Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
My zBitx arrived today. I can confirm that when working from batteries, it produces those modulation (?) components.  
73, Wojtek SP5DAA? ?r., 16 kwi 2025, 17:36 u?ytkownik Joerg DB2OO via <db2oo.ju= [email protected]> napisa?:
To be on the safe side, I tested it with a lab supply as well as with 18650 batteries:
Same result, the +/- 2.x MHz spurs are there with both types of power supplies!
?
I think the spurs are originating in the SI5351/MS5351, which has to deliver much more power than in the sBitx, which has low oscillator power demand, due to buffer amplifier for the 40MHz and high impedance input of the KISS-Mixer.
?
The only band, where I did not see them is 80m, where the output seems to be clean.?
?
On Wed, Apr 16, 2025 at 10:00 AM, < Vu3vwr@...> wrote:
Joerg,
Are you running the tests with batteries or are you using an SMPS to power the radio during the test? 2MHz is a common switching frequency and as Wojtek suggests, the issue maybe the PS.
?
I have raised this with Farhan and will wait for him to chime in on this after he has a look.?
?
73,
Ragav
?
--
73, Joerg - DB2OO
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Jeorg,? Please describe your set-up and monitoring cabling, antenna etc,l BSEE, ? AASEET, ? FCC Lic.# PG-18-19178, ? KG9H Electronic Instrument Associates?- Central, Inc. ...since 1971 w:???d/l our linecard at???
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On Apr 16, 2025, at 11:36?AM, Joerg DB2OO via groups.io <db2oo.ju@...> wrote:
? To be on the safe side, I tested it with a lab supply as well as with 18650 batteries:
Same result, the +/- 2.x MHz spurs are there with both types of power supplies!
?
I think the spurs are originating in the SI5351/MS5351, which has to deliver much more power than in the sBitx, which has low oscillator power demand, due to buffer amplifier for the 40MHz and high impedance input of the KISS-Mixer.
?
The only band, where I did not see them is 80m, where the output seems to be clean.?
?
On Wed, Apr 16, 2025 at 10:00 AM, <Vu3vwr@...> wrote:
Joerg,
Are you running the tests with batteries or are you using an SMPS to power the radio during the test? 2MHz is a common switching frequency and as Wojtek suggests, the issue maybe the PS.
?
I have raised this with Farhan and will wait for him to chime in on this after he has a look.?
?
73,
Ragav
?
--
73, Joerg - DB2OO
-- ?
?
?
de KG9H
Life member, ARRL
|
Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
I crossed checked with two different models of tinySA, and also compared against two other QRP transmitters using the same 50 dB attenuation chain at similar power levels. ?Only my zbitx showed the +-2.5 MHz sideband spurs. ?Other rigs did not.
?
Also, after I disconnected and turned of the tinySA, I could still hear the spurs using a separate receiver placed near enough to a 50 Ohm dummy load the zbitx was transmitting into (but not close enough to overload the receiver).
?
So, if others don't see these spurs, maybe I received a bad unit?
?
73, Ron, n6ywu
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
To be on the safe side, I tested it with a lab supply as well as with 18650 batteries:
Same result, the +/- 2.x MHz spurs are there with both types of power supplies!
?
I think the spurs are originating in the SI5351/MS5351, which has to deliver much more power than in the sBitx, which has low oscillator power demand, due to buffer amplifier for the 40MHz and high impedance input of the KISS-Mixer.
?
The only band, where I did not see them is 80m, where the output seems to be clean.?
?
On Wed, Apr 16, 2025 at 10:00 AM, <Vu3vwr@...> wrote:
Joerg,
Are you running the tests with batteries or are you using an SMPS to power the radio during the test? 2MHz is a common switching frequency and as Wojtek suggests, the issue maybe the PS.
?
I have raised this with Farhan and will wait for him to chime in on this after he has a look.?
?
73,
Ragav
?
--
73, Joerg - DB2OO
|
Re: zBitx touchsreen issue
Power up the unit while pressing the screen with the stylus. it will bring up a calibration menu.?
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
If the problem is related to the change of power supply voltage due to periodically changing current consumption, the problem may persist with battery supply. They have non-zero internal resistance.
73, Wojtek SP5DAA? ?r., 16 kwi 2025, 14:00 u?ytkownik Ron, N6YWU via <ron.nicholson= [email protected]> napisa?:
I tested my unit with two different sets of batteries, and saw the +-2 MHz spurs. So it's not external SMPS noise.
?
The spurs were there when trying to FT8, CW, and 2Tone modes, They only vanished when trying SSB with no mic, thus 0 output.
?
Ron, n6ywu
?
?
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Ashhar,
Thanks for the information.
My business is Electromagnetic Compatibility for the past 40 years or so.
I have been following along on all the posts.
So many folks take their (fill in the blank) shack in the box, and make assumptions on spurs, etc. of a transmitter, without any reference to the measurement set-up or analyzer. ?
You cannot make any assumption about a transmitter with a shack in the box, guys.
? ? ?Frank Krozel ? ? ? ? ? ?KG9H Life Member, ARRL ? ? (630) 924-1600 kg9hfrank@...
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On Apr 16, 2025, at 10:41?AM, Ashhar Farhan via groups.io <farhanbox@...> wrote:
You could probe the input to the 3.3v regulator. However, this is a little more complicated than what it appears to be.
First, I spent weeks measuring the spurs. They are all below -43dbc except on 21 mhz. To quote a politician: "those are my alternate facts".
But, we must first be a little careful in trusting the tinysa. About 10 years ago, I built a spectrum analyser. The amount of shielding it needed was insanely high. See?. The spectrum analyzer needs to be carefully shielded at all stages to be useful, esp with a transmitter testng. The signal from the antenna terminal is reduced at least 60 dB before being applied to the spectrum analyzer. On the other hand, there are many other ways that the RFI can leak from the radio into the spectrum analyzer at any stage and produce these heterodyne beats. The TinySA is a single PCB with mixed signals without any shielding.?
The zbitx is a superhet radio with a number of oscillators apart from just the Si5351. There is a 12 MHz crystal on the WM8731, a TCXO at 25 MHz, many spurs coming out of the RPI, the display and the Pico. However, the diode mixer of the zbitx was chosen as a doubly balanced mixer that has far fewer spurs than the Kiss Mixer of the sbitx. This is borne by direct measurements?as well. The uBitx too uses exactly the same front end (of diode mixers driven by an IF amplifier) in transmit, it has acceptable spurious emissions.
For a proper testing, you need a very well shielded or a professional quality instrument. Both my spectrum analyzers, the specan and the Rigol DSA-815 are those. My tests were done on both.? I have also noted a correlation?between the bias current and the spurs. Here are my settings on the on the test bench with the DSA-815:
The output of the TX is connected to a dummy load made from 20 x 2 W, 1K carbon resistors. A sniffer consisting of a 100K in series with a 50 ohms is used to tap the input into the DSA-815.? The Spectrum Analyzer is set to 30 KHz resolution bandwidth, span of 70 MH, the zbitx mode is set to CW, straight key. These are the recommendations of the ARRL's testing lab.??
I will repeat these tests and post the pictures tomorrow. GM Gordon,?
I still believe it could be a power issue - the 3.3v regulator does not appear to be properly filtered per the manufacturer Datasheet. The other possibility is that the output of the 5351 is loaded too much under transmit conditions.?The effect could even be combined.?One or both of these problems could occur only when the circuit is loaded (transmitting).? I'd measure the 3.3V regulator output under both receive and transmit conditions. If that varies more than a little bit, there may be an issue on the regulator side. Substituting the 5351 with a signal generator could give an indication if the 5351 might be involved.?
I suspect a combination effect.?
Lee KX4TT
On Wednesday, April 16, 2025 at 08:27:27 AM EDT, Gordon Gibby KX4Z via ??<docvacuumtubes= [email protected]> wrote:
Well that tells us even more.. Not due to the power supply. Unlikely to be produced BEFORE the crystal filter (it would screen it out) Has to be coming in AFTER the filter Dependent on the existence of some desired signal level for existence.? Not just being picked up "as is" from another wire.? ? ? Hence, possibly an IMD product with some other signal in the box.? ?
Gordon KX4Z
-- ?
?
?
de KG9H
Life member, ARRL
|
zBitx touchscreen no longer aligned.
?
When I press the macro key "F4", the terminal reports that I pressed "F1".
?
rev 1.06 / 3.052.
?
Any help appreciated.
?
Thanks,
AC4OW, Sam Hanie
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
You could probe the input to the 3.3v regulator. However, this is a little more complicated than what it appears to be.
First, I spent weeks measuring the spurs. They are all below -43dbc except on 21 mhz. To quote a politician: "those are my alternate facts".
But, we must first be a little careful in trusting the tinysa. About 10 years ago, I built a spectrum analyser. The amount of shielding it needed was insanely high. See?. The spectrum analyzer needs to be carefully shielded at all stages to be useful, esp with a transmitter testng. The signal from the antenna terminal is reduced at least 60 dB before being applied to the spectrum analyzer. On the other hand, there are many other ways that the RFI can leak from the radio into the spectrum analyzer at any stage and produce these heterodyne beats. The TinySA is a single PCB with mixed signals without any shielding.?
The zbitx is a superhet radio with a number of oscillators apart from just the Si5351. There is a 12 MHz crystal on the WM8731, a TCXO at 25 MHz, many spurs coming out of the RPI, the display and the Pico. However, the diode mixer of the zbitx was chosen as a doubly balanced mixer that has far fewer spurs than the Kiss Mixer of the sbitx. This is borne by direct measurements?as well. The uBitx too uses exactly the same front end (of diode mixers driven by an IF amplifier) in transmit, it has acceptable spurious emissions.
For a proper testing, you need a very well shielded or a professional quality instrument. Both my spectrum analyzers, the specan and the Rigol DSA-815 are those. My tests were done on both.? I have also noted a correlation?between the bias current and the spurs. Here are my settings on the on the test bench with the DSA-815:
The output of the TX is connected to a dummy load made from 20 x 2 W, 1K carbon resistors. A sniffer consisting of a 100K in series with a 50 ohms is used to tap the input into the DSA-815.? The Spectrum Analyzer is set to 30 KHz resolution bandwidth, span of 70 MH, the zbitx mode is set to CW, straight key. These are the recommendations of the ARRL's testing lab.??
I will repeat these tests and post the pictures tomorrow.
GM Gordon,?
I still believe it could be a power issue - the 3.3v regulator does not appear to be properly filtered per the manufacturer Datasheet. The other possibility is that the output of the 5351 is loaded too much under transmit conditions. The effect could even be combined.?One or both of these problems could occur only when the circuit is loaded (transmitting).? I'd measure the 3.3V regulator output under both receive and transmit conditions. If that varies more than a little bit, there may be an issue on the regulator side. Substituting the 5351 with a signal generator could give an indication if the 5351 might be involved.?
I suspect a combination effect.?
Lee KX4TT
On Wednesday, April 16, 2025 at 08:27:27 AM EDT, Gordon Gibby KX4Z via <docvacuumtubes= [email protected]> wrote:
Well that tells us even more.. Not due to the power supply. Unlikely to be produced BEFORE the crystal filter (it would screen it out) Has to be coming in AFTER the filter Dependent on the existence of some desired signal level for existence.? Not just being picked up "as is" from another wire.? ? ? Hence, possibly an IMD product with some other signal in the box.? ?
Gordon KX4Z
|
Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
GM Gordon,?
I still believe it could be a power issue - the 3.3v regulator does not appear to be properly filtered per the manufacturer Datasheet. The other possibility is that the output of the 5351 is loaded too much under transmit conditions. The effect could even be combined.?One or both of these problems could occur only when the circuit is loaded (transmitting).? I'd measure the 3.3V regulator output under both receive and transmit conditions. If that varies more than a little bit, there may be an issue on the regulator side. Substituting the 5351 with a signal generator could give an indication if the 5351 might be involved.?
I suspect a combination effect.?
Lee KX4TT
On Wednesday, April 16, 2025 at 08:27:27 AM EDT, Gordon Gibby KX4Z via groups.io <docvacuumtubes@...> wrote:
Well that tells us even more.. Not due to the power supply. Unlikely to be produced BEFORE the crystal filter (it would screen it out) Has to be coming in AFTER the filter Dependent on the existence of some desired signal level for existence.? Not just being picked up "as is" from another wire.? ? ? Hence, possibly an IMD product with some other signal in the box.? ?
Gordon KX4Z
|
Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Well that tells us even more.. Not due to the power supply. Unlikely to be produced BEFORE the crystal filter (it would screen it out) Has to be coming in AFTER the filter Dependent on the existence of some desired signal level for existence.? Not just being picked up "as is" from another wire.? ? ? Hence, possibly an IMD product with some other signal in the box.? ?
Gordon KX4Z
On Wed, Apr 16, 2025 at 8:00?AM Ron, N6YWU via <ron.nicholson= [email protected]> wrote: I tested my unit with two different sets of batteries, and saw the +-2 MHz spurs. So it's not external SMPS noise.
?
The spurs were there when trying to FT8, CW, and 2Tone modes, They only vanished when trying SSB with no mic, thus 0 output.
?
Ron, n6ywu
?
?
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
I tested my unit with two different sets of batteries, and saw the +-2 MHz spurs. So it's not external SMPS noise.
?
The spurs were there when trying to FT8, CW, and 2Tone modes, They only vanished when trying SSB with no mic, thus 0 output.
?
Ron, n6ywu
?
?
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Re: Where is the line at for ZbitX's that are shipping.
Quickly is all I can say,
My Order (#3595) was place UK 1st April 2025 @ 06:24 GMT
Shipment collected Hyderabad -12:00 UTC 14th April 2025
Shipment expected by 23:59 on 17th April 2025
Actual Arrival 10:03 GMT 16th 2025 - Central Hertfordshire UK?
This is a very respectful turnaround (15 Days all in) on my order.
Will decant and process after work this evening.
73
BigJonn G8DVB
?
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Re: #zBitx timezone issue
#zbitx
Also look at the dot profile file in the /home/pi directory and /etc/profile? file and make sure that the "TZ =" command is commented out if is in the file.
Leo, AI5II
ALL of the stuff below PLUS a reboot too...!!
es vy 73 de "baab" w9ya On Tue, Apr 15, 2025 at 8:17?PM Leo Aniol, AI5II via <leomaniolone= [email protected]> wrote: Do a sudo dpkg-reconfigure tzdata.
Leo , AI5II
i cannot seem to get the zBitx to have the correct time
?
I run raspi-config and change the TZ to Chicago but the date command still says MST.
?
pi@sbitx:~ $ sudo raspi-config
?
Current default time zone: 'America/Chicago'
Local time is now:? ? ? Tue Apr 15 19:38:14 CDT 2025.
Universal Time is now:? Wed Apr 16 00:38:14 UTC 2025.
?
pi@sbitx:~ $ date?
Tue 15 Apr 2025 05:38:31 PM MST
pi@sbitx:~ $?
?
?
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Important question!? ?If the power supply turned out to be the culprit, then would be much easier to avoid.? ? With the sBitx I found that any screwup of the analog?+12 line caused huge problems.....? more bypassing helped greatly there.? ?Perhaps same here? Gordon KX4Z
For me, it is an important lesson. I always avoided poor-quality power supplies, as they impaired my RX noise. However, that issue shows that a PS with a high-frequency ripple on the output may lead to parasitic AM modulation of my output signal and make me violate my license conditions due to transmitting outside the amateur band...
73,
Wojtek SP5DAA
Joerg,
Are you running the tests with batteries or are you using an SMPS to power the radio during the test? 2MHz is a common switching frequency and as Wojtek suggests, the issue maybe the PS.
?
I have raised this with Farhan and will wait for him to chime in on this after he has a look.?
?
73,
Ragav
--
Wojciech M. Zabo?otny
My GPG/PGP keys:
standard: 8192R/7E17F00A (B53C 1F09 BEA9 ED46 51B6 ?2C2E 4344 F292 7E17 F00A)
confidential: 16384R/1FEDB03C (3412 2330 E225 D57D 70C3 ?2340 B294 9408 1FED B03C)
|
Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
For me, it is an important lesson. I always avoided poor-quality power supplies, as they impaired my RX noise. However, that issue shows that a PS with a high-frequency ripple on the output may lead to parasitic AM modulation of my output signal and make me violate my license conditions due to transmitting outside the amateur band...
73,
Wojtek SP5DAA
Joerg,
Are you running the tests with batteries or are you using an SMPS to power the radio during the test? 2MHz is a common switching frequency and as Wojtek suggests, the issue maybe the PS.
?
I have raised this with Farhan and will wait for him to chime in on this after he has a look.?
?
73,
Ragav
-- Wojciech M. Zabo?otny
My GPG/PGP keys:
standard: 8192R/7E17F00A (B53C 1F09 BEA9 ED46 51B6 ?2C2E 4344 F292 7E17 F00A)
confidential: 16384R/1FEDB03C (3412 2330 E225 D57D 70C3 ?2340 B294 9408 1FED B03C)
|
Re: Where is the line at for ZbitX's that are shipping.
Greetings Everyone:
?
My order, #3634, shipped early yesterday morning (UTC-4), and is scheduled for delivery on Thursday 4/17/25. ?I ordered the batteries as well from Amazon, and are scheduled to be delivered on Thursday as well.
?
They are turning out the zBITX very fast. ?At least it seems that way to me.
?
73 de Darrell KT4WX
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Yes, Nigel. I will be updating the manual soon.?
73,
Ragav
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Will the instruction manual get updated soon to include information such as logging export, to save repeat questions on the forum, and users having to trawl the forum for answers?
73 de Nigel Evans
Callsign: M0NDE QTH: Rhyl Locator: IO82
Jeff,
When you are connected to an external HDMI display, you can use the export function on the logger to save the log as an ADIF file.?
Please have a look at for info on how to export the log as ADIF file.
?
73,
Ragav
?
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Jeff,
When you are connected to an external HDMI display, you can use the export function on the logger to save the log as an ADIF file.?
Please have a look at for info on how to export the log as ADIF file.
?
73,
Ragav
?
|
Sam Hanie
Lee
Darrell Davis KT4WX
Nigel Evans M0NDE