Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
On Thu, Apr 17, 2025 at 06:34 AM, Joerg DB2OO wrote:
As a final proof, that the TinySA results in this specific scenario (we are NOT measuring IMD of the PA, but spurs) are trustworthy, I connected my Hermes-Lite-2 to exactly the same attenuator chain (20dB Weinschel 0-3GHz power attenuator, 30dB SMA attenuator) and measured the output spectrum on 18.1MHz:
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Wow!? I have certainly learned a LOT about the TinySA (I think ron meant this when he wrote "nanoVNA") in this discussion!? ?Joerg has apparently proven conclusively on his unit that there is an issue.? ? I had similar problems early on with one of my sBitx's which were subsequently resolved -- after a LOT of effort!? ?Hans is giving us lots of engineering advice here.? ? Need to have some measurement of the "distribution" of these difficulties with production units (could range from miniscule to "most" -- and so far no one knows that percentage) -- and gotta FIX IT as well.? ? That Ashhar's unit does NOT have the problem is certainlly encouraging!!? ??
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Might want to come up with a simple test that people can do with a general purpose receiver, or using WebSDR receivers, to make a general estimate of whether a given unit has the difficulty.? ? The existence of the 2MHz spur might make an easy way to do this:? ?a simple low-pass circuit and then a diode for a detector and measure the level and bingo! you know whether your unit has the issue.? ? The low pass filter would need to be sufficent to separate the -30 to -40 dBc 2MHz signal from the carrier.? ? So it might need to have several cascaded sections, but not difficult to build.? ? ? ? However, many users will have a second receiver or some sort and even using an S-meter they can get a "general" idea knowing where to look and comparing the s-meter readings using some simple secondary antenna.? ?None of this will be "accurate" but it will help the installed base of users figure out their unit without needing a spectrum analyzer.? ? ?
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Meanwhile, I'm down in the weeds of the source code of hamlib's rigcontrol to try and get it to properly control an 820h's two vfo's.? ?The writers clearly left hints that they didn't understand the radio architecture and I have been unable to get it to properly set the two halfs of the radio for satellite work -- yet I can easily do it using RIGCTL from the keyboard, accessing MainA and SubA.? ? So I'm going to try and "adjust" their code so I can get their system to work the radio properly.? ?Thanks to an Austrailian ham I learned how to compile hamlib!
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Gordon KX4Z
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Good question. ?I do not have a test & measurement lab; nor am I a qualified test & measurement technician.? I know what those are, having worked up at HP Labs in the distant past, with access to building-sized anechoic test chambers for RF isolation. ?However I prefer the hobby projects and radios on my bench to have enough statistical margins so as not to suggest that they are significantly outside the regulatory limits, via multiple independent quick and dirty tests, that do not require a proper measurement lab.
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Note that a nanoVNA isn¡¯t the only way to detect large spur signals. ?As a cross check, after noting the frequencies of the spurs with the nanoVNA, I shut off and disconnected the nanoVNA, and then verified the that those spurs were still present and within the non-overloaded dynamic range of an air-gapped Hermes Lite 2. ?There should have been over 7 S-units of difference to meet regulatory requirements, and on multiple bands, the differences in S meter readings were not even close enough to be a statistical error. ?Thus, IMHO, there is a reasonable likelihood that the spurs are real in my sample of one. ?Confirmation by several others using slightly different measurement methods increases that likelihood, even without more expensive lab grade test equipment in anechoic chambers.
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So my current hypothesis is that there are manufacturing variations in components, and Ashhar is testing a sample on the plus side of the bell curve. ?This perhaps suggests that either HFSignals got a bad batch of components that need to be replaced, and/or that a moderate redesign with higher manufacturing margins is in order. ?More testing by engineers with better labs will be required to confirm either of these hypothesis.
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The zbitx is a very interesting radio architecture, and I hope to eventually have one that I can connect to an antenna with the confidence that I am operating within the privileges of my amateur radio license.
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73, Ron, N6YWU.
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Re: Alternate power source for zbitx
We should be looking at LiFePo4 packs:
Mike N2MS
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On 04/17/2025 9:44 AM EDT Giuseppe Stancanelli - IU0OYC via groups.io <g.stanca@...> wrote:
Hi
I have some LiPo power packs, 2S, with various power (capacity) ratings. Some are rated for a discharge rate over 20-30 times the rated nominal capacity.
I have no economic reason or interest in suggesting this, but i think that can be a smart solution to power the zbitx.
Only for example, the following battery as 7.4 nominal voltage, 3600 mA capacity, size65 x 50 x 28mm and weight 165 g. Price under 13 €
Another interesting option is the hardcase batteries: this one has a capacity of 3000 mA, size 93 x 47 x 19 mm, weight 143g, and price a little more than 11€.
73 from Italy
Giuseppe IU0OYC
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Re: Alternate power source for zbitx
They should work great, I'm using these, ? and they run the zBitx for a longer time compared to the 2 cell pack that failed after 2.5 hours of RXing only.
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Joel
N6ALT
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Alternate power source for zbitx
Hi
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I have some LiPo power packs, 2S, with various power (capacity) ratings. Some are rated for a discharge rate over 20-30 times the rated nominal capacity.
I have no economic reason or interest in suggesting this, but i think that can be a smart solution to power the zbitx.
Only for example, the following battery as 7.4 nominal voltage, 3600 mA capacity, size 65 x 50 x 28mm and weight 165 g. Price under 13 €
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Another interesting option is the hardcase batteries: this one has a capacity of 3000 mA, size 93 x 47 x 19 mm, weight 143g, and price a little more than 11€.
73 from Italy
Giuseppe IU0OYC
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
As a final proof, that the TinySA results in this specific scenario (we are NOT measuring IMD of the PA, but spurs) are trustworthy, I connected my Hermes-Lite-2 to exactly the same attenuator chain (20dB Weinschel 0-3GHz power attenuator, 30dB SMA attenuator) and measured the output spectrum on 18.1MHz:
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All spurs disappear in the noise.
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For comparison the same measurement on 18.1MHz with the zBitx:
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I think the difference is obvious and proves, that the problem is with the zBitx and not the TinySA.
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BTW: To make it very clear: I like the sBitx and zBitx concepts VERY much. For me they are offering unique features, that you don't find in any other transceivers at least not at this price point.
My objective is just to make sure, that they fulfill the legal specifications, so that I can use and enjoy my zBitx.?
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73, Joerg - DB2OO
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Evan,
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On Wed, Apr 16, 2025 at 11:34 PM, Evan Hand wrote:
Wojtek,
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From the TinySA Ultra wiki:
- For best measurements keep input power below -25dBm
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I always ensure that the peak displayed is below -25dBm.? With either my Basic or Ultra, I get different results if I go above that value.
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My setup uses a 40dB 25¡ªor 100-watt attenuator followed by a 2-watt-rated step attenuator to dial in the best signal level for the measurement.
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73
Evan
AC9TU
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the -25dBm input limit for best measuring results of the TinySA is meant for the input level at the mixer.
The TinySA has an integrated programmable 0-31.5dB attenuator (PE4302 or equivalent), that is normally controlled by the TinySA firmware, to make sure, that the input at the mixer does not go beyond -25dBm.
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When you look very carefully at Wojtek's pictures you will see in the upper left area of the screen "Atten 22dB". With input signals in the -3dBm range exactly -25dBm will reach the mixer and guarantee a large spur free dynamic range.
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In most of my screen snapshots you will see "Atten -20dB" and a calculated (I configured "Level=-50dB" in the TinySA) input level at the input of the 50dB attenuator chain of 36dBm.
So the mixer will see 36dBm-50dB-20dB=-34dBm, definitely in the spur free range.
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Anyways spurs (usually intermodulation) could NEVER explain the spurs, that we see.
Particularly as you can exactly calculate the spur frequencies based on the zBitx internal frequencies...
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I hope that this helps to terminate this discussion about the quality of the TinySA measurement results and I also want to give Hans Summers a big thanks for his statement on the TinySA quality.
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73, Joerg - DB2OO
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Re: zBitx touchsreen issue
You made my day! Thank you, all ok now!
Wolfgang, DH2WS
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Re: zBitx touchsreen issue
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Sam and Wolf,
It looks like the front panel is exerting pressure on the display and pressing the screen causing it to "self-calibrate".? As Vince suggests, loosen the front panel bolts ever so slightly and perform the touch screen calibration routine. The touch screen calibration routine does not have a time out feature and sometimes when I run the touch screen calibration, the Pi boots up before I complete calibration and I can hear the audio from the Radio.
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73,
Ragav
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Re: zBitx touchsreen issue
Sam and Wolf,
It looks like the front panel is exerting pressure on the display and pressing the screen causing it to "self-calibrate".? As Vince suggests, loosen the front panel bolts ever so slightly and perform the touch screen calibration routine. The touch screen calibration routine does not have a time out feature and sometimes when I run the touch screen calibration, the Pi boots up before I complete calibration and I can hear the audio from the Radio.
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73,
Ragav
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
I have a professional grade Advantest R3361C. I was also on the beta testing team for TinySA. I'm sure since beta testing, it would likely have got better if anything, not worse. During my testing of TinySA I found that within it's specified operating conditions (meaning, don't overload it) it matched my professional instrument within 1 dB. SFDR appeared to be approximately 70 dB. Therefore if used correctly a TinySA has plenty more than sufficient dynamic range for testing harmonics and spurs of amateur radio transmitters. Which I found quite remarkable for such a well priced instrument.?
Note that RF shielding does not necessarily just consist of placing tin plate boxes around everything. Proper PCB layout and DC decoupling are at least as important.?
Crosstalk on Si5351A / MS5351M is a well-known issue which is solved by NOT heavily loading it's outputs. Heavily loading outputs also degrades phase noise and waveform. As far as I recall there isn't a datasheet specification involving crossralk. But experimental results with these ICs are well known and not new.
73 Hans G0UPL
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I would like to run my zbitx at 12vdc and up to 14vdc. ?I already swapped the linear regulator and the finals and re biased. ?It works great up to about 10vdc over that the receiver starts to attenuate. ?I am assuming this is because of the switching design for the bpf. ?I remember Farhan mentioning that there were components that could be swapped to allow for running up at 12vdc. ?Is it possible to get a rough list as to what these components are?
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Ryan
KK6DZB
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Don, he may not HAVE one.? ? He may consider spending $1400+ to get a Siglent or Rigol a high price to pay to check a $200 radio, right? We have a NICE discussion of why cheaper analyzers may fail with higher inputs..... it would be nice to see the data from a random number of transceivers measured on a Siglent or Rigol, and showing 0 out of 5 exceeding -43dBc, yes?
73, Gordon
Why don't you use a REAL spectrum analyzer, like an Agilent or
Rohde Schwarz?
Don in Texas, N5CID
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On
4/16/2025 10:35 PM, Ron, N6YWU via wrote:
Reducing the zBitx Drive
via its menu did seem to reduce the spurs relative to the
carrier, but not by quite enough.? I reduced the drive
until the TinySA was showing the carrier at -40 dB (that's
12 dB lower than my earlier test with the same attenuation
chain), but the high side spur didn't quite make it below
-80 dB.? The low side spur did.
73, Ron, n6ywu
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Why don't you use a REAL spectrum analyzer, like an Agilent or
Rohde Schwarz?
Don in Texas, N5CID
=============================================
On
4/16/2025 10:35 PM, Ron, N6YWU via groups.io wrote:
toggle quoted message
Show quoted text
Reducing the zBitx Drive
via its menu did seem to reduce the spurs relative to the
carrier, but not by quite enough. ?I reduced the drive
until the TinySA was showing the carrier at -40 dB (that's
12 dB lower than my earlier test with the same attenuation
chain), but the high side spur didn't quite make it below
-80 dB. ?The low side spur did.
73, Ron, n6ywu
_._,_._,_
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
Reducing the zBitx Drive via its menu did seem to reduce the spurs relative to the carrier, but not by quite enough. ?I reduced the drive until the TinySA was showing the carrier at -40 dB (that's 12 dB lower than my earlier test with the same attenuation chain), but the high side spur didn't quite make it below -80 dB. ?The low side spur did.
73, Ron, n6ywu
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
I added enough attenuation to reduce the carrier from my zBitx to -28 dBm, and still saw a spur at -60 dBm, which is only 32 dB below the carrier. ?That's a long way from -43 dBc. ?
But I have only one unit to test. ?How many units have been tested by the factory to determine whether there's any statistical variation within in the production volume.
73, Ron, n6ywu
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Re: Fixed: cw latency and wsjtx/flidigi sidetone
OK,? can people try this out: 1. Set the CW delay to 600 2.Now, try Iambic A and straight key, let's hear if there is a problem with these. We will move to Iambic B?if we can narrow the? problem down to (T/R delays and better keying with these two modes) Given that some people have no problems and others do with the sending, I am inclined to look at the precise differences in their sending practices. The software should be able to handle all of it. We will get there. As Eric Raymond says, "Give enough eyeballs, all bugs are shallow" - f
On Thu, Apr 17, 2025 at 6:36?AM santiagom5678 via <santiagom5678= [email protected]> wrote: I added some more videos after upgrading to 3.052
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It definitely does not work for me in Iambic B. I don't have a dual paddle otherwise I'd share a video of me butchering it.?
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The Farnsworth in some spots is due to the main main processor (my head).?
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On SK mode it works but there is an odd delay at first. Once it gets going it goes but when the T/R hits the delay is trigger again.?
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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting
There is intermodulation, without?doubt. However, my readings show that it is well within the FCC limits.? I took a closer look at the TinySA, it is an incredibly cool design ().? It uses an ADE-1 in the front-end. Which is a great mixer. It has an input intercept point of?+15 dBm. ().? Given that the?termination is bad at?RF port (the lpf should not terminate the reflected higher side image) and the?IF port (the bandpass filter provides high VSWR to all frequencies outside the band-pass), we expect a degradation down to?+10 dBm.? ? Let us take a moment to understand this.? 1. At an input of?+10 dBm, the intermodulation products (that is, the spurs), will be as loud as the signal itself?(they intercept the actual signal). This is under the ideal conditions of robust termination of the mixer at all the?three ports.? These are the third order intercepts that we are talking about. 2. As you back off the input signal to the SA, these spurs will drop away rapidly, for each dB of drop in the signal, the intermod products will go down by 3 dB. 3. Now, consider that the signal is at 0dBm. This means that we have backed off the signal by 10 dB, accordingly, the IMD products will be down by 30 dB.? 4. The compression in a diode mixer starts at around 15 dB below the intercept point. Thus we will also get a wrong reading of the actual signal which maybe down by a few dBs.
So, what is the way forward? With spectrum analyzers, we need to know the SFDR (spur-free dynamic range), that is, the highest and the lowest level signals that the SA will handle that we can reliably measure.?
Given all this, I would recommend measuring any transmitter output such that the signal being applied to the input is not more than -20 dBm.? My apprehensions about lack of shielding still hold. All this does not mean that there aren't any spurs in the zBitx. All superhets, esp the general coverage superhets (like the FT-817) will have spurs. They should be below the -43dBc level - f
Thanks for the information, Joerg
It could be intermodulation occurring in the SI5351a 40 MHz output transfering into the other? SI5351a output. Or something occurring in the 40 MHz/RF mixer. I am not sure of mixer levels.
If its related to that mixer then dropping the RF output level by 10 dB or so (say 0.5w or less, should clean things up.. My Zbitx is on its way so can't do any tests.?
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Re: AmateurRadioKits AGC Connection to uBitx v6
Hello Richard,
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If you can build from scratch, I would recommend the LED/LDR combination from VK3YE:
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I have built two of these for other hams.? Both worked well, in my opinion.? My current project is for another ham who provided the AmateurRadioKits AGC board to build and install.
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If I can not improve the response, I will rip out the AmateurRadioKits board and put in another LED/LDR-based build.? The issue with the home-built board is fitting it into the case.? I will need to work out another scheme as a lot is already going into the case.
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Attached is a PDF with a schematic and pictures of the board with my build connections:
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73
Evan
AC9TU
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Re: Fixed: cw latency and wsjtx/flidigi sidetone
I added some more videos after upgrading to 3.052
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It definitely does not work for me in Iambic B. I don't have a dual paddle otherwise I'd share a video of me butchering it.?
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The Farnsworth in some spots is due to the main main processor (my head).?
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On SK mode it works but there is an odd delay at first. Once it gets going it goes but when the T/R hits the delay is trigger again.?
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Joel Caulkins/N6ALT
Giuseppe Stancanelli - IU0OYC
Wolfgang
Sam Hanie