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Re: BITX QSO Night, Sunday, December 10, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere

John P
 

I'll try to be on again at 3PM EST (2000 UTC). Hopefully I won't fall asleep on the couch this week and actually make it on the air by 3! That worked out well last week!
--
John - WA2FZW
BITX QSO Night, Sunday, December 10, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere

John P
 

BITX QSO Night, Sunday, December 10, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere

Join us as we make contacts from BITX40 to BITX40 on 7.277 MHz in 40 meters!

This is a worldwide event for BITX40 stations starting at 7pm in each time zone. To participate, call CQ BITX on Sunday, starting at 7pm your local time. The BITX QSO Night continues through the evening and conditions usually improve after sunset, so it is worthwhile to participate later in the evening.

Suggested Best Operating Practices:

Work at QRP power levels unless conditions require more power.
Call and listen for CQ BITX on the hour and every quarter hour.
It is helpful if you call CQ BITX with your callsign, name and location.?
Repeat your callsign a number of times during your CQ BITX and during QSO's.
Start a QSO by confirming the callsign, location, name and signal report of the other operator.
Say the callsign, name and location of the other operator so others can hear.
If the frequency is busy, avoid long conversations.
After your initial QSO is complete, ask if there are any other stations who would like to contact.

Report your QSO's, discuss propagation, noise, signal reports, audio reports, antenna type, etc. in this thread.

This is an undirected, scheduled event.? The BITX QSO Night relies on you to call CQ BITX to initiate contacts with other stations, so warm up that final and transmit a few calls on Sunday evening.? Talk to you then!
--
John - WA2FZW
Re: ubitx circuit, wiring, source code on github

 

I'm not quite sure what this means.
Is this only a problem when attempting to receive a 12.000 mhz signal?
I can see where receiving 12mhz may be problematic, though I don't plan to be operating there much.

Yes, there are all kinds of unwanted products from the mixers flying about, especially since we don't have any shielding.
I'm willing to live with a few birds given the likely price point and capabilities and hackability of this rig.
Should be a fun to try to figure out where they are coming from.

Jerry, KE7ER


On Thu, Dec 7, 2017 at 12:35 pm, Henning Weddig wrote:

a similar situation will happen under "nromal conditions: the first mixer never is fully balanced resulting that receiving 12 MHz, tehre will be an attenuated 57 Mhz signal from the frist LO at the output of the first mixer besides the wanted? 45 MHz... we will have a big spur at 12 MHz antenna signal?!

Re: CAT control of the bitx frequency

 

On Thu, Dec 7, 2017 at 06:23 am, Karl Heinz Kremer, K5KHK wrote:
Ashhar, here is information about how the Arduino's are getting reset by?the serial port:?

The DTR line is connected (via a capacitor) to the Arduino reset input (you an see this on the Nano schematic:?). Based on the "Reset" information from above, you should be able to prevent this reset by adding a resistor between "Reset" and +5V - this will however also prevent the Arduino from being programmed automatically, and you will have to trigger a normal reset by pushing the reset button on the Nano board.?
Most of the "Disabling Auto Reset" discussion was related to Uno's.? If you look at the Nano schematic, you will see that there is already a 1K resistor between "Reset" and +5V (it's connected at the "Reset" pushbutton switch).

The DTR output of the USB chip connects to "Reset" thru C4.? Tombstoning C4 should disable the Auto Reset.? Adding an SPST switch between the now open C4 pad and the now unconnected terminal on the tombstoned C4 will allow you to get the Auto Reset back later if you want it.? Switch open - no AutoReset, switch closed - AutoReset enabled.

73,
Carl? K0MWC
Re: ubitx circuit, wiring, source code on github

 

Farhan,

You've actually done this stuff, and I'm just engaging in armchair punditry.
So take my suggestions with a grain of salt.

But I think the procedure I outlined should work well, no trouble with hearing a zerobeat?right off
if the si5351 25hz reference crystal and the 12mhz crystals are all within 50ppm or so.
If crystal tolerances exceed that, we may need to go to a two step procedure.

And should work with any known signal source that is within the capabilities of the receiver, 0-30mhz.
I'll play with the code if and and when I get my hands on a ubitx, see if I'm right about that.
I'd much prefer to zerobeat a time standard such as WWV than some random ham's 7050khz signal.
If not a time standard, then perhaps one of those nasty 41m broadcast stations that others tell us
is accurately on frequency. ?

It's not a disadvantage that all three clocks are locked to vcoa.
If we set the display to a known frequency then nudge vcoa around till the signal is correctly
received, the math is such that vcoa has exactly the frequency at which the vco is operating at.
And thus compensates for any error in the 25mhz reference crystal.
I'm assuming we call setfreq() for each of the three clocks each time we nudge vcoa.

One minor hack that might be fun to try on the Raduino: ?
Measure the temperature around the si5351 and the 25mhz crystal using a Nano analog pin
and a diode junction. ?Or perhaps a proper temperature sensor with i2c interface. ?
Adjust vcoa as a function of the temperature we sense using a piecewise linear fit stored in flash
that characterizes how the measured frequency of the 25mhz reference changes with temperature.
A cheap way to give us a very stable TCXO.

Jerry, KE7ER
?


On Thu, Dec 7, 2017 at 12:15 pm, Ashhar Farhan wrote:
Earlier, the calibration routine put out a 10 MHz signal out the antenna (by unbalancing the diode mixer and setting the first oscillator to 10 MHz). I chucked it because it assumed that everybody had a dummy load or a 10 MHz antenna.?
?
On the other hand, it is easier for a ham to call up someone and ask them to call CQ on a particular frequency. The way the present calibration works is like this. I call up ?friend to call CQ from his calibrated radio exactly at 7050 KHz. I set the dial to 7050 KHz, Then you switch on the calibration and tune until it goes dead zero beat.? If only life was that simple.?
?
First, the crystal filter has a steep skirt. We would ordinarily celebrate this. But in our case, that means, unless the signal is a 30 db over S9, you are not going to hear the zero beat, much less the swing to the other sideband.
?
Second issue with this is that as we recalibrate the VCO and reset the oscillators, the BFO too is corrected by an equal amount and the zero-beat will go away. To compensate for this, this is what I came up with, bear with me...
?
The VCO frequency is at 875 MHz. We generate any needed frequency by dividing the PLL by a fraction. So, to generate 1 Mhz, it is divided by 875. Now, suppose our reference that we are trying to align with is at 1 MHz, we need to nudge the 875 MHz VCO. If the VCO moves by 875 Hz, we can see the 1 MHz move by 1 Hz. To move the 1 MHz by 10 Hz at ?time, we have to move the VCO by 8750 Hz at a time. Our BFO is at 12 MHz, if we push the VCO up or down by 875 Hz, the 12 Mhz will be ?moved by 12 Hz. If we push the VCO around by 8750 Hz, the 12 Mhz BFO has to be corrected by 120 Hz. This is what the code does.?
?
Re: ubitx circuit, wiring, source code on github

 

¿ªÔÆÌåÓý

Jerry,

a similar situation will happen under "nromal conditions: the first mixer never is fully balanced resulting that receiving 12 MHz, tehre will be an attenuated 57 Mhz signal from the frist LO at the output of the first mixer besides the wanted? 45 MHz... we will have a big spur at 12 MHz antenna signal?!


Am 07.12.2017 um 20:44 schrieb Jerry Gaffke via Groups.Io:

To scan the 12mhz filter passband, I'm thinking we drive CW-KEY high to unbalance the first mixer,
freeze clk1 at 57mhz, then scan clk2 and clk0 around 45mhz and 12mhz respectively,
monitoring the resultant audio beat note with scope or AC voltage meter.

Since the first mixer is unbalanced, anything on clk2 will continue on through to the second mixer
where it mixes with the 57mhz clk1 to create something near 12mhz.?
If clk0 varies from 12.000mhz down to 11.990mhz while clk2 varies from 45.000mhz to 45.010mhz, we should hear a constant
1khz audio tone that varies in intensity according to the 12mhz crystal filter's response to the 57mhz-clk2 frequency that
is passing through it. ?This could be plotted on graph paper while reading the AC audio voltage and the frequency
of 57mhz-clk2 from the display,?

At any rate, nothing I am bringing up today should slow hfsigs down in building those rigs.
They will likely work fine as shipped, and all these minor adjustments will give the tinkerer's among us something to do.

Jerry, KE7ER


On Thu, Dec 7, 2017 at 10:09 am, Jerry Gaffke wrote:
An alternative would be to scan clk2 and clk0
through the crystal filter passband such that a constant frequency audio beat note is heard, and have the
user identify where the amplitude falls off at each edge of the 12mhz crystal filter passband.
Re: Any problem to have 2 sources powering the Raduino??

Gordon Gibby
 

¿ªÔÆÌåÓý

Thanks everyone for so much information. ?I may have missed stated, it was never my intention to provide +12 to the nano, only to the raduino. ? Adding the diode resistor and filtering is a next step. ?

Thanks again!

Sent from my iPhone

On Dec 7, 2017, at 15:18, RCBoatGuy via Groups.Io <ijnfan-HamRadio@...> wrote:

Jerry,

Please look in the lower left corner of the Nano schematic you linked to above.? That LM1117IMPX-5.0 device in the section labeled '+5V REG' is a +5V regulator that exists on the Nano's board.? Right beside it in the schematic is the SS1P3L Schottky diode for the USB power supply protection that you mentioned.? In addition, the Nano documentation itself clearly lists the on-board regulator as being supplied by the Vin 7-12V supply pin.

So, if you connect 12V to the Vin supply, you are shorting the Nano's regulator and the Raduino's regulator outputs together.? Neither device puts out a perfect 5.0V, so there is always some fighting going on.? Regulators typically have a +/- 5% variance over temperature, if properly filtered.? That's 4.75V to 5.25V, or a 0.5V (10%) swing with good filtering, more than enough to make the schottky diode conduct with its 0.1V - 0.4V forward voltage range.? And the filtering on both the Nano and Raduino boards is sub-optimal, at best, so the overshoot can exceed 5.25V and the undershoot can go below 4.75V.

Same is true for the USB supply, especially if you are using a cheap, unshielded USB cable -- it, too, can have significant noise, and the low forward voltage of the schottky diode means it doesn't take a lot to make it conduct.? When one supply is overshooting while another is undershooting, the problem is multiplied, and you can end up frying something.? The Nano's regulator is a tiny one, not meant to provide a lot of current.? Doesn't take much to overstress it.

The USB protection diode was an poor attempt to allow powering the USB and either the Nano's on board regulator or an external 5V regulator (never both!).? A proper attempt would have had a protection diode on the Nano's regulator output, too.?

BTW, I do think it's reasonable for an external supply to provide its own protection, so I don't fault them for not adding an on-board protection diode to the Nano's external 5V supply connection.

Gordon,

If you are using the Raduino's 5V regulator to power the Nano, I would recommend putting a switch in the line so you can fully power the Nano via USB when attached to a computer.? Either that, or add diode protection between the Raduino's regulator and the Nano to provide extra protection.? Above all, put the extra filtering on the Raduino 5V supply that has been suggested in this forum before.

I personally don't recommend connecting 12V to the Nano's Vin supply.? For one thing, 12V at the extreme range of what the Nano's regulator can handle.? Exceeding 12V will damage the Nano's regulator.? I think the power filtering on the Nano is inadequate, and it's not easy to add filtering to that tiny board given that the Raduino PCB connects the pin to the Raduino's 5V supply.? If you do add 12V to the Nano's Vin supply, I recommend the following:

1) That you put a diode in the 12V supply line as mentioned earlier

2) That you add a 9V regulator with decent filtering between the 12V supply and the Nano Vin pin to avoid overstressing the Nano's regulator.? This is especially true if you plan to run with a 13.8V supply any time in the future...

3) That you put a switch in the line to the Nano's Vin so you can disconnect the Vin supply when programming.?

4) That you disconnect the Raduino's 5V supply to the Nano when powering the Nano via the Vin supply.? Either that, or add the diode protection to the 5V supply, but disconnecting it is safer.

73,
Carl? K0MWC

?
Re: Any problem to have 2 sources powering the Raduino??

 

Oops, sorry, the 7-12V range is recommended, but the overall range is 6-20V.? So there may not be much point in adding the 9V regulator I suggested.?

73,
Carl? K0MWC
Re: Any problem to have 2 sources powering the Raduino??

 

Jerry,

Please look in the lower left corner of the Nano schematic you linked to above.? That LM1117IMPX-5.0 device in the section labeled '+5V REG' is a +5V regulator that exists on the Nano's board.? Right beside it in the schematic is the SS1P3L Schottky diode for the USB power supply protection that you mentioned.? In addition, the Nano documentation itself clearly lists the on-board regulator as being supplied by the Vin 7-12V supply pin.

So, if you connect 12V to the Vin supply, you are shorting the Nano's regulator and the Raduino's regulator outputs together.? Neither device puts out a perfect 5.0V, so there is always some fighting going on.? Regulators typically have a +/- 5% variance over temperature, if properly filtered.? That's 4.75V to 5.25V, or a 0.5V (10%) swing with good filtering, more than enough to make the schottky diode conduct with its 0.1V - 0.4V forward voltage range.? And the filtering on both the Nano and Raduino boards is sub-optimal, at best, so the overshoot can exceed 5.25V and the undershoot can go below 4.75V.

Same is true for the USB supply, especially if you are using a cheap, unshielded USB cable -- it, too, can have significant noise, and the low forward voltage of the schottky diode means it doesn't take a lot to make it conduct.? When one supply is overshooting while another is undershooting, the problem is multiplied, and you can end up frying something.? The Nano's regulator is a tiny one, not meant to provide a lot of current.? Doesn't take much to overstress it.

The USB protection diode was an poor attempt to allow powering the USB and either the Nano's on board regulator or an external 5V regulator (never both!).? A proper attempt would have had a protection diode on the Nano's regulator output, too.?

BTW, I do think it's reasonable for an external supply to provide its own protection, so I don't fault them for not adding an on-board protection diode to the Nano's external 5V supply connection.

Gordon,

If you are using the Raduino's 5V regulator to power the Nano, I would recommend putting a switch in the line so you can fully power the Nano via USB when attached to a computer.? Either that, or add diode protection between the Raduino's regulator and the Nano to provide extra protection.? Above all, put the extra filtering on the Raduino 5V supply that has been suggested in this forum before.

I personally don't recommend connecting 12V to the Nano's Vin supply.? For one thing, 12V at the extreme range of what the Nano's regulator can handle.? Exceeding 12V will damage the Nano's regulator.? I think the power filtering on the Nano is inadequate, and it's not easy to add filtering to that tiny board given that the Raduino PCB connects the pin to the Raduino's 5V supply.? If you do add 12V to the Nano's Vin supply, I recommend the following:

1) That you put a diode in the 12V supply line as mentioned earlier

2) That you add a 9V regulator with decent filtering between the 12V supply and the Nano Vin pin to avoid overstressing the Nano's regulator.? This is especially true if you plan to run with a 13.8V supply any time in the future...

3) That you put a switch in the line to the Nano's Vin so you can disconnect the Vin supply when programming.?

4) That you disconnect the Raduino's 5V supply to the Nano when powering the Nano via the Vin supply.? Either that, or add the diode protection to the 5V supply, but disconnecting it is safer.

73,
Carl? K0MWC

?
Re: ubitx circuit, wiring, source code on github

 

Jerry,?
Earlier, the calibration routine put out a 10 MHz signal out the antenna (by unbalancing the diode mixer and setting the first oscillator to 10 MHz). I chucked it because it assumed that everybody had a dummy load or a 10 MHz antenna.?

On the other hand, it is easier for a ham to call up someone and ask them to call CQ on a particular frequency. The way the present calibration works is like this. I call up ?friend to call CQ from his calibrated radio exactly at 7050 KHz. I set the dial to 7050 KHz, Then you switch on the calibration and tune until it goes dead zero beat.? If only life was that simple.?

First, the crystal filter has a steep skirt. We would ordinarily celebrate this. But in our case, that means, unless the signal is a 30 db over S9, you are not going to hear the zero beat, much less the swing to the other sideband.

Second issue with this is that as we recalibrate the VCO and reset the oscillators, the BFO too is corrected by an equal amount and the zero-beat will go away. To compensate for this, this is what I came up with, bear with me...

The VCO frequency is at 875 MHz. We generate any needed frequency by dividing the PLL by a fraction. So, to generate 1 Mhz, it is divided by 875. Now, suppose our reference that we are trying to align with is at 1 MHz, we need to nudge the 875 MHz VCO. If the VCO moves by 875 Hz, we can see the 1 MHz move by 1 Hz. To move the 1 MHz by 10 Hz at ?time, we have to move the VCO by 8750 Hz at a time. Our BFO is at 12 MHz, if we push the VCO up or down by 875 Hz, the 12 Mhz will be ?moved by 12 Hz. If we push the VCO around by 8750 Hz, the 12 Mhz BFO has to be corrected by 120 Hz. This is what the code does.?

- f

On Fri, Dec 8, 2017 at 1:14 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
To scan the 12mhz filter passband, I'm thinking we drive CW-KEY high to unbalance the first mixer,
freeze clk1 at 57mhz, then scan clk2 and clk0 around 45mhz and 12mhz respectively,
monitoring the resultant audio beat note with scope or AC voltage meter.

Since the first mixer is unbalanced, anything on clk2 will continue on through to the second mixer
where it mixes with the 57mhz clk1 to create something near 12mhz.?
If clk0 varies from 12.000mhz down to 11.990mhz while clk2 varies from 45.000mhz to 45.010mhz, we should hear a constant
1khz audio tone that varies in intensity according to the 12mhz crystal filter's response to the 57mhz-clk2 frequency that
is passing through it.? This could be plotted on graph paper while reading the AC audio voltage and the frequency
of 57mhz-clk2 from the display,?

At any rate, nothing I am bringing up today should slow hfsigs down in building those rigs.
They will likely work fine as shipped, and all these minor adjustments will give the tinkerer's among us something to do.

Jerry, KE7ER


On Thu, Dec 7, 2017 at 10:09 am, Jerry Gaffke wrote:
An alternative would be to scan clk2 and clk0
through the crystal filter passband such that a constant frequency audio beat note is heard, and have the
user identify where the amplitude falls off at each edge of the 12mhz crystal filter passband.


Re: Any problem to have 2 sources powering the Raduino??

Jack Purdum
 

Correct. I was just pointing that out in case there are any Nano experimenters out there. Also, while the spec says 6-20V on input using the regulator, it gets a little flaky when the voltage is below 7V and the chip gets pretty toasty at voltages above 15V.

Jack, W8TEE


From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: [email protected]
Sent: Thursday, December 7, 2017 2:50 PM
Subject: Re: [BITX20] Any problem to have 2 sources powering the Raduino??

You are correct, there is an LM1117 5v regulator between the Vin pin (Nano pin 15) and the Nano's 5v ral.
However, in my defense, the Raduino does not tie anything to pin 15, so this regulator is not used?
and should have no effect on what's going on with the Raduino.

Jerry KE7ER


On Thu, Dec 7, 2017 at 11:29 am, Jack Purdum wrote:
Jerry:
?
Are you sure about this:
?
First off, there is no 5v regulator on the Nano board.
?
The specs say it can be powered by:
????1) the USB port
????2) a 6-20V DC source (pin 30)
????3) a regulated 5V source (pin 27).
?
Jack, W8TEE
?
Re: Any problem to have 2 sources powering the Raduino??

 

You are correct, there is an LM1117 5v regulator between the Vin pin (Nano pin 15) and the Nano's 5v ral.
However, in my defense, the Raduino does not tie anything to pin 15, so this regulator is not used?
and should have no effect on what's going on with the Raduino.

Jerry KE7ER


On Thu, Dec 7, 2017 at 11:29 am, Jack Purdum wrote:
Jerry:
?
Are you sure about this:
?
First off, there is no 5v regulator on the Nano board.
?
The specs say it can be powered by:
????1) the USB port
????2) a 6-20V DC source (pin 30)
????3) a regulated 5V source (pin 27).
?
Jack, W8TEE
?
Re: ubitx circuit, wiring, source code on github

 

To scan the 12mhz filter passband, I'm thinking we drive CW-KEY high to unbalance the first mixer,
freeze clk1 at 57mhz, then scan clk2 and clk0 around 45mhz and 12mhz respectively,
monitoring the resultant audio beat note with scope or AC voltage meter.

Since the first mixer is unbalanced, anything on clk2 will continue on through to the second mixer
where it mixes with the 57mhz clk1 to create something near 12mhz.?
If clk0 varies from 12.000mhz down to 11.990mhz while clk2 varies from 45.000mhz to 45.010mhz, we should hear a constant
1khz audio tone that varies in intensity according to the 12mhz crystal filter's response to the 57mhz-clk2 frequency that
is passing through it. ?This could be plotted on graph paper while reading the AC audio voltage and the frequency
of 57mhz-clk2 from the display,?

At any rate, nothing I am bringing up today should slow hfsigs down in building those rigs.
They will likely work fine as shipped, and all these minor adjustments will give the tinkerer's among us something to do.

Jerry, KE7ER


On Thu, Dec 7, 2017 at 10:09 am, Jerry Gaffke wrote:
An alternative would be to scan clk2 and clk0
through the crystal filter passband such that a constant frequency audio beat note is heard, and have the
user identify where the amplitude falls off at each edge of the 12mhz crystal filter passband.
Re: Any problem to have 2 sources powering the Raduino??

Jack Purdum
 

Jerry:

Are you sure about this:

First off, there is no 5v regulator on the Nano board.

The specs say it can be powered by:
????1) the USB port
????2) a 6-20V DC source (pin 30)
????3) a regulated 5V source (pin 27).

Jack, W8TEE


From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: [email protected]
Sent: Thursday, December 7, 2017 2:15 PM
Subject: Re: [BITX20] Any problem to have 2 sources powering the Raduino??

I'm not so sure.

First off, there is no 5v regulator on the Nano board. ?
The Nano's 5v rail is wired directly to the Raduino's LM7805, no protection diode there.
The Nano's 5v rail can also be powered from the USB connector through a protection diode.
?The 3.3v Si5351 is operating off that same 5v rail by way of a 3.3v regulator hidden inside the USB chip on the Nano.

The protection diode on the Nano is an SS1P31 schottky diode, according to this schematic: ?
? ??
Here's the diode datasheet:
? ??
Forward voltage drop through the diode is somewhere between 0.1 and 0.4 volts, depending on how much current and how hot it is.
The LM7805 datasheet is here (one of many manufacturers), output voltage could be as low as 4.75v.:
? ??

Let's assume we have Bitx40 power on while the Nano has a USB cable in place.
If the host computer supplies a bit more than 5v to the USB port, or if the LM7805 output voltage is near the low end of their spec,
we may be powering the Nano plus the Si5351 from the USB port.
But that's no worse than the situation when we have the Raduino unplugged from the Bitx.
More typically, we'd get 5v from the LM7805 to power the Nano and Si5351, no current would be coming from the USB host.

If we power down the Bitx40 and Raj's diode is not in place, we might have 100ma of 5v going backwards
through the LM7805 into the Bitx40, and perhaps powering up the receiver. ?
But an extra 100ma through the protection diode probably won't fry anything.
However, if you somehow kick the Bitx40 into transmit mode, current could go much higher
and you may fry that protection diode. ?

So a good idea to add Raj's diode.

Some have seen Nano's blown when powering the Raduino from the Bitx while plugged into a USB host.
We don't really know for sure what's on the $2 Nano clones, and we don't know exactly what fried on those Nanos.

So I'd add Raj's diode, and also shut down power to the Bitx when plugging in a USB cable to the Nano.
Not exactly sure why you would need to power down the Bitx, but then we don't know exactly what happend
in those few cases where the Nano got fried. ?My guess is that Raj's diode would have prevented such trouble.

Jerry, KE7ER

?
On Thu, Dec 7, 2017 at 09:40 am, RCBoatGuy wrote:
When plugged into the Raduino board, the Nano is powered externally by a regulator on the Raduino board, which also has no protection diode.? So if you put 12V on the Nano Vin supply pin, you are shorting the outputs of the Nano's regulator to the Raduino's regulator, which in turn are connected via a diode to the USB supply.? The diode on the USB supply cannot provide adequate protection from the other supplies unless diodes exist on the other supplies, so when connecting the Nano via USB to a computer, the other supplies should be disconnected.
Re: Any problem to have 2 sources powering the Raduino??

 

I'm not so sure.

First off, there is no 5v regulator on the Nano board. ?
The Nano's 5v rail is wired directly to the Raduino's LM7805, no protection diode there.
The Nano's 5v rail can also be powered from the USB connector through a protection diode.
?The 3.3v Si5351 is operating off that same 5v rail by way of a 3.3v regulator hidden inside the USB chip on the Nano.

The protection diode on the Nano is an SS1P31 schottky diode, according to this schematic: ?
? ??
Here's the diode datasheet:
? ??
Forward voltage drop through the diode is somewhere between 0.1 and 0.4 volts, depending on how much current and how hot it is.
The LM7805 datasheet is here (one of many manufacturers), output voltage could be as low as 4.75v.:
? ??

Let's assume we have Bitx40 power on while the Nano has a USB cable in place.
If the host computer supplies a bit more than 5v to the USB port, or if the LM7805 output voltage is near the low end of their spec,
we may be powering the Nano plus the Si5351 from the USB port.
But that's no worse than the situation when we have the Raduino unplugged from the Bitx.
More typically, we'd get 5v from the LM7805 to power the Nano and Si5351, no current would be coming from the USB host.

If we power down the Bitx40 and Raj's diode is not in place, we might have 100ma of 5v going backwards
through the LM7805 into the Bitx40, and perhaps powering up the receiver. ?
But an extra 100ma through the protection diode probably won't fry anything.
However, if you somehow kick the Bitx40 into transmit mode, current could go much higher
and you may fry that protection diode. ?

So a good idea to add Raj's diode.

Some have seen Nano's blown when powering the Raduino from the Bitx while plugged into a USB host.
We don't really know for sure what's on the $2 Nano clones, and we don't know exactly what fried on those Nanos.

So I'd add Raj's diode, and also shut down power to the Bitx when plugging in a USB cable to the Nano.
Not exactly sure why you would need to power down the Bitx, but then we don't know exactly what happend
in those few cases where the Nano got fried. ?My guess is that Raj's diode would have prevented such trouble.

Jerry, KE7ER

?

On Thu, Dec 7, 2017 at 09:40 am, RCBoatGuy wrote:
When plugged into the Raduino board, the Nano is powered externally by a regulator on the Raduino board, which also has no protection diode.? So if you put 12V on the Nano Vin supply pin, you are shorting the outputs of the Nano's regulator to the Raduino's regulator, which in turn are connected via a diode to the USB supply.? The diode on the USB supply cannot provide adequate protection from the other supplies unless diodes exist on the other supplies, so when connecting the Nano via USB to a computer, the other supplies should be disconnected.
Re: ubitx circuit, wiring, source code on github

 

Looking over the sketch, not quite sure what all is going on yet with si5351_set_calibration()
Here's what I would expect to see:

Place the BFO (clk0) somewhere near the middle of the crystal filter passband so we can hear a zero beat.
An uncalibrated BFO frequency of 11997000 hz should be close enough.

Place clk1 (the local oscillator into the second mixer) at 45mhz + 12mhz = 57mhz ?(the 45mhz filter is fairly wide, should not be critical)

Have the user tune clk2 (the VFO into the first mixer) till the display shows the exact frequency for a signal of known frequency.
This signal could be from a calibrated signal generator or an AM station such as WWV, or a CW transmitter with a brick on the key.
The displayed frequency should be exactly ? sig = clk2-(clk1-clk0),
where clk0, clk1, clk2 are the value provided in the second parameter to si5351bx_setfreq(clknum, fout)
Given a signal frequency, we can compute the VFO frequency as ? clk2 = sig+(clk1-clk0).

For example, assume we are tuned to WWV at 15mhz, with clk0=11.997mhz, and clk1=57mhz
Then clk2 (the VFO) should have a value of ? ?clk2 = sig+(clk1-clk0) = 15mhz+(57mhz-11.997mhz) = 60.003mhz
when the display reads 15000000 hz.

Ask the user to turn the tuning knob until zerobeat is achieved, the tuning knob controls the value
of the calibration factor si5351bx_vcoa
The granularity with which si5351bx_vcoa can be varied should be down in the low single digits.
This accuracy will be very useful in some digital modes. ?Perhaps use Don Cantrell's shuttle tuning
scheme, with increments/decrements of 1 for si5351bx_vcoa near the middle of the tuning range. ?
The display should somehow indicate how far si5351bx_vcoa is from its nominal value of 875mhz.

For each change in the value of si5351bx_vcoa, do the following three function calls:
? ? si5351bx_setfreq(0, FREQclk0)
? ? si5351bx_setfreq(1, FREQclk1)
? ? si5351bx_setfreq(2, FREQclk2)

Note that the values for those three frequencies do not change.
In our example, they remain fixed at 11.997mhz, 57mhz, and 63.003mhz respectively.
However, as the calibration value si5351bx_vcoa changes between calls,
the frequency emitted by the three clock outputs will change proportional to that calibration constant.

When the user hears zerobeat, they press a button to save that value of si5351bx_vcoa
At this point, the Si5351's 25mhz reference oscillator is exactly calibrated, and any frequency we
program into clk0, clk1, or clk2 ?should be correct to within a fraction of a hz.
?
Once the si5351 is calibrated using the above procedure, then the user is asked to position the BFO
for the upper and lower sideband settings. ?One way would be to have an incoming SSB signal of
known quality, and then set the BFO for best audio clarity. ?An alternative would be to scan clk2 and clk0
through the crystal filter passband such that a constant frequency audio beat note is heard, and have the
user identify where the amplitude falls off at each edge of the 12mhz crystal filter passband.?

Jerry, KE7ER



On Wed, Dec 6, 2017 at 09:02 pm, Ashhar Farhan wrote:
i have uploaded the sketch for the ubitx, wiring diagrams and the circuit on github. ou can see it on?
?
Re: Any problem to have 2 sources powering the Raduino??

Gordon Gibby
 

¿ªÔÆÌåÓý

Thanks Carl --- would it also make sense just to cut the red (+5V) line in whatever cable you are going to use to control or program a nano while in use?? ?In the application I foresee, the Raduino would be powered by a 7-12V supply, but computer control of the radio might be coming in over the micro-usb port of the nano (CAT emulation).


(I'm leaning toward having the power to the raduino board be constant and unchanging, because the application requires the radio to be usable with or without computer control, and tThe users of this installed system might be confused by the need to turn this or that power supply off.....)


Thanks for your thoughts,


gordon




From: [email protected] <[email protected]> on behalf of RCBoatGuy via Groups.Io <ijnfan-HamRadio@...>
Sent: Thursday, December 7, 2017 12:40 PM
To: [email protected]
Subject: Re: [BITX20] Any problem to have 2 sources powering the Raduino??
?
Small boards like the Nano are not designed to give every supply source adequate protection in order to a) keep costs down and b) keep the PCB small.? So sometimes you let the smoke out if you are not very careful with the supplies.

Thus, do to its small nature, the Nano is designed to use **one and only one** of 3 possible power sources.? Only 1 power source is actually protected by a diode, so you are only supposed to connect one supply source at a time.?

When plugged into the Raduino board, the Nano is powered externally by a regulator on the Raduino board, which also has no protection diode.? So if you put 12V on the Nano Vin supply pin, you are shorting the outputs of the Nano's regulator to the Raduino's regulator, which in turn are connected via a diode to the USB supply.? The diode on the USB supply cannot provide adequate protection from the other supplies unless diodes exist on the other supplies, so when connecting the Nano via USB to a computer, the other supplies should be disconnected.

So, if you connect 12V to the Nano Vin supply pin, you must first disconnect the Raduino's 5V supply connection to the Nano.? Even then, you should still disconnect the 12V supply when programming the Nano via the USB port (just add a switch to the 12V supply line going to the Nano).

73
Carl? K0MWC
Re: Any problem to have 2 sources powering the Raduino??

 

Small boards like the Nano are not designed to give every supply source adequate protection in order to a) keep costs down and b) keep the PCB small.? So sometimes you let the smoke out if you are not very careful with the supplies.

Thus, do to its small nature, the Nano is designed to use **one and only one** of 3 possible power sources.? Only 1 power source is actually protected by a diode, so you are only supposed to connect one supply source at a time.?

When plugged into the Raduino board, the Nano is powered externally by a regulator on the Raduino board, which also has no protection diode.? So if you put 12V on the Nano Vin supply pin, you are shorting the outputs of the Nano's regulator to the Raduino's regulator, which in turn are connected via a diode to the USB supply.? The diode on the USB supply cannot provide adequate protection from the other supplies unless diodes exist on the other supplies, so when connecting the Nano via USB to a computer, the other supplies should be disconnected.

So, if you connect 12V to the Nano Vin supply pin, you must first disconnect the Raduino's 5V supply connection to the Nano.? Even then, you should still disconnect the 12V supply when programming the Nano via the USB port (just add a switch to the 12V supply line going to the Nano).

73
Carl? K0MWC
Re: Any problem to have 2 sources powering the Raduino??

Gordon Gibby
 

¿ªÔÆÌåÓý

?Jerry -- thank you SO MUCH for taking the time to put that information together!? ?Much appreciated.? ?The series diode and low pass filtering of the power sound like great ideas.? ?


THANKS!!!!!!!!!!!!!!


Gordon


From: [email protected] <[email protected]> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Thursday, December 7, 2017 10:57 AM
To: [email protected]
Subject: Re: [BITX20] Any problem to have 2 sources powering the Raduino??
?
This has been hotly debated in the past:
? ??
? ??
? ??

That first post above by Raj notes that the 5v from your USB host can back
through the LM7805 and push 5v back into the main Bitx40 board. ?
The Bitx40 is sucking enough current that it might blow a diode on the Nano.
Solution to this is to add a 1n400x (such as a 1n4007) in series with the 12v lead
from Bitx40 over into the Raduino.

While you are at it, would be good to also?add a series 1/2 watt resistor of 50 ohms or less.
and a 10uF cap or greater across 12v and ground at the Raduino.
This will keep power supply noise such as tuning clicks from getting back into the radio.
The voltage drop across the 50 ohm resistor keeps the Raduino's LM7805 from getting hot.
So looks like this:
Bitx12vPwr------diode->|-----50ohms-----------Raduino12vPwrPin-----10uF------RaduinoGnd
The voltage at that Raduino12vPwrPin should be 7v or greater, if that is not the case
then the Raduino is taking more current from the power supply than it should and thus
the voltage drop across the resistor is getting too large.

Most people seem to be having good luck with leaving the Bitx40 power on
when plugging a USB connector into the Nano. ?But several posts in the threads
above say that doing so fried their Nano. ?Perhaps not all Nano clones are
created equal. ?Could well be minor difference between the $22 Nano from the
Arduino Store and some of the $2 Ebay clones. ??

I would recommend adding Raj's diode, and also cut power to the Bitx40
whenever plugging in the USB cable.

Jerry, KE7ER


On Thu, Dec 7, 2017 at 05:59 am, Gordon Gibby wrote:
All of the above suggests it might be safe to have power arriving from both directions --- if indeed there is a separation diode as shown in the Arduino Nano Rev 3.2 schematic.....
Re: Shielding plastic boxes

 

Hi all,

I have a question, that may be an answer also.

When I put up my Hexbeam antenna, I used square matal pipes for the support allbeen zinc hot threated. On some iron parts I used a zinc cold spray to protect these from rusting.
I do not have anymore spray so I cannot try and test if it is conductive or not. If it is conductive it could give a valid emc rfi screening, certainly not like a metal one.
Anyone tried this solution?

73

Gian
I7SWX
81781 - 81800 of 117000