Re: Follow-up Antuino question
Ashar, I agree that a analog vfo would be superior but I have not had much luck building one that was stable enough. That was the reason I chose to use the 5351 or my PLL. Any chance you would share your vfo design with us? Barry
On Sat, Nov 14, 2020, 11:31 AM Ashhar Farhan < farhanbox@...> wrote: Barry, I too built a direct conversion transceiver a few months ago. I chose a fully analog design without any ICs. A carefully designed free running vfo is used. It is so stable that I can continuously monitor the FT8 spot! On the other hand, when I substitute it with an Si5351, the difference is immediately obvious. The CW is noiser and the SSB audio has less fidelity. I can no longer copy the signals that were barely above the noise floor. Given a choice, I would use a free running VFO any day. Except that it is very expensive to build them with a good slow motion and implementing multiband design is always a?challenge. - f
On Sat 14 Nov, 2020, 9:55 PM barry halterman, < kthreebo@...> wrote: Hi fellow DC rx fans. Back in 1992, Rick Campbell had a design in QST for a direct conversion receiver he called the R1. Later he upgraded this to the R2. I have the R1 that I have used the si5351 to drive the SBL-1 mixer with excellent results. I use a 6 db pad on the LO port, per a recommendation from Ashar. Later I changed the LO to a PLL oscillator with a sine wave output. I did not notice any difference at all between the two oscillators. The recovered audio is fantastic from this R1 board. Rick had a few different LC designs for filters, SSB narrow and wide and a cw filter.? For those who want a serious DC receiver, I highly recommend looking at his design. It is a little more complicated then just a mixer and LM386, but very well worth the effort. K3BO
Would be interesting to try sine wave vs square wave.
But I doubt you will notice much difference,
Assuming you have a low pass (or band pass) filter on the RF input,
the harmonics in a square wave should not cause any first order products in the resultant audio.
Also, your mixer is likely to have a non-linear voltage vs current relationship
at the local oscillator port anyway.
However, the clean audio one can get from a DC receiver make it?
an excellent testbed for trying this sort of thing.
And I have heard that a sine wave is somewhat preferred for driving
even a diode ring mixer, which has an extremely non-linear LO port.
Note that the Antuino has a very nice ADE-1 mixer.
Might be possible to include that in your DC receiver.
Jerry, KE7ER
On Fri, Nov 13, 2020 at 08:35 PM, Bob Lunsford wrote:
There was some comment in the webpage about the signal being a square wave. If this shows up in the signal, causing harmonics, then included in the amp should be a "smoothing" circuit or some way to make it show up as a sine wave. This is theoretically simple since an inductor's flywheel effect would actually convert it to a sine wave. How well it does this is another question and it would/could cause some refinement of the signal. A simple resistor-capacitor circuit followed by an amp may be better.
?
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Re: Follow-up Antuino question
Barry, I too built a direct conversion transceiver a few months ago. I chose a fully analog design without any ICs. A carefully designed free running vfo is used. It is so stable that I can continuously monitor the FT8 spot! On the other hand, when I substitute it with an Si5351, the difference is immediately obvious. The CW is noiser and the SSB audio has less fidelity. I can no longer copy the signals that were barely above the noise floor. Given a choice, I would use a free running VFO any day. Except that it is very expensive to build them with a good slow motion and implementing multiband design is always a?challenge. - f
On Sat 14 Nov, 2020, 9:55 PM barry halterman, < kthreebo@...> wrote: Hi fellow DC rx fans. Back in 1992, Rick Campbell had a design in QST for a direct conversion receiver he called the R1. Later he upgraded this to the R2. I have the R1 that I have used the si5351 to drive the SBL-1 mixer with excellent results. I use a 6 db pad on the LO port, per a recommendation from Ashar. Later I changed the LO to a PLL oscillator with a sine wave output. I did not notice any difference at all between the two oscillators. The recovered audio is fantastic from this R1 board. Rick had a few different LC designs for filters, SSB narrow and wide and a cw filter.? For those who want a serious DC receiver, I highly recommend looking at his design. It is a little more complicated then just a mixer and LM386, but very well worth the effort. K3BO
Would be interesting to try sine wave vs square wave.
But I doubt you will notice much difference,
Assuming you have a low pass (or band pass) filter on the RF input,
the harmonics in a square wave should not cause any first order products in the resultant audio.
Also, your mixer is likely to have a non-linear voltage vs current relationship
at the local oscillator port anyway.
However, the clean audio one can get from a DC receiver make it?
an excellent testbed for trying this sort of thing.
And I have heard that a sine wave is somewhat preferred for driving
even a diode ring mixer, which has an extremely non-linear LO port.
Note that the Antuino has a very nice ADE-1 mixer.
Might be possible to include that in your DC receiver.
Jerry, KE7ER
On Fri, Nov 13, 2020 at 08:35 PM, Bob Lunsford wrote:
There was some comment in the webpage about the signal being a square wave. If this shows up in the signal, causing harmonics, then included in the amp should be a "smoothing" circuit or some way to make it show up as a sine wave. This is theoretically simple since an inductor's flywheel effect would actually convert it to a sine wave. How well it does this is another question and it would/could cause some refinement of the signal. A simple resistor-capacitor circuit followed by an amp may be better.
?
|
Re: Follow-up Antuino question
Hi fellow DC rx fans. Back in 1992, Rick Campbell had a design in QST for a direct conversion receiver he called the R1. Later he upgraded this to the R2. I have the R1 that I have used the si5351 to drive the SBL-1 mixer with excellent results. I use a 6 db pad on the LO port, per a recommendation from Ashar. Later I changed the LO to a PLL oscillator with a sine wave output. I did not notice any difference at all between the two oscillators. The recovered audio is fantastic from this R1 board. Rick had a few different LC designs for filters, SSB narrow and wide and a cw filter.? For those who want a serious DC receiver, I highly recommend looking at his design. It is a little more complicated then just a mixer and LM386, but very well worth the effort. K3BO
Would be interesting to try sine wave vs square wave.
But I doubt you will notice much difference,
Assuming you have a low pass (or band pass) filter on the RF input,
the harmonics in a square wave should not cause any first order products in the resultant audio.
Also, your mixer is likely to have a non-linear voltage vs current relationship
at the local oscillator port anyway.
However, the clean audio one can get from a DC receiver make it?
an excellent testbed for trying this sort of thing.
And I have heard that a sine wave is somewhat preferred for driving
even a diode ring mixer, which has an extremely non-linear LO port.
Note that the Antuino has a very nice ADE-1 mixer.
Might be possible to include that in your DC receiver.
Jerry, KE7ER
On Fri, Nov 13, 2020 at 08:35 PM, Bob Lunsford wrote:
There was some comment in the webpage about the signal being a square wave. If this shows up in the signal, causing harmonics, then included in the amp should be a "smoothing" circuit or some way to make it show up as a sine wave. This is theoretically simple since an inductor's flywheel effect would actually convert it to a sine wave. How well it does this is another question and it would/could cause some refinement of the signal. A simple resistor-capacitor circuit followed by an amp may be better.
?
|
Re: An English site of a French HAM, with interesting information about Ubitx.
Thanks, Evan, you¡¯re always on the cutting edge of information.
I note this aside for my next changes
Have a good weekend
|
Thanks Evan for the help.
I had been searching the CEC sketch instead.
My TXR already uses a 2X16 display and I was hoping to upgrade to the Nextion.
My TXR uses 2 swithced? 2nd IF oscillators for the sidebands.
I may upload some photos of my radio later for those interested.
I will keep playing!
many thanks
Richard? VA3NDO
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Re: Follow-up Antuino question
Bob: My spare Raduino worked fine for that purpose feeding a 4SQRP ZZRX-40 DC receiver. Heard all states from Florida on an indoor wire.
James KE4MIQ
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Re: An English site of a French HAM, with interesting information about Ubitx.
Gerard,
I went back and looked again.? I believe that F5NPV is also using the standalone signal analyzer option from KD8CEC.? That is a second Nano connected via the I2C lines to provide the "small scanner" as well as some other features.? The code in the Raduino Nano would be UBITX_CEC_V1.200_NX_S.hex.? There is then another program for the second Nano.? Here is the KD8CEC page that describes it:
73
Evan
AC9TU
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Re: An English site of a French HAM, with interesting information about Ubitx.
Hello,
Thanks
An other link
cdt?
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Re: An English site of a French HAM, with interesting information about Ubitx.
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Re: Follow-up Antuino question
Would be interesting to try sine wave vs square wave.
But I doubt you will notice much difference,
Assuming you have a low pass (or band pass) filter on the RF input,
the harmonics in a square wave should not cause any first order products in the resultant audio.
Also, your mixer is likely to have a non-linear voltage vs current relationship
at the local oscillator port anyway.
However, the clean audio one can get from a DC receiver make it?
an excellent testbed for trying this sort of thing.
And I have heard that a sine wave is somewhat preferred for driving
even a diode ring mixer, which has an extremely non-linear LO port.
Note that the Antuino has a very nice ADE-1 mixer.
Might be possible to include that in your DC receiver.
Jerry, KE7ER
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Show quoted text
On Fri, Nov 13, 2020 at 08:35 PM, Bob Lunsford wrote:
There was some comment in the webpage about the signal being a square wave. If this shows up in the signal, causing harmonics, then included in the amp should be a "smoothing" circuit or some way to make it show up as a sine wave. This is theoretically simple since an inductor's flywheel effect would actually convert it to a sine wave. How well it does this is another question and it would/could cause some refinement of the signal. A simple resistor-capacitor circuit followed by an amp may be better.
?
|
Re: Follow-up Antuino question
There was some comment in the webpage about the signal being a square wave. If this shows up in the signal, causing harmonics, then included in the amp should be a "smoothing" circuit or some way to make it show up as a sine wave. This is theoretically simple since an inductor's flywheel effect would actually convert it to a sine wave. How well it does this is another question and it would/could cause some refinement of the signal. A simple resistor-capacitor circuit followed by an amp may be better.
Still thinking about it.
Bob ¡ª KK5R
On Friday, November 13, 2020, 11:22:05 PM EST, Ashhar Farhan <farhanbox@...> wrote:
bob,? i have used it as a local oscillator. but there is a catch The primary purpose of the RF out was to be able to measure the frequency response by feeding?the RF out into the device/circuit under test and measuring the output through the RF-In jack. Hence, the RF output is low, about -20 dbm. This is insufficient?to drive a mixer. There are two ways to fix this 1. You can remove the three attenuator resistors from the RF out pad and directly get about?+10 dbm from the RF out jack. This can damage?the RF In if fed directly. You can build an outboard attenuator for similar to the original RF out attenuator, but remember to use it each time you are testing a device. 2. You can build a two-stage Feedback amplifier with about 16 db gain in each stage with a 6 db attenuator pad between the two stages to provide a useful block of 26 db gain. This circuit will be useful in many other places as well. Use this to boost the RF output to the level needed by the mixer.
- f?
On Sat, Nov 14, 2020 at 8:58 AM Bob Lunsford via <nocrud222= [email protected]> wrote: After rereading the specifications for the Antuino and its oscillator stability, I suddenly wondered if the
oscillator can be used for the oscillator in a Direct Conversion
receiver... Perhaps there is a way to set it up that the antenna jack can be the source for the oscillator signal.
The Antuino has a digital readout and this promises
(theoretically) to be a shortcut and result in an excellent signal
oscillator for a DC receiver. A mixer and an LM-386 audio amp and the
receiver would be simplified and made much superior to an LC
controlled oscillator plus make it usable for a full range of
frequencies. Has anyone considered doing this?
Bob ¡ª KK5R
|
Re: Follow-up Antuino question
bob,? i have used it as a local oscillator. but there is a catch The primary purpose of the RF out was to be able to measure the frequency response by feeding?the RF out into the device/circuit under test and measuring the output through the RF-In jack. Hence, the RF output is low, about -20 dbm. This is insufficient?to drive a mixer. There are two ways to fix this 1. You can remove the three attenuator resistors from the RF out pad and directly get about?+10 dbm from the RF out jack. This can damage?the RF In if fed directly. You can build an outboard attenuator for similar to the original RF out attenuator, but remember to use it each time you are testing a device. 2. You can build a two-stage Feedback amplifier with about 16 db gain in each stage with a 6 db attenuator pad between the two stages to provide a useful block of 26 db gain. This circuit will be useful in many other places as well. Use this to boost the RF output to the level needed by the mixer.
- f?
On Sat, Nov 14, 2020 at 8:58 AM Bob Lunsford via <nocrud222= [email protected]> wrote: After rereading the specifications for the Antuino and its oscillator stability, I suddenly wondered if the
oscillator can be used for the oscillator in a Direct Conversion
receiver... Perhaps there is a way to set it up that the antenna jack can be the source for the oscillator signal.
The Antuino has a digital readout and this promises
(theoretically) to be a shortcut and result in an excellent signal
oscillator for a DC receiver. A mixer and an LM-386 audio amp and the
receiver would be simplified and made much superior to an LC
controlled oscillator plus make it usable for a full range of
frequencies. Has anyone considered doing this?
Bob ¡ª KK5R
|
Follow-up Antuino question
After rereading the specifications for the Antuino and its oscillator stability, I suddenly wondered if the
oscillator can be used for the oscillator in a Direct Conversion
receiver... Perhaps there is a way to set it up that the antenna jack can be the source for the oscillator signal.
The Antuino has a digital readout and this promises
(theoretically) to be a shortcut and result in an excellent signal
oscillator for a DC receiver. A mixer and an LM-386 audio amp and the
receiver would be simplified and made much superior to an LC
controlled oscillator plus make it usable for a full range of
frequencies. Has anyone considered doing this?
Bob ¡ª KK5R
|
Good news. Thanks. That's a clincher for me.
Bob ¡ª KK5R
On Friday, November 13, 2020, 10:10:57 PM EST, Evan Hand <elhandjr@...> wrote:
My Antuino came fully assembled in the enclosure shown.? The screen may be different depending on the version of software that is now being supplied by HF Signals
73
Evan
AC9TU
|
My Antuino came fully assembled in the enclosure shown.? The screen may be different depending on the version of software that is now being supplied by HF Signals
73
Evan
AC9TU
|
I am preparing to order the Antuino. I wonder if it comes as shown in the image on the web page (in a box) or does it come as shown in the Calibration section...
I'm hoping it comes as shown below OR if a box is offered as an extra.
Bob ¡ª KK5R
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Re: Mic bleed into audio during TX
Thanks Evan, I¡¯ll look into that -- ?
73
Mick VA3EPM?
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Re: Mic bleed into audio during TX
I had this issue with all of my uBITX.? It started as very bad RF feedback, that I was able to reduce through proper grounding.? I traced it to RF getting into the shack on the coax shield.? Installed 4 ferrites before the coax goes into the shack and that seemed to solve it.? A common mode choke might have been a better solution.
I would look to RF in the shack getting into the audio of the uBITX.
73
Evan
AC9TU
|
Mic bleed into audio during TX
I¡¯m recently hearing my mic in my headphones during transmit. All my reports indicate a good audio reception from others So it doesn¡¯t seem to affect my transmit audio. Has anyone experienced this? Looking at the schematic I wonder about the contacts (M1 M2) being stuck on K3 but I¡¯m reluctant to tear apart my recently mounted in a box radio. -- ?
73
Mick VA3EPM?
|
Sure seems to me that it would be a lot easier to make several littler boards to provide better shield ing between stages. ? Put the amplifier off by itself as a module. ? Try to deal with the skinny/longer trace issues. ? There might be a way to use more than one SI 5351 so you could avoid some of the cross talk. ? ?Add in a physical mode switch so you can solve the thorny CW offset issues, by knowing for certain which mode is requested BEFORE The key is pressed. ?
By adding in a duplicate receiver portion, and some diode switching, you might make a full break in CW Station.?
I¡¯m just talking out of my head but I bet some people know how to do all of this easily.?
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On Nov 13, 2020, at 18:13, Jerry Gaffke via groups.io <jgaffke@...> wrote:
?Fritzing is apparently easy for a beginner to get started, but limited.
For example, a max of 2 layers.? It does create gerbers.
If you prefer a standard C tool chain over the Arduino IDE,?
you may not like Fritzing.
gEDA is worth a look, it's a powerful set of tools.
I've concluded that for my needs, it's either Kicad or gEDA.
Kicad is moving forward with new releases, gEDA is not.
Though if gEDA is good enough, that might be a good thing.
I'm not impressed by the 3D models some packages offer.
Perhaps if I was designing something really tight and complex
in all three dimensions, like a cell phone.? But otherwise that 3D stuff
is mostly just eye candy, and a huge waste of disk space.
Creating netlists can be done with any schematic editor, that's
a separate process from laying out a board.? Creating a netlist by hand
in a text editor can be faster than doing it in a schematic editor.
A python script to reduce a hierarchical circuit description in?ASCII text
to a netlist would be fun and easy to create.
A visual representation can be helpful, especially with analog circuits.
But ASCII text is a lot more malleable, a couple decades of writing VHDL
for FPGA firmware has made me quite comfortable with just text as a way
of describing a hardware design.
Jerry, KE7ER
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Gerard
F5NPV
Bob Lunsford
Mick