Date   
Re: Harmonics

Jack, W8TEE
 

Curtis:

I think there are two camps here: 1) those who feel that they cannot, in good conscience, operate any equipment that they know does not meet their ruling governance body (e.g., FCC), and 2) those who feel strongly that things are okay as long as I don't generate externalities that degrade or impair someone else's communications in any part of the spectrum. Al and I did a test on a stock µBITX and learned two things: 1) our $3600 commercial transceiver used for comparison was never "better" by more than 4dB on any band, and 2) the harmonics from the µBITX were so far below the noise level on all bands that it was undetectable.

Our tests, admittedly not as stringent as others, places me firmly in Camp 2 above. To me, its the Mathematician/Economist Problem (I'm an economist by training). Take a nude couple, place them in a room, and every 5 seconds, reduced the distance between them by 50%. To the mathematician, nothing ever happens. To the economist, game over in less than a few minutes. Camp 1 is the mathematician, Camp2 is the economist.

How could I choose anything other than Camp 2?

Jack, W8TEE

On Friday, August 10, 2018, 8:16:58 AM EDT, RCC WB5YYM <curtis03@...> wrote:


I too was wondering the same thing. I would think if you are using a resonant mono-band antenna, or using a tuner to tune the antenna that the harmonics measure at the output would have an even less chance of being radiated. With the ubitx being low power anyway, I suspect the radiated harmonic would be extremely minute, maybe in the low 1000ths of a watt. There has got to be some math out there some where to calculate this. 

A note about real vs. clone Arduino Nanos

lwhfac@...
 

Folks,
Another construction note. Always being prepared for failures, I purchased a few real Arduino Nanos as spares, plus I see many more applications for this platform in my lab. I noticed after I first fired up my uBitX with the included clone "Nano" that the TO-220 5V regulator was getting unusually hot. That's the one on the Raduino PWB. When that happened, I used one of the heatsinks from the IRF510s on that regulator (since I mounted the '510s directly onto the rear of the chassis I had the two supplied heatsinks left over). That is acceptable, but even that regulator heatsink gets warmer than I'd prefer. It seems to be OK by operating the rig for hours on end with no ill effects. The Nano draws 72 mA, the display backlight draws 30 mA and the Si 5351 synthesizer chip draws 50-ish mA for a total of roughly 150 mA. With a 12 volt input, that poor little regulator is dissipating just a smidge over a watt, which is too much for a non-heatsinked part.Then, on a whim, I replaced the clone Nano with a genuine one . The heatsink on that regulator was now MUCH cooler, well within anyone's standards, in fact, I probably could have left the heatsink off. What gives? It turns out that the clone Nano draws 72 mA! The real one draws 17 mA. WOW! I imagine that the culprit is that CH340 comms chip that everyone has talked about. Each Nano has an ATMega328 CPU on it so that isn't the current hog. An extra 50 mA or so could make a significant difference in a battery-operated portable device. It's no big deal if you're running the rig on a bench supply, but with batteries, every mA counts. The clone Nanos work as well as the genuine part functionally, except for that current issue. I know the clones are much cheaper, but here is a perfect example of, "you get what you pay for".
Larry N2AJX

Re: Harmonics measured by Warren. How bad?

m5fra2@...
 

I plan to not exceed 5W output and cannot understand the desire to squeeze every last watt out of any rig. Try QRP you will be amazed, 5W is close to 2 stops down on 100W!

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Dennis Zabawa
Sent: 10 August 2018 13:02
To: BITX20@groups.io
Subject: Re: [BITX20] Harmonics measured by Warren. How bad?

 

If one puts this in the perspective of a simple, inexpensive, multi-band, SSB/CW, transceiver that is built from "junk box" parts, the  uBITX meets most criteria well.  The apparent cure for it's ills appears to be proper alignment and tuneup.  What many users are trying to do is to create the equivalent of a commercial radio, for peanuts, by driving it to the limits and amplifying it.  Don't blame the radio when it doesn't work well in that environment.

Re: Harmonics

RCC WB5YYM
 

I too was wondering the same thing. I would think if you are using a resonant mono-band antenna, or using a tuner to tune the antenna that the harmonics measure at the output would have an even less chance of being radiated. With the ubitx being low power anyway, I suspect the radiated harmonic would be extremely minute, maybe in the low 1000ths of a watt. There has got to be some math out there some where to calculate this. 

Re: Harmonics measured by Warren. How bad?

m5fra2@...
 

  • Found a spectrum analyzer for $165

Beware, there can be lots of issues with old SAs

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Gordon Gibby
Sent: 10 August 2018 12:17
To: BITX20@groups.io
Subject: Re: [BITX20] Harmonics measured by Warren. How bad?

 

Hi iz—

 

Don’t know, but I wouldn’t recommend it. This is easy enough to fix, so why not fix it?  I would just use fixed bandpass output filters, but WINLINK & ALE both require fast electronic bandswitching. 

 

I picked up a little amp with a set of Lowpass  filters on eBay.   It will be sometime, but eventually I’ll add the extra relays and I think this will be a non-issue....  someone may easily beat me to it

 

Found a spectrum analyzer for $165, I may get that.   I’m getting old, and I don’t have forever.  

 

Gordon 

 

 


On Aug 10, 2018, at 06:56, iz oos <and2oosiz2@...> wrote:

Gordon, you want to use the uBitx with an amplifier. Some people warn not to use it with an amplifier which would make things worse. Suppose you use the uBitx as is with a push pull amplifier that has 43db attenuation on the third harmonics and beyond. My question is, would such a setup be comply to FCC or ITU?

 

Il 10/ago/2018 12:13, "Gordon Gibby" <ggibby@...> ha scritto:

Thanks much for the great information.  I’ll be able to share it with those building this rig in our group.  

 

I think personally it’s important that this design become more than compliant, even without special special adjustments.   I suspect that will be coming.  

 

When I am able, I am going to try the little daughter board with relays on the far side of the filters so as to avoid the “blow by” in the single relay switching both sides of a filter.  There will still need to be a bit of daisychaining. If that gets me down 10 DB or so allowing more of the excellent filters to shine through, I’ll be quite happy.  

 

I would like to be able to run this rig into an amplifier for WINLINK or ALE service, on the lower bands, and that would be important to accomplish before running it through an amplifier.  

 

The spurs are a different issue, and don’t affect bands that I use very often. So I’ll let others fix those. 

 

Cheers, 

 

Gordon

 

 

 

 

 


On Aug 10, 2018, at 03:45, Warren Allgyer <allgyer@...> wrote:

Ashhar

I respectfully disagree with the main point of your premise, to paraphrase: "The uBitx is ok because it has less spurious emissions than are allowed for a commercial amateur transceiver operating at 100 watts or a transceiver/amplifier operating at 1500 watts". There are two things wrong with this premise, 1) Modern commercial transceivers are specified to have emissions at least 50 dB below carrier level; many are specified at 60 dB or more. Such transceivers have spurious emissions far below those of the uBitx even when operated at 100 or 200 watts. 2) Unfortunately that is not how the rules are written or applied by the respective governing bodies. The allowed level of emissions must be 43 dB below carrier level, 50 dB in most countries other than the USA, regardless what that carrier level may be. That may not seem logical but that is the rule that is a condition of our license and that we committed to uphold when we received it.

The compliance of my uBitx with these rules is summarized here:

<Screen Shot 2018_08_10 at 2.51.25 AM.jpg>

You have addressed only the recently discovered harmonics issues. And my unit, as you have noted, is not disqualified by excessive harmonics on bands above 17 meters. Unfortunately, on those bands, it is disqualified by the previously discovered "45 MHz minus carrier" spurs.

You say "First: the trouble seems to be more with CW than SSB harmonics. We can reduce the CW level by decreasing the CW drive level."

Perhaps, but I think you will find that the harmonics on CW are far more a function of putting the harmonic rich square wave output of the Si5351 directly into the transmitter signal chain without filtering. The reason the CW versus SSB issue disappears in the high bands is because the circuitry itself acts as a filter "rounding" out the square waves at these higher frequencies. I don't think your proposed drive level change will affect CW harmonics but it is worth a try.

You have written "Second: the alignment as it comes out from HF signals will show far better harmonic suppression than being reported here. For instance, the -38 dbc on 20 meters and -30 db on 40 meters will almost disappear if you balanace it out with the bias on the IRF510s. The factory alignment works like this : First crank up both the IRF510s for 100 ma standing current on each, then tweak one of them to null out the harmonics. It is like balancing out the carrier on diode modulator."

The harmonics causing the problem in my screen shots are odd harmonics; 3rd, 5th, 7th, 9th etc. The alignment procedure you recommend only affects even harmonics due to the cancellation effect of the push-pull PA. It has no effect whatsoever on odd harmonics and, in fact, had been optimized just as you describe before my testing.

You say: "Third: below 14 MHz, the IRF510s are distorting with too much drive. If you back off the drive to adjust to a leve of 7 watts, the harmonics will climb down to be within the spec."

Sorry, but not so for my tests. As noted in my text, all harmonic screenshots were taken with drive reduced to result in a consistent power output for each band of +33 dBm, 2 watts. This was done precisely to avoid overdriving any stage of the transmission chain. At maximum drive, particularly on 80 and 40 meters the harmonics are considerably worse.

Your filter designs and components as supplied are adequate for the PA filtering application. Removed from the board and laid out in a linear fashion with no relays, the filters exhibit well over 55 dB of attenuation at the 3rd harmonic and higher for each band. The primary limiting factor is the strategy of running the input and output of each filter through at least one common relay; lower bands do this with two or all three of the relays. Input to output crosstalk within the relay becomes the first and most substantial contributor to the "blow-by" of harmonics bypassing the filters. The second factor is the "daisy chaining" of the low frequency signals through multiple relays. Finally, a high power PA harmonic filter must have extremely high overall isolation between the input and output of the assembly. The long traces and circuitous routing on the board to connect all of these relays contributes to lack of input/output isolation. When laid out on the board and routed through the relays the filters exhibit on the order of 25 dB attenuation at harmonic frequencies; far too little to be compliant.

The relays per se are not the problem.

It may be possible to make the uBitx compliant with only better PA filter layout: No sharing of relays between filter inputs and outputs, no daisy-chaining of relays, more straightforward PCB layout. However, due to the "45 MHz - carrier" spur issue such filters would need to be BPF rather than LPT. Alternatively, a 4-6 filter assembly, switched in conjunction with the PA filter and placed between the first mixer and the drive chain would likely clean up the signals to the point that the existing filter arrangement may work.

Based on the discussion here and a parallel one on the Facebook uBitx page, I do not believe my results are "sample of one" or the result of a defective unit. That, however, remains a possibility until someone publishes data assembled with similar care to refute them.

I love the concept of uBitx. I want it to work and work well. I sympathize with the pragmatic concept that "it makes less spur power than an high power commercial rig" but that is not the rule. And you can already see the number of people who connect the uBitx to linear amplifiers on the assumption they are starting out with a compliant radio but they are not. 

I cannot, in good conscience, put my unit on the air as it stands. Each amateur radio operator needs to be guided by his or her conscience in this matter. But if the decision is made to go ahead it should be made with the full knowledge that it is a violation to do so.

Thanks for soliciting responses and for listening.

WA8TOD 

Re: Harmonics measured by Warren. How bad?

m5fra2@...
 

Good to see you have not been put off the rig Gordon. I have seen reports  on other channels of tests that do not confirm the current stuff that is flying around.

 

Colin – M5FRA

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Gordon Gibby
Sent: 10 August 2018 11:14
To: BITX20@groups.io
Subject: Re: [BITX20] Harmonics measured by Warren. How bad?

 

Thanks much for the great information.  I’ll be able to share it with those building this rig in our group.  

 

I think personally it’s important that this design become more than compliant, even without special special adjustments.   I suspect that will be coming.  

 

When I am able, I am going to try the little daughter board with relays on the far side of the filters so as to avoid the “blow by” in the single relay switching both sides of a filter.  There will still need to be a bit of daisychaining. If that gets me down 10 DB or so allowing more of the excellent filters to shine through, I’ll be quite happy.  

 

I would like to be able to run this rig into an amplifier for WINLINK or ALE service, on the lower bands, and that would be important to accomplish before running it through an amplifier.  

 

The spurs are a different issue, and don’t affect bands that I use very often. So I’ll let others fix those. 

 

Cheers, 

 

Gordon

 

 

 

 

 


On Aug 10, 2018, at 03:45, Warren Allgyer <allgyer@...> wrote:

Ashhar

I respectfully disagree with the main point of your premise, to paraphrase: "The uBitx is ok because it has less spurious emissions than are allowed for a commercial amateur transceiver operating at 100 watts or a transceiver/amplifier operating at 1500 watts". There are two things wrong with this premise, 1) Modern commercial transceivers are specified to have emissions at least 50 dB below carrier level; many are specified at 60 dB or more. Such transceivers have spurious emissions far below those of the uBitx even when operated at 100 or 200 watts. 2) Unfortunately that is not how the rules are written or applied by the respective governing bodies. The allowed level of emissions must be 43 dB below carrier level, 50 dB in most countries other than the USA, regardless what that carrier level may be. That may not seem logical but that is the rule that is a condition of our license and that we committed to uphold when we received it.

The compliance of my uBitx with these rules is summarized here:

<Screen Shot 2018_08_10 at 2.51.25 AM.jpg>

You have addressed only the recently discovered harmonics issues. And my unit, as you have noted, is not disqualified by excessive harmonics on bands above 17 meters. Unfortunately, on those bands, it is disqualified by the previously discovered "45 MHz minus carrier" spurs.

You say "First: the trouble seems to be more with CW than SSB harmonics. We can reduce the CW level by decreasing the CW drive level."

Perhaps, but I think you will find that the harmonics on CW are far more a function of putting the harmonic rich square wave output of the Si5351 directly into the transmitter signal chain without filtering. The reason the CW versus SSB issue disappears in the high bands is because the circuitry itself acts as a filter "rounding" out the square waves at these higher frequencies. I don't think your proposed drive level change will affect CW harmonics but it is worth a try.

You have written "Second: the alignment as it comes out from HF signals will show far better harmonic suppression than being reported here. For instance, the -38 dbc on 20 meters and -30 db on 40 meters will almost disappear if you balanace it out with the bias on the IRF510s. The factory alignment works like this : First crank up both the IRF510s for 100 ma standing current on each, then tweak one of them to null out the harmonics. It is like balancing out the carrier on diode modulator."

The harmonics causing the problem in my screen shots are odd harmonics; 3rd, 5th, 7th, 9th etc. The alignment procedure you recommend only affects even harmonics due to the cancellation effect of the push-pull PA. It has no effect whatsoever on odd harmonics and, in fact, had been optimized just as you describe before my testing.

You say: "Third: below 14 MHz, the IRF510s are distorting with too much drive. If you back off the drive to adjust to a leve of 7 watts, the harmonics will climb down to be within the spec."

Sorry, but not so for my tests. As noted in my text, all harmonic screenshots were taken with drive reduced to result in a consistent power output for each band of +33 dBm, 2 watts. This was done precisely to avoid overdriving any stage of the transmission chain. At maximum drive, particularly on 80 and 40 meters the harmonics are considerably worse.

Your filter designs and components as supplied are adequate for the PA filtering application. Removed from the board and laid out in a linear fashion with no relays, the filters exhibit well over 55 dB of attenuation at the 3rd harmonic and higher for each band. The primary limiting factor is the strategy of running the input and output of each filter through at least one common relay; lower bands do this with two or all three of the relays. Input to output crosstalk within the relay becomes the first and most substantial contributor to the "blow-by" of harmonics bypassing the filters. The second factor is the "daisy chaining" of the low frequency signals through multiple relays. Finally, a high power PA harmonic filter must have extremely high overall isolation between the input and output of the assembly. The long traces and circuitous routing on the board to connect all of these relays contributes to lack of input/output isolation. When laid out on the board and routed through the relays the filters exhibit on the order of 25 dB attenuation at harmonic frequencies; far too little to be compliant.

The relays per se are not the problem.

It may be possible to make the uBitx compliant with only better PA filter layout: No sharing of relays between filter inputs and outputs, no daisy-chaining of relays, more straightforward PCB layout. However, due to the "45 MHz - carrier" spur issue such filters would need to be BPF rather than LPT. Alternatively, a 4-6 filter assembly, switched in conjunction with the PA filter and placed between the first mixer and the drive chain would likely clean up the signals to the point that the existing filter arrangement may work.

Based on the discussion here and a parallel one on the Facebook uBitx page, I do not believe my results are "sample of one" or the result of a defective unit. That, however, remains a possibility until someone publishes data assembled with similar care to refute them.

I love the concept of uBitx. I want it to work and work well. I sympathize with the pragmatic concept that "it makes less spur power than an high power commercial rig" but that is not the rule. And you can already see the number of people who connect the uBitx to linear amplifiers on the assumption they are starting out with a compliant radio but they are not. 

I cannot, in good conscience, put my unit on the air as it stands. Each amateur radio operator needs to be guided by his or her conscience in this matter. But if the decision is made to go ahead it should be made with the full knowledge that it is a violation to do so.

Thanks for soliciting responses and for listening.

WA8TOD 

Re: Harmonics measured by Warren. How bad?

Dennis Zabawa
 

If one puts this in the perspective of a simple, inexpensive, multi-band, SSB/CW, transceiver that is built from "junk box" parts, the  uBITX meets most criteria well.  The apparent cure for it's ills appears to be proper alignment and tuneup.  What many users are trying to do is to create the equivalent of a commercial radio, for peanuts, by driving it to the limits and amplifying it.  Don't blame the radio when it doesn't work well in that environment.

Harmonics

 

While we are on the topic of harmonics:

If a rig does have spurs or harmonics in the output the antenna MAY not radiate much of it.

A 40M dipole will radiate 15M spurs or harmonics. The same will be greatly attenuated if harmonics/spurs
are present on say 20M or on a frequency that the antenna is not resonant.

I have not done experiments on this thought but some of you may have given it more thought or
even done some tests.

Cheers

--
Raj, vu2zap
Bengaluru, South India.

Re: Harmonics measured by Warren. How bad?

Gordon Gibby <ggibby@...>
 

Hi iz—

Don’t know, but I wouldn’t recommend it. This is easy enough to fix, so why not fix it?  I would just use fixed bandpass output filters, but WINLINK & ALE both require fast electronic bandswitching. 

I picked up a little amp with a set of Lowpass  filters on eBay.   It will be sometime, but eventually I’ll add the extra relays and I think this will be a non-issue....  someone may easily beat me to it

Found a spectrum analyzer for $165, I may get that.   I’m getting old, and I don’t have forever.  

Gordon 



On Aug 10, 2018, at 06:56, iz oos <and2oosiz2@...> wrote:

Gordon, you want to use the uBitx with an amplifier. Some people warn not to use it with an amplifier which would make things worse. Suppose you use the uBitx as is with a push pull amplifier that has 43db attenuation on the third harmonics and beyond. My question is, would such a setup be comply to FCC or ITU?


Il 10/ago/2018 12:13, "Gordon Gibby" <ggibby@...> ha scritto:
Thanks much for the great information.  I’ll be able to share it with those building this rig in our group.  

I think personally it’s important that this design become more than compliant, even without special special adjustments.   I suspect that will be coming.  

When I am able, I am going to try the little daughter board with relays on the far side of the filters so as to avoid the “blow by” in the single relay switching both sides of a filter.  There will still need to be a bit of daisychaining. If that gets me down 10 DB or so allowing more of the excellent filters to shine through, I’ll be quite happy.  

I would like to be able to run this rig into an amplifier for WINLINK or ALE service, on the lower bands, and that would be important to accomplish before running it through an amplifier.  

The spurs are a different issue, and don’t affect bands that I use very often. So I’ll let others fix those. 

Cheers, 

Gordon
 






On Aug 10, 2018, at 03:45, Warren Allgyer <allgyer@...> wrote:

Ashhar

I respectfully disagree with the main point of your premise, to paraphrase: "The uBitx is ok because it has less spurious emissions than are allowed for a commercial amateur transceiver operating at 100 watts or a transceiver/amplifier operating at 1500 watts". There are two things wrong with this premise, 1) Modern commercial transceivers are specified to have emissions at least 50 dB below carrier level; many are specified at 60 dB or more. Such transceivers have spurious emissions far below those of the uBitx even when operated at 100 or 200 watts. 2) Unfortunately that is not how the rules are written or applied by the respective governing bodies. The allowed level of emissions must be 43 dB below carrier level, 50 dB in most countries other than the USA, regardless what that carrier level may be. That may not seem logical but that is the rule that is a condition of our license and that we committed to uphold when we received it.

The compliance of my uBitx with these rules is summarized here:

<Screen Shot 2018_08_10 at 2.51.25 AM.jpg>

You have addressed only the recently discovered harmonics issues. And my unit, as you have noted, is not disqualified by excessive harmonics on bands above 17 meters. Unfortunately, on those bands, it is disqualified by the previously discovered "45 MHz minus carrier" spurs.

You say "First: the trouble seems to be more with CW than SSB harmonics. We can reduce the CW level by decreasing the CW drive level."

Perhaps, but I think you will find that the harmonics on CW are far more a function of putting the harmonic rich square wave output of the Si5351 directly into the transmitter signal chain without filtering. The reason the CW versus SSB issue disappears in the high bands is because the circuitry itself acts as a filter "rounding" out the square waves at these higher frequencies. I don't think your proposed drive level change will affect CW harmonics but it is worth a try.

You have written "Second: the alignment as it comes out from HF signals will show far better harmonic suppression than being reported here. For instance, the -38 dbc on 20 meters and -30 db on 40 meters will almost disappear if you balanace it out with the bias on the IRF510s. The factory alignment works like this : First crank up both the IRF510s for 100 ma standing current on each, then tweak one of them to null out the harmonics. It is like balancing out the carrier on diode modulator."

The harmonics causing the problem in my screen shots are odd harmonics; 3rd, 5th, 7th, 9th etc. The alignment procedure you recommend only affects even harmonics due to the cancellation effect of the push-pull PA. It has no effect whatsoever on odd harmonics and, in fact, had been optimized just as you describe before my testing.

You say: "Third: below 14 MHz, the IRF510s are distorting with too much drive. If you back off the drive to adjust to a leve of 7 watts, the harmonics will climb down to be within the spec."

Sorry, but not so for my tests. As noted in my text, all harmonic screenshots were taken with drive reduced to result in a consistent power output for each band of +33 dBm, 2 watts. This was done precisely to avoid overdriving any stage of the transmission chain. At maximum drive, particularly on 80 and 40 meters the harmonics are considerably worse.

Your filter designs and components as supplied are adequate for the PA filtering application. Removed from the board and laid out in a linear fashion with no relays, the filters exhibit well over 55 dB of attenuation at the 3rd harmonic and higher for each band. The primary limiting factor is the strategy of running the input and output of each filter through at least one common relay; lower bands do this with two or all three of the relays. Input to output crosstalk within the relay becomes the first and most substantial contributor to the "blow-by" of harmonics bypassing the filters. The second factor is the "daisy chaining" of the low frequency signals through multiple relays. Finally, a high power PA harmonic filter must have extremely high overall isolation between the input and output of the assembly. The long traces and circuitous routing on the board to connect all of these relays contributes to lack of input/output isolation. When laid out on the board and routed through the relays the filters exhibit on the order of 25 dB attenuation at harmonic frequencies; far too little to be compliant.

The relays per se are not the problem.

It may be possible to make the uBitx compliant with only better PA filter layout: No sharing of relays between filter inputs and outputs, no daisy-chaining of relays, more straightforward PCB layout. However, due to the "45 MHz - carrier" spur issue such filters would need to be BPF rather than LPT. Alternatively, a 4-6 filter assembly, switched in conjunction with the PA filter and placed between the first mixer and the drive chain would likely clean up the signals to the point that the existing filter arrangement may work.

Based on the discussion here and a parallel one on the Facebook uBitx page, I do not believe my results are "sample of one" or the result of a defective unit. That, however, remains a possibility until someone publishes data assembled with similar care to refute them.

I love the concept of uBitx. I want it to work and work well. I sympathize with the pragmatic concept that "it makes less spur power than an high power commercial rig" but that is not the rule. And you can already see the number of people who connect the uBitx to linear amplifiers on the assumption they are starting out with a compliant radio but they are not. 

I cannot, in good conscience, put my unit on the air as it stands. Each amateur radio operator needs to be guided by his or her conscience in this matter. But if the decision is made to go ahead it should be made with the full knowledge that it is a violation to do so.

Thanks for soliciting responses and for listening.

WA8TOD 

Re: Harmonics measured by Warren. How bad?

iz oos
 

Gordon, you want to use the uBitx with an amplifier. Some people warn not to use it with an amplifier which would make things worse. Suppose you use the uBitx as is with a push pull amplifier that has 43db attenuation on the third harmonics and beyond. My question is, would such a setup be comply to FCC or ITU?


Il 10/ago/2018 12:13, "Gordon Gibby" <ggibby@...> ha scritto:
Thanks much for the great information.  I’ll be able to share it with those building this rig in our group.  

I think personally it’s important that this design become more than compliant, even without special special adjustments.   I suspect that will be coming.  

When I am able, I am going to try the little daughter board with relays on the far side of the filters so as to avoid the “blow by” in the single relay switching both sides of a filter.  There will still need to be a bit of daisychaining. If that gets me down 10 DB or so allowing more of the excellent filters to shine through, I’ll be quite happy.  

I would like to be able to run this rig into an amplifier for WINLINK or ALE service, on the lower bands, and that would be important to accomplish before running it through an amplifier.  

The spurs are a different issue, and don’t affect bands that I use very often. So I’ll let others fix those. 

Cheers, 

Gordon
 






On Aug 10, 2018, at 03:45, Warren Allgyer <allgyer@...> wrote:

Ashhar

I respectfully disagree with the main point of your premise, to paraphrase: "The uBitx is ok because it has less spurious emissions than are allowed for a commercial amateur transceiver operating at 100 watts or a transceiver/amplifier operating at 1500 watts". There are two things wrong with this premise, 1) Modern commercial transceivers are specified to have emissions at least 50 dB below carrier level; many are specified at 60 dB or more. Such transceivers have spurious emissions far below those of the uBitx even when operated at 100 or 200 watts. 2) Unfortunately that is not how the rules are written or applied by the respective governing bodies. The allowed level of emissions must be 43 dB below carrier level, 50 dB in most countries other than the USA, regardless what that carrier level may be. That may not seem logical but that is the rule that is a condition of our license and that we committed to uphold when we received it.

The compliance of my uBitx with these rules is summarized here:

<Screen Shot 2018_08_10 at 2.51.25 AM.jpg>

You have addressed only the recently discovered harmonics issues. And my unit, as you have noted, is not disqualified by excessive harmonics on bands above 17 meters. Unfortunately, on those bands, it is disqualified by the previously discovered "45 MHz minus carrier" spurs.

You say "First: the trouble seems to be more with CW than SSB harmonics. We can reduce the CW level by decreasing the CW drive level."

Perhaps, but I think you will find that the harmonics on CW are far more a function of putting the harmonic rich square wave output of the Si5351 directly into the transmitter signal chain without filtering. The reason the CW versus SSB issue disappears in the high bands is because the circuitry itself acts as a filter "rounding" out the square waves at these higher frequencies. I don't think your proposed drive level change will affect CW harmonics but it is worth a try.

You have written "Second: the alignment as it comes out from HF signals will show far better harmonic suppression than being reported here. For instance, the -38 dbc on 20 meters and -30 db on 40 meters will almost disappear if you balanace it out with the bias on the IRF510s. The factory alignment works like this : First crank up both the IRF510s for 100 ma standing current on each, then tweak one of them to null out the harmonics. It is like balancing out the carrier on diode modulator."

The harmonics causing the problem in my screen shots are odd harmonics; 3rd, 5th, 7th, 9th etc. The alignment procedure you recommend only affects even harmonics due to the cancellation effect of the push-pull PA. It has no effect whatsoever on odd harmonics and, in fact, had been optimized just as you describe before my testing.

You say: "Third: below 14 MHz, the IRF510s are distorting with too much drive. If you back off the drive to adjust to a leve of 7 watts, the harmonics will climb down to be within the spec."

Sorry, but not so for my tests. As noted in my text, all harmonic screenshots were taken with drive reduced to result in a consistent power output for each band of +33 dBm, 2 watts. This was done precisely to avoid overdriving any stage of the transmission chain. At maximum drive, particularly on 80 and 40 meters the harmonics are considerably worse.

Your filter designs and components as supplied are adequate for the PA filtering application. Removed from the board and laid out in a linear fashion with no relays, the filters exhibit well over 55 dB of attenuation at the 3rd harmonic and higher for each band. The primary limiting factor is the strategy of running the input and output of each filter through at least one common relay; lower bands do this with two or all three of the relays. Input to output crosstalk within the relay becomes the first and most substantial contributor to the "blow-by" of harmonics bypassing the filters. The second factor is the "daisy chaining" of the low frequency signals through multiple relays. Finally, a high power PA harmonic filter must have extremely high overall isolation between the input and output of the assembly. The long traces and circuitous routing on the board to connect all of these relays contributes to lack of input/output isolation. When laid out on the board and routed through the relays the filters exhibit on the order of 25 dB attenuation at harmonic frequencies; far too little to be compliant.

The relays per se are not the problem.

It may be possible to make the uBitx compliant with only better PA filter layout: No sharing of relays between filter inputs and outputs, no daisy-chaining of relays, more straightforward PCB layout. However, due to the "45 MHz - carrier" spur issue such filters would need to be BPF rather than LPT. Alternatively, a 4-6 filter assembly, switched in conjunction with the PA filter and placed between the first mixer and the drive chain would likely clean up the signals to the point that the existing filter arrangement may work.

Based on the discussion here and a parallel one on the Facebook uBitx page, I do not believe my results are "sample of one" or the result of a defective unit. That, however, remains a possibility until someone publishes data assembled with similar care to refute them.

I love the concept of uBitx. I want it to work and work well. I sympathize with the pragmatic concept that "it makes less spur power than an high power commercial rig" but that is not the rule. And you can already see the number of people who connect the uBitx to linear amplifiers on the assumption they are starting out with a compliant radio but they are not. 

I cannot, in good conscience, put my unit on the air as it stands. Each amateur radio operator needs to be guided by his or her conscience in this matter. But if the decision is made to go ahead it should be made with the full knowledge that it is a violation to do so.

Thanks for soliciting responses and for listening.

WA8TOD 

Re: Harmonics measured by Warren. How bad?

Gordon Gibby <ggibby@...>
 

Thanks much for the great information.  I’ll be able to share it with those building this rig in our group.  

I think personally it’s important that this design become more than compliant, even without special special adjustments.   I suspect that will be coming.  

When I am able, I am going to try the little daughter board with relays on the far side of the filters so as to avoid the “blow by” in the single relay switching both sides of a filter.  There will still need to be a bit of daisychaining. If that gets me down 10 DB or so allowing more of the excellent filters to shine through, I’ll be quite happy.  

I would like to be able to run this rig into an amplifier for WINLINK or ALE service, on the lower bands, and that would be important to accomplish before running it through an amplifier.  

The spurs are a different issue, and don’t affect bands that I use very often. So I’ll let others fix those. 

Cheers, 

Gordon
 






On Aug 10, 2018, at 03:45, Warren Allgyer <allgyer@...> wrote:

Ashhar

I respectfully disagree with the main point of your premise, to paraphrase: "The uBitx is ok because it has less spurious emissions than are allowed for a commercial amateur transceiver operating at 100 watts or a transceiver/amplifier operating at 1500 watts". There are two things wrong with this premise, 1) Modern commercial transceivers are specified to have emissions at least 50 dB below carrier level; many are specified at 60 dB or more. Such transceivers have spurious emissions far below those of the uBitx even when operated at 100 or 200 watts. 2) Unfortunately that is not how the rules are written or applied by the respective governing bodies. The allowed level of emissions must be 43 dB below carrier level, 50 dB in most countries other than the USA, regardless what that carrier level may be. That may not seem logical but that is the rule that is a condition of our license and that we committed to uphold when we received it.

The compliance of my uBitx with these rules is summarized here:

<Screen Shot 2018_08_10 at 2.51.25 AM.jpg>

You have addressed only the recently discovered harmonics issues. And my unit, as you have noted, is not disqualified by excessive harmonics on bands above 17 meters. Unfortunately, on those bands, it is disqualified by the previously discovered "45 MHz minus carrier" spurs.

You say "First: the trouble seems to be more with CW than SSB harmonics. We can reduce the CW level by decreasing the CW drive level."

Perhaps, but I think you will find that the harmonics on CW are far more a function of putting the harmonic rich square wave output of the Si5351 directly into the transmitter signal chain without filtering. The reason the CW versus SSB issue disappears in the high bands is because the circuitry itself acts as a filter "rounding" out the square waves at these higher frequencies. I don't think your proposed drive level change will affect CW harmonics but it is worth a try.

You have written "Second: the alignment as it comes out from HF signals will show far better harmonic suppression than being reported here. For instance, the -38 dbc on 20 meters and -30 db on 40 meters will almost disappear if you balanace it out with the bias on the IRF510s. The factory alignment works like this : First crank up both the IRF510s for 100 ma standing current on each, then tweak one of them to null out the harmonics. It is like balancing out the carrier on diode modulator."

The harmonics causing the problem in my screen shots are odd harmonics; 3rd, 5th, 7th, 9th etc. The alignment procedure you recommend only affects even harmonics due to the cancellation effect of the push-pull PA. It has no effect whatsoever on odd harmonics and, in fact, had been optimized just as you describe before my testing.

You say: "Third: below 14 MHz, the IRF510s are distorting with too much drive. If you back off the drive to adjust to a leve of 7 watts, the harmonics will climb down to be within the spec."

Sorry, but not so for my tests. As noted in my text, all harmonic screenshots were taken with drive reduced to result in a consistent power output for each band of +33 dBm, 2 watts. This was done precisely to avoid overdriving any stage of the transmission chain. At maximum drive, particularly on 80 and 40 meters the harmonics are considerably worse.

Your filter designs and components as supplied are adequate for the PA filtering application. Removed from the board and laid out in a linear fashion with no relays, the filters exhibit well over 55 dB of attenuation at the 3rd harmonic and higher for each band. The primary limiting factor is the strategy of running the input and output of each filter through at least one common relay; lower bands do this with two or all three of the relays. Input to output crosstalk within the relay becomes the first and most substantial contributor to the "blow-by" of harmonics bypassing the filters. The second factor is the "daisy chaining" of the low frequency signals through multiple relays. Finally, a high power PA harmonic filter must have extremely high overall isolation between the input and output of the assembly. The long traces and circuitous routing on the board to connect all of these relays contributes to lack of input/output isolation. When laid out on the board and routed through the relays the filters exhibit on the order of 25 dB attenuation at harmonic frequencies; far too little to be compliant.

The relays per se are not the problem.

It may be possible to make the uBitx compliant with only better PA filter layout: No sharing of relays between filter inputs and outputs, no daisy-chaining of relays, more straightforward PCB layout. However, due to the "45 MHz - carrier" spur issue such filters would need to be BPF rather than LPT. Alternatively, a 4-6 filter assembly, switched in conjunction with the PA filter and placed between the first mixer and the drive chain would likely clean up the signals to the point that the existing filter arrangement may work.

Based on the discussion here and a parallel one on the Facebook uBitx page, I do not believe my results are "sample of one" or the result of a defective unit. That, however, remains a possibility until someone publishes data assembled with similar care to refute them.

I love the concept of uBitx. I want it to work and work well. I sympathize with the pragmatic concept that "it makes less spur power than an high power commercial rig" but that is not the rule. And you can already see the number of people who connect the uBitx to linear amplifiers on the assumption they are starting out with a compliant radio but they are not. 

I cannot, in good conscience, put my unit on the air as it stands. Each amateur radio operator needs to be guided by his or her conscience in this matter. But if the decision is made to go ahead it should be made with the full knowledge that it is a violation to do so.

Thanks for soliciting responses and for listening.

WA8TOD 

Re: BITX40: Qui peut m’aider ? Who can help me ?

Vic WA4THR
 

Généralement, les erreurs sont dues au fait qu'une bibliothèque donnée, telle que la bibliothèque "PinChangeInterrupt", n'a pas été incluse dans le programme IDE Arduino avant la compilation. S'il vous plaît voir les instructions à cette URL:

https://github.com/amunters/bitx40/blob/master/installation_instructions/0-software-installation.md

Toutefois, si ce n’est pas le cas, veuillez indiquer les erreurs que vous obtenez. Je pense que vous serez vraiment heureux avec ce croquis. Allard a fait un travail magistral en le créant.

73, =Vic=
WA4THR

Re: New Warning on uBITx.net

Marc Jones
 

You don't read to well ... I stated  ' The Wright brothers to NASA ' ...


On Thu, 9 Aug 2018 at 15:25, iz oos
<and2oosiz2@...> wrote:

Are you comparing Yaesu to NASA? What about the IF filter issue they had for years in some models (not the 817)? I think to certain extent simplicity in design is a plus, not a minus. The uBitx is a clever design, and we, actually Warren, now have discovered it had an allegedly important issue which can be solved or worked around. The uBitx has also the double of power compared to the 817. Btw I acknowledge that the 817 had been a clever design considering it has 6m, 2m and 70cm, all mode.


Il 09/ago/2018 16:11, "Marc Jones via Groups.Io" <gw0wvl=yahoo.co.uk@groups.io> ha scritto:
Why would you think a 'Kit radio' should work better than a Yaesu FT-817 , Yaesu  no doubt plough hundreds of thousands into design, With an Army or engineers , Where as The Bitx radios are made and designed on a budget, Using minimal parts to keep it cheap by just a few people ..... Your basically comparing  the Wright brothers to NASA .... I mean Really .

Gw0wvl


On Wed, 8 Aug 2018 at 20:21, iz oos

I should feel even more betrayed than you as I was quite sure it was better than the 817 and alike. I think Farhan has done one mistake. But I would not put on him more pressure. He knows it. That mistake for me is nothing. Ham radio is a hobby. In the worst scenario I threw away 109usd but it gave me the opportunity to learn something. If you buy an 817 my guess you learn not much more than pushing the buttons.


Il 08/ago/2018 20:04, "ltj_designs" <arm@...> ha scritto:
I am very glad Mike posted the warning.  I feel the urgency is appropriate.

I am a brand new owner of a uBITx and I feel betrayed.  If you are going to sell or publish the plans for an amateur radio transmitter and you list the strengths and weaknesses, the reasonable assumption is that the transmitted signal is clean.  At the very least you indicate the output has not been tested for spurious emissions. For the record, I have been directly involved in the design publication and sales of related ham projects, so I have walked in those shoes. Had I known about the ineffective output filtering, I would not have purchased the radio board. I was prepared to build in a digital interface, a better audio amplifier and a SWR meter to customize the transceiver for my needs. I was not prepared for a "complete radio" with a dirty output.  

I have contacted a friend who has built and sold LPF boards for QRP rigs in the past and alerted him to the problem. I hope he looks into providing a short or medium-term solution for those who already own the kit.  I can envision a solution using a daughter board and a few bits from one of the Arduino variants.  Sadly, the price would probably push the project near the cost of other QRP rigs that come in a custom case.  

Note, I do not consider a manually-operated or costly outboard LPF filter a "fix". It is a work-around, at best. I am waiting for the arrival of a new spectrum analyzer.  When it gets here, I will verify the problem for myself. Then, I need to decide whether simply trashing the unit is the best (including most cost-effective) step forward for achieving my original goal. It is sad and a little harsh, but a natural consequence of shipping a transmitter without testing the spectral purity. 

Re: One question only...

Tom, wb6b
 

I was reading and found this data sheet for the RTL-SDR dongle. https://www.rtl-sdr.com/wp-content/uploads/2018/02/RTL-SDR-Blog-V3-Datasheet.pdf
The information explains in the direct conversion mode there can be images around the 14.4 Mhz point because the sample rate in the direct mode is 28.8 Mhz. Maybe that was the image issue that was sticking around in the back of my mind about the direct mode.

The Red Pitaya info is really interesting. In a distant past life I designed with Xilinx programable Logic Cell Arrays and designed gate array ASICs. It would be nice to have a development board on my desk to play with. Been messing some with the AWS FPGA cloud instances. But, something affordable that I can hook my own wires onto is great.

Tom, wb6b

Re: BITX40: Qui peut m’aider ? Who can help me ?

F1BFU - Fr - 79
 

Bonjour

Je n'ai qu'un uBitx avec la version usine du firmware donc je n'ai pas encore commencé à remplacer le logiciel par une nouvelle version.
Je fais déjà quelques modifications hardware avant de changer de version du firmware.

Votre bitx40 est un modèle tout monté par Farhan ou l'avez vous monté vous-même ?
Voulez-vous changer les paramètres de l'appareil ou charger une nouvelle version du logiciel ?
Si vous voulez charger une nouvelle version du logiciel, faîtes-vous la compilation à partir des sources ou chargez-vous des fichiers .hex ?

Donnez-nous plus d'informations.

Gilles de F1BFU / FR

Le ven. 10 août 2018 à 09:56, f6cxo <f6cxo@...> a écrit :

Bonjour Laurent

Mon Anglais étant inexistant, j'utilise GOOGLE traduction etl'échange est long.

J'essaie de programmer la version 1.28 sur mon BITX40 et il y a des messages d'erreur qui empêchent la programmation.

73 Gégé

 

 

 

 

> Message du 09/08/18 21:15
> De : "DREYFUSS Laurent via Groups.Io" <f4czi=yahoo.fr@groups.io>
> A : "BITX20@groups.io" <BITX20@groups.io>
> Copie à :
> Objet : Re: [BITX20] BITX40: Qui peut m’aider ? Who can help me ?
>
>
Bonjour Gégé,
 
C'est vrai qu'un peu plus de participation en français serait la bienvenue. Par contre, une réponse directe prive automatiquement les autres personnes intéressées par le sujet d'informations pouvant êtres utiles.

>
73

>
Laurent F8CZI
>
 



De : f6cxo <f6cxo@...>
À : BITX20@groups.io
Envoyé le : Jeudi 9 août 2018 8h11
Objet : [BITX20] BITX40: Qui peut m’aider ? Who can help me ?

>
>

Bonjour
 
Y at'il des OMs francophones sur la liste
J'ai acheté un BITX40 et je n'en suis pas satisfait, j'ai un tac tac pendant la rotation du bouton Fréquence qui est assez pénible.
Merci de me répondre en direct sur mon adresse : f6cxo@...
 
73 Gégé
 


Re: One question only...

Alan de G1FXB
 

Thanks Tom,

I didn't have a problem reading any of your text,
more reading my text back and although I may have thought it, it didn't make it to the written stage.....
  On the subject of direct IQ and no opposite rejection:
"As a virtual SA we are not interested resolving either USB / LSB, (bothsides, if present) of a carrier"
As a virtual SA we are not interested resolving either USB / LSB, (bothsides, if present) we are not interested in demodulating the carrier, merely displaying it's presence and amplitude.



Gordon, and thank you from me, as well for the HF Explorer link.
That in turn reminded me to revisit Red Pitaya Dev Boards after +2 years, it was a greater cost for the sake of only a CW Skimmer project at the time.
However others have taken on brewing  so much around that project, one of it's original apps was a basic SA card......
So that's a fourth solution.


Alan



On 10/08/2018 04:31, Tom, wb6b wrote:
Hi Alan, welcome,

Yes, if you google around you will find instructions on doing the direct sampling mod on dongles that don't do direct sampling, and where to solder the antenna wire. The RTL-SDR dongle from here https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ has the mod built in, with the advantage that they added an RF switch so the your SDR radio software can switch modes. 

I have both the RTL-SDR dongle and a NooElec dongle http://www.nooelec.com/store/sdr/nesdr-smartee-sdr.html that I use with the Ham-It-Up converter. I like both of these dongles. I'm amazed they work as well as they do. Fortunately, I do not have many strong broadcast stations and such nearby; that may help.

Also, in my last post, I switched from referring to the demodulator chit to calling it the decoder chip. I hope that did not cause any undue confusion.

Hi Gordon, the RF Explorer link you posted about looks interesting. I'll look at it further.

Tom, wb6b


Re: BITX40: Qui peut m’aider ? Who can help me ?

f6cxo
 

Bonjour Laurent

Mon Anglais étant inexistant, j'utilise GOOGLE traduction etl'échange est long.

J'essaie de programmer la version 1.28 sur mon BITX40 et il y a des messages d'erreur qui empêchent la programmation.

73 Gégé

 

 

 

 

> Message du 09/08/18 21:15
> De : "DREYFUSS Laurent via Groups.Io" <f4czi@...>
> A : "BITX20@groups.io" <BITX20@groups.io>
> Copie à :
> Objet : Re: [BITX20] BITX40: Qui peut m’aider ? Who can help me ?
>
>
Bonjour Gégé,
 
C'est vrai qu'un peu plus de participation en français serait la bienvenue. Par contre, une réponse directe prive automatiquement les autres personnes intéressées par le sujet d'informations pouvant êtres utiles.

>
73

>
Laurent F8CZI
>
 



De : f6cxo <f6cxo@...>
À : BITX20@groups.io
Envoyé le : Jeudi 9 août 2018 8h11
Objet : [BITX20] BITX40: Qui peut m’aider ? Who can help me ?

>
>

Bonjour
 
Y at'il des OMs francophones sur la liste
J'ai acheté un BITX40 et je n'en suis pas satisfait, j'ai un tac tac pendant la rotation du bouton Fréquence qui est assez pénible.
Merci de me répondre en direct sur mon adresse : f6cxo@...
 
73 Gégé
 


Re: Harmonics measured by Warren. How bad?

Warren Allgyer <allgyer@...>
 

Ashhar

I respectfully disagree with the main point of your premise, to paraphrase: "The uBitx is ok because it has less spurious emissions than are allowed for a commercial amateur transceiver operating at 100 watts or a transceiver/amplifier operating at 1500 watts". There are two things wrong with this premise, 1) Modern commercial transceivers are specified to have emissions at least 50 dB below carrier level; many are specified at 60 dB or more. Such transceivers have spurious emissions far below those of the uBitx even when operated at 100 or 200 watts. 2) Unfortunately that is not how the rules are written or applied by the respective governing bodies. The allowed level of emissions must be 43 dB below carrier level, 50 dB in most countries other than the USA, regardless what that carrier level may be. That may not seem logical but that is the rule that is a condition of our license and that we committed to uphold when we received it.

The compliance of my uBitx with these rules is summarized here:



You have addressed only the recently discovered harmonics issues. And my unit, as you have noted, is not disqualified by excessive harmonics on bands above 17 meters. Unfortunately, on those bands, it is disqualified by the previously discovered "45 MHz minus carrier" spurs.

You say "First: the trouble seems to be more with CW than SSB harmonics. We can reduce the CW level by decreasing the CW drive level."

Perhaps, but I think you will find that the harmonics on CW are far more a function of putting the harmonic rich square wave output of the Si5351 directly into the transmitter signal chain without filtering. The reason the CW versus SSB issue disappears in the high bands is because the circuitry itself acts as a filter "rounding" out the square waves at these higher frequencies. I don't think your proposed drive level change will affect CW harmonics but it is worth a try.

You have written "Second: the alignment as it comes out from HF signals will show far better harmonic suppression than being reported here. For instance, the -38 dbc on 20 meters and -30 db on 40 meters will almost disappear if you balanace it out with the bias on the IRF510s. The factory alignment works like this : First crank up both the IRF510s for 100 ma standing current on each, then tweak one of them to null out the harmonics. It is like balancing out the carrier on diode modulator."

The harmonics causing the problem in my screen shots are odd harmonics; 3rd, 5th, 7th, 9th etc. The alignment procedure you recommend only affects even harmonics due to the cancellation effect of the push-pull PA. It has no effect whatsoever on odd harmonics and, in fact, had been optimized just as you describe before my testing.

You say: "Third: below 14 MHz, the IRF510s are distorting with too much drive. If you back off the drive to adjust to a leve of 7 watts, the harmonics will climb down to be within the spec."

Sorry, but not so for my tests. As noted in my text, all harmonic screenshots were taken with drive reduced to result in a consistent power output for each band of +33 dBm, 2 watts. This was done precisely to avoid overdriving any stage of the transmission chain. At maximum drive, particularly on 80 and 40 meters the harmonics are considerably worse.

Your filter designs and components as supplied are adequate for the PA filtering application. Removed from the board and laid out in a linear fashion with no relays, the filters exhibit well over 55 dB of attenuation at the 3rd harmonic and higher for each band. The primary limiting factor is the strategy of running the input and output of each filter through at least one common relay; lower bands do this with two or all three of the relays. Input to output crosstalk within the relay becomes the first and most substantial contributor to the "blow-by" of harmonics bypassing the filters. The second factor is the "daisy chaining" of the low frequency signals through multiple relays. Finally, a high power PA harmonic filter must have extremely high overall isolation between the input and output of the assembly. The long traces and circuitous routing on the board to connect all of these relays contributes to lack of input/output isolation. When laid out on the board and routed through the relays the filters exhibit on the order of 25 dB attenuation at harmonic frequencies; far too little to be compliant.

The relays per se are not the problem.

It may be possible to make the uBitx compliant with only better PA filter layout: No sharing of relays between filter inputs and outputs, no daisy-chaining of relays, more straightforward PCB layout. However, due to the "45 MHz - carrier" spur issue such filters would need to be BPF rather than LPT. Alternatively, a 4-6 filter assembly, switched in conjunction with the PA filter and placed between the first mixer and the drive chain would likely clean up the signals to the point that the existing filter arrangement may work.

Based on the discussion here and a parallel one on the Facebook uBitx page, I do not believe my results are "sample of one" or the result of a defective unit. That, however, remains a possibility until someone publishes data assembled with similar care to refute them.

I love the concept of uBitx. I want it to work and work well. I sympathize with the pragmatic concept that "it makes less spur power than an high power commercial rig" but that is not the rule. And you can already see the number of people who connect the uBitx to linear amplifiers on the assumption they are starting out with a compliant radio but they are not. 

I cannot, in good conscience, put my unit on the air as it stands. Each amateur radio operator needs to be guided by his or her conscience in this matter. But if the decision is made to go ahead it should be made with the full knowledge that it is a violation to do so.

Thanks for soliciting responses and for listening.

WA8TOD 

Re: One question only...

Tom, wb6b
 

Hi Alan,

Just noticed your point about not needing to resolve which side of the carrier you are on, in the case of using a dongle as a SA. That is a good point. Even if you could see a difference in the energy within the bandwidth the scan is sweeping across the spectrum scanned, it does seem it would not matter and could be compensated for if it did. 

Tom, wb6b

Re: Harmonics measured by Warren. How bad?

Jerry Gaffke
 

I mostly agree.

I'm OK with folks using this rig in those modes where it's maybe 2 or 3 dB off.
If 10dB, not so much.

The goal should be to meet standards on at some point, and to do so
without the aid of a spectrum analyzer or similar while tweaking it. 
I think this will require repeatable gains in some of the amps, the 45mhz IF comes to mind.

On the Bitx40, it was necessary for Allard to drive the modulator pretty hard to unbalance it
sufficiently on all rigs.  Could be we will need a pot at R104 to deal with rig variations.

Curious that Allison's spur at 45mhz - OperatingFreq does not show up in Warren's plots as an issue.

Would be nice to do everything with 2n2222's and 2n3904's,
but I think works and cheap and available from online distributors are the primary criteria.
Not many people have even half the parts for a uBitx in their junkbox.

Will be interesting to see what a few more rigs look like, and exactly
where and how much they are failing to meet spec. 

Jerry, KE7ER


On Thu, Aug 9, 2018 at 10:22 PM, Ashhar Farhan wrote:
Let me put some of the discussions on harmonic and spur purity of ubitx in context.