01 produces "ON FREQUENCY OF TRANSMISSION RF (square waves) for CW
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Re: How to connect ubitx microphone jack to soundcard output
The highest value capacitance, the better, I would use either a nonpolarized electrolytic or polyester caps for this audio application. Then a 1:1 dc- isolating audio or data transformer to get rid of ground loop issues. Another cap in series on the other end of the cable.
Il 04/mar/2019 18:20, "Joe Puma" < kd2nfc@...> ha scritto: What¡¯s a good value for the blocking cap? If that¡¯s the purpose of the one on the easydigi, it¡¯s value is .1uf
Joe KD2NFC? Any 600ohm 1:1 audio transformer is a very good idea. 600ohms is a typical impedance presented by headphones these days, so it's a good value to shoot for. There is a voltage present on the MIC in of the uBitx, and this will confuse most modern soundcards and laptops, maybe totally distorting the audio, but If when You plug in a headphone or mic to your computer, the operating system detects this and says something in a dialog box, You need to use AT LEAST a blocking capacitor for the MIC IN on the uBitx/Line out on the computer, but most likely a 1:1 transformer also, otherwise the connection will be very unstable. You will find the computer will switch randomly between the input jack and any built-in mic especially on a laptop, unable to sense if the jack has a load on it correctly.
If You are unlucky enough to have a SINGLE jack for BOTH mic and headphones on Your laptop/tablet - for a headset, you should get one of these
Remember the Audio out using a splitter like this, or a (green) jack on a computer itself for headphones out is also STEREO, and using a mono plug either end of a lead for this will cause problems. So, You might ALSO need one of these which you can then adapt.
Once You get things worked out, You will be very happy with the uBitx for digital - audio using cables, and control via cat (ft817 emulation) with the CEC firmware.
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One possibility for CW transmit would be to inject a low level keyed 45mhz square wave at CLK1,
the 45mhz crystal filter will turn that into a sine wave.
CLK2 can remain a square wave at Transmit_Freq + 45mhz, same as during SSB transmit,
the D1,D2 mixer will generate a sine wave for the power amp at the Transmit_Freq.
Along with a bunch of other mixer products and crap coupled from power amp into the IF amp, as usual.
Allisons extra filters would fix that, at the cost of considerable complication.
But the above simple CLK1 scheme should be sufficient to reduce harmonics during CW transmit.
Jerry, KE7ER
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On Mon, Mar 4, 2019 at 09:10 AM, Jerry Gaffke wrote:
You have that backwards.
CLK2 goes into the mixer at D1,D2, and is at the CW operating frequency.
CLK0 and CLK1 are dead in the water when transmitting CW.
Class C power amps are how most CW-only transmitters have worked over the last 100 years
Class C creates?a big honking square wave that then needs to be sorted out by effective low pass filters.
The solution for the uBitx is simple enough, make the transmit LPF's work properly.
Unfortunately, the relays are kind of tough for some of us to work on,
and few can be bothered to measure the results.
Jerry, KE7ER
toggle quoted message. . .
?
On Mon, Mar 4, 2019 at 08:49 AM, Jim Sheldon wrote:
I don't believe that will work as CLK02 is not used for CW transmit. CLK01 produces "ON FREQUENCY OF TRANSMISSION RF (square waves) for CW
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Re: How to connect ubitx microphone jack to soundcard output
What¡¯s a good value for the blocking cap? If that¡¯s the purpose of the one on the easydigi, it¡¯s value is .1uf
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On Mar 4, 2019, at 10:55 AM, Playthatbeat Mrdj < playthatbeat303@...> wrote: Any 600ohm 1:1 audio transformer is a very good idea. 600ohms is a typical impedance presented by headphones these days, so it's a good value to shoot for. There is a voltage present on the MIC in of the uBitx, and this will confuse most modern soundcards and laptops, maybe totally distorting the audio, but If when You plug in a headphone or mic to your computer, the operating system detects this and says something in a dialog box, You need to use AT LEAST a blocking capacitor for the MIC IN on the uBitx/Line out on the computer, but most likely a 1:1 transformer also, otherwise the connection will be very unstable. You will find the computer will switch randomly between the input jack and any built-in mic especially on a laptop, unable to sense if the jack has a load on it correctly.
If You are unlucky enough to have a SINGLE jack for BOTH mic and headphones on Your laptop/tablet - for a headset, you should get one of these
Remember the Audio out using a splitter like this, or a (green) jack on a computer itself for headphones out is also STEREO, and using a mono plug either end of a lead for this will cause problems. So, You might ALSO need one of these which you can then adapt.
Once You get things worked out, You will be very happy with the uBitx for digital - audio using cables, and control via cat (ft817 emulation) with the CEC firmware.
|
Re: DC blocking cap between souncard and ubitc mic input.
#ft8
#ubitx
Discussion of the microphone input and related DC isolation has been coming up for discussion
periodically ever since the first BITX design.? Best approach is to look at the schematic and that
of your input device to insure that proper isolation and level adjustment is provided.? Just making
statements about what should and should not be used probably should be backed up with "why it
works this way" explanations.?
This is not to deprecate any of the statements already made, just to suggest that what works for
XYZ rigs may not be the perfect solution for a particular version of BITX.? The BITX microphone
input circuit has changed slightly over the years.?
Arv? K7HKL _._
So things are actually worse when using a transformer to isolate the mic line? So things like the easy-digi etc. make things worse? this was not my experience at all. before using a transformer, i could not sustain the audio connection between my (horrible) single audio jack on my handheld PC, but after i could without issue.
So, it's possible that using easy-digi or a transformer is shunting the voltage on the mic line to ground, which could cause all manner of strange problems with the uBitx? Is this correct?
|
Jim,
Clock#2 is used for CW, but the frequency is adjusted to the dial setting +/- the CW tone depending on the CWU/CWL selection. Still, it is a square wave at the HF frequencies, not so at the higher frequencies for the IF mixing.(>45 MHZ). Still not a "good" sine wave, but better than the 7.0 MHz one.
I too would go for the sine wave si5351 replacement. There is the AD9834 that produces a sine wave to 75mhz.? Would need to add it to the i2C line and replace the si5351 clock#2 with this device. also need to adjust the Raduino program, and now calibrate two different devices.
Might be worth looking into.
73
Evan
AC9TU
73
Evan
AC9TU
|
You have that backwards.
CLK2 goes into the mixer at D1,D2, and is at the CW operating frequency.
CLK0 and CLK1 are dead in the water when transmitting CW.
Class C power amps are how most CW-only transmitters have worked over the last 100 years
Class C creates?a big honking square wave that then needs to be sorted out by effective low pass filters.
The solution for the uBitx is simple enough, make the transmit LPF's work properly.
Unfortunately, the relays are kind of tough for some of us to work on,
and few can be bothered to measure the results.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Mon, Mar 4, 2019 at 08:49 AM, Jim Sheldon wrote:
I don't believe that will work as CLK02 is not used for CW transmit. CLK01 produces "ON FREQUENCY OF TRANSMISSION RF (square waves) for CW
|
Re: DC blocking cap between souncard and ubitc mic input.
#ft8
#ubitx
So things are actually worse when using a transformer to isolate the mic line? So things like the easy-digi etc. make things worse? this was not my experience at all. before using a transformer, i could not sustain the audio connection between my (horrible) single audio jack on my handheld PC, but after i could without issue.
So, it's possible that using easy-digi or a transformer is shunting the voltage on the mic line to ground, which could cause all manner of strange problems with the uBitx? Is this correct?
|
I don't believe that will work as CLK02 is not used for CW transmit. CLK01 produces "ON FREQUENCY OF TRANSMISSION RF (square waves) for CW and that is where the harmonics need to be surpressed. There is no way to successfully convert CLK01 to even a pseudo sine wave over the complete 1.8-30 MHz frequency range for clean CW transmission. ??
Now, IF Silicon Labs were to produce a chip that was a pin-for-pin replacement for the Si5351a but output a sine wave instead, then I'd instantly swap out the 5351's on all my uBITX Raduino's and the TSW Raduino Clone and BITeensio cards. ?Until that happens the multiple LPF's with extra switching is about the only fix IMO.
Jim - W0EB
------ Original Message ------
Sent: 3/4/2019 10:13:33 AM
Subject: Re: [BITX20] Pseudo-Sine?
Since someone asked about an RC filter ...Logical place would be on Clk02 (45-75 Mhz)? ...as an example random/scraped from google
Double the l's and spice it ...Not simple ..There is a reason RF design engineers get paid the big bux, right?
Jim
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bill wright
Jim Sheldon