Re: Spurs and Harmonics - Definitions and Measurements
Bruce
Mark adds some clarity.? Those measurements you describe relate to 'unintended' radiation apart from the antenna connector path - yes we often experience this in our homes and workplaces.? In the uBITX we are mostly interested in what comes from the antenna connector - sometimes called conducted spurious.? As we are world-wide, we might find that other nation's requirements may be similar to those here in the US - some may be more stringent perhaps.?
As Farhan points out, the regulation is in dBc (relative power) versus the real-world phenomena relating to receiving absolute signal strength in dBm.? But the regulations may not allow our argument.? [I also asked my local fellow club members about those speed limit signs, and how often we might exceed those by just a little ... but they weren't interested in my analogy!].?
Regulations tend to be even tougher in VHF and UHF, due in part to criticality of emissions in that spectrum.?
Practically, it is good practice to work our uBITX transceivers into our own nation's requirements.? We are collectively challenged as few of us possess spectrum analyzers.? A recipe for modifications that provides a little performance margin would be nice.? We don't yet that I know of have technical consensus on the solution.? I suggest we not major on one particular board being the measure of solution as there is some variation in levels across the population.? I like adding relays for the harmonic issue as I think it should provide conservative margin - I am not sure of the best solution for 45 MHz related IF spurious.?
Curt
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Ordered my v5 ubitx today, case delivery tomorrow!
Boy am I excited!? My case from amateurradiokits.in is almost here, and I was able to order my V5 ubitx today!?
Kelly K5AID?
Sent from my Verizon, Samsung Galaxy smartphone
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A circuit board contains 3 added relays that connect to the input side of the 4 low pass filters.? Following assembly of this board, the user must cut a few traces and then install short pieces of thin coax to make the connection.? A pc board was designed by a list member, only the artwork is available.? Our club made a batch of these boards and kitted the needed parts - a few of us have them installed into our uBITX, but I only know of one unit being measured so far - it passed with margin.? My v4 needs over 10 dB improvement in the harmonics on some bands - I don't know if change to the alternate relay will achieve this or not.?
Now if this solution would be preferred - then 'all' that is needed is for someone(s) to kit and sell it maybe.? Clarifying, this fix only address one source of spurious.? Curt
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Re: ubitx v4 - distortion in received audio
On Mon, Mar 11, 2019, at 6:57 PM, Mark - N7EKU wrote:
Hi Ramakrishnan,
Not sure if your audio problem is related to the audio amp section, but if it is this link shows a fix that shouldn't be too hard to do:
Make sure you read Allison's post number 53356 in that link for adjusting the operating point of Q71.
Thanks so much Mark. I also spoke to Raj. I will try the modification tomorrow and report back.
73
Ramakrishnan VU3RDD
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That's excellent! I didn't do anything further. I removed my hmi upload so it could be tested before too many people downloaded it.
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Re: Spurs and Harmonics - Definitions and Measurements
Bruce, Your point is well noted. I made a similar argument. It ia true that a -40 dbc at 10 watts is less than -48 dbc at 100 watts.? However, this is largely a challenge of compliance. The FCC mandates that all spurious emissions should be at least -43 dbc. So, that's what we shoot for. This figure is meant only for radios manufactured after 2005. Your vintage gear need not be fixed. - f
On Mon 11 Mar, 2019, 7:14 PM BruceN, < k4tql@...> wrote: I've seen many messages relating to the cures for spurs and harmonics for the V3, V4 and V5 units.? Right now there are nearly 1000 messages dealing with this topic.? But, I'm confused.? And, what exactly are the limits for emission of spurs and harmonics?? I've researched the FCC regs and it's like reading a foreign language to me.? But what I did glean is that the FCC tests in, basically, an anechoic (to RF) chamber and report the results, depending on frequency range, in microvolts.
What I see in the messages is that folks are reporting spur and harmonic levels in dB.? Now, db is a ratio so what are those db values compared to?? To the level of the primary signal?? Are they measuring spur and harmonic suppression?? Again, compared to what??
If spurs and harmonics readings are to be given as a particular level, they should be reported as dBm, not dB.? dBm is also a ratio but it is compared to a fixed level of 1 milliwatt.? The emitted power given in those units would be the same if measured on a transmitter running 10 watts as a transmitter running 100 watts.
However, if the readings are given in dB, it is representing suppression.? A -50 dB reading on a 10 watt transmitter will have an actual radiated power far less than a -50 dB reading on a 100 watt transmitter.? So, if we're measuring and reporting dB on the uBitx, maybe those reported levels are not so bad as folks think.? The radiated power level would be far less than other signals out there.? Easily seen on a scope with high gain but maybe not readable a mile away or even 3 feet away.
If you are measuring actual output power of the spurs and harmonics, report your readings in dBm.? And if that is the units being used, the uBitx might need some help.
So which is it?
My nickel (2 cents inflated).
Bruce, K4TQL
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Re: Spurs and Harmonics - Definitions and Measurements
Is is really such gibber? You seem to have a good understanding of dB.? Here's the text on the specific levels: ¡ì97.307???Emission standards.
...
(d) For transmitters installed after January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission. For transmitters installed on or before January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must not exceed 50 mW and must be at least 40 dB below the mean power of the fundamental emission. For a transmitter of mean power less than 5 W installed on or before January 1, 2003, the attenuation must be at least 30 dB. A transmitter built before April 15, 1977, or first marketed before January 1, 1978, is exempt from this requirement.
Seems pretty clear at least for US FCC regulations.? I'm not sure about other countries.
I think most reporting Spectrum Analyzer results here are talking about dB down from the fundamental.
73,
Mark.
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Spurs and Harmonics - Definitions and Measurements
I've seen many messages relating to the cures for spurs and harmonics for the V3, V4 and V5 units.? Right now there are nearly 1000 messages dealing with this topic.? But, I'm confused.? And, what exactly are the limits for emission of spurs and harmonics?? I've researched the FCC regs and it's like reading a foreign language to me.? But what I did glean is that the FCC tests in, basically, an anechoic (to RF) chamber and report the results, depending on frequency range, in microvolts.
What I see in the messages is that folks are reporting spur and harmonic levels in dB.? Now, db is a ratio so what are those db values compared to?? To the level of the primary signal?? Are they measuring spur and harmonic suppression?? Again, compared to what??
If spurs and harmonics readings are to be given as a particular level, they should be reported as dBm, not dB.? dBm is also a ratio but it is compared to a fixed level of 1 milliwatt.? The emitted power given in those units would be the same if measured on a transmitter running 10 watts as a transmitter running 100 watts.
However, if the readings are given in dB, it is representing suppression.? A -50 dB reading on a 10 watt transmitter will have an actual radiated power far less than a -50 dB reading on a 100 watt transmitter.? So, if we're measuring and reporting dB on the uBitx, maybe those reported levels are not so bad as folks think.? The radiated power level would be far less than other signals out there.? Easily seen on a scope with high gain but maybe not readable a mile away or even 3 feet away.
If you are measuring actual output power of the spurs and harmonics, report your readings in dBm.? And if that is the units being used, the uBitx might need some help.
So which is it?
My nickel (2 cents inflated).
Bruce, K4TQL
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I have had 2 of the original volume controls with similar problems. The contact pin rivets had intermittent connections to the resistance substrate. They were going open. I changed to 10K audio taper controls that I had and the problem never reoccurred. Noises and unexplained distortions disappeared.
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Hi Curt,
Can you elaborate on the "three relays on a daughter card" fix? I don't need a kit - I'll make my own!
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Re: ubitx v4 - distortion in received audio
Hi Ramakrishnan, Not sure if your audio problem is related to the audio amp section, but if it is this link shows a fix that shouldn't be too hard to do: /g/BITX20/topic/22892553#53357Make sure you read Allison's post number 53356 in that link for adjusting the operating point of Q71. 73, Mark.
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Re: ubitx v4 - distortion in received audio
On Mon, Mar 11, 2019, at 6:40 PM, Ramakrishnan Muthukrishnan wrote:
I have been using my uBitx (v4) mostly for receiving until now as I was
lacking a good antenna. I observe a couple of problems.
1. Calibration is off by ~1200 Hz (down). I believe that is corrected
by getting into the calibration menu and tuning at 10MHz with another
receiver.
2. More seriously, the received audio is severely distorted. It also
feels like the audio is saturated at both low and high volume levels..
I also have a 50uV test signal generator at 7040 which I connected to the antenna input. That signal *didn't* sound too distorted when I listened to it. I don't have any other test equipment to poke at the signals.. -- Ramakrishnan VU3RDD
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ubitx v4 - distortion in received audio
Hello,
I have been using my uBitx (v4) mostly for receiving until now as I was lacking a good antenna. I observe a couple of problems.
1. Calibration is off by ~1200 Hz (down). I believe that is corrected by getting into the calibration menu and tuning at 10MHz with another receiver.
2. More seriously, the received audio is severely distorted. It also feels like the audio is saturated at both low and high volume levels..
I will search the mailing list archive for any past instances of such reports and remedies..
73
--
Ramakrishnan VU3RDD
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Re: AGC Pre-Oders are in and built!
That is exactly what I wanted. Very clean install job to boot thank you very much!
--
Tim Keller - KE2GKB
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Mike
I suggest that more, clearer data is needed before recommending a particular spurious fix.? The Axicom relays may work if a board does not require a huge improvement - I think this may be why some are not seeing compliance with this solution.? The alternative solution using 3 relays on a daughter board is actually easier for many builders since it has no need to remove relays from the board - but problem is that no one is sourcing it as a kit.? On the 45 MHz fix, I am not sure that replacing two coils is adequate in itself.? We honestly need more data.? Our own local club has a large group build - we can contribute data when we have it on v4.? I don't want the community having a false hope on any particular cure - and also want the community to understand that a sufficient fix is possible.?
Curt
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Sam, et al
I'm sure it still needs something; here's the full 3.5 screen with manual freq entry numbers where they belong and a READ button on the "Mem->VFO" page that should work -
Ted
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Re: AGC Pre-Oders are in and built!
Here is a picture of the completed install of the AGC board on my V5 board if that helps:
toggle quoted message
Show quoted text
On Mar 10, 2019, at 9:44 PM, KE2GKB via Groups.Io < tkeller@...> wrote: This is amazing news!? If I could be bold enough to ask for a top down picture ala the build instructions just for our archives would that be a pain?
--
Tim Keller - KE2GKB
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Sam,
I took the 15 seconds to hook up my S-meter and the display works just fine with booming signals.? There's plenty of travel across the meter.
Some of the digits in the frequency manual entry screen (touch freq readout on main screen & it changes to band selection/number inputs) are in the wrong place but that's easily fixed on my end.? Have you corrected or worked on anything else since Saturday?
73,
Ted
K3RTA
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Thank you for your work, Mike! Your website has been a great resource for me. I'm glad that you have recovered and I hope you continue to do well! Now I know who to call if I need an enforcer.
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Re: Abandoning my uBitx Ver 3
Thanks Hans for the clarifications. I look forward receiving the QSX! Yesterday I 'sold' a uBitx on the air! It happened that the ham I was talking to (and he was using a Yaesu 9000... ) was so favorably impressed of my modulation he asked me all the details of the uBitx and the HFSignals to buy it directly from India. I hope I will 'sell' on the air a QSX too!
Il 11/mar/2019 09:41, "Hans Summers" < hans.summers@...> ha scritto:
> Will the new QSX be sold in assembled boards??
The 10W HF Linear PA kit is a module of the QSX and is all through-hole see ?
The rest of the QSX boards are pre-assembled SMD. However you need to assemble the buttons, connectors, rotary encoders, and the toroids, and a few other things. There is a built-in inductance meter which is used to check the toroids' inductance before installation.?
So... while QSX is a KIT not a ready-assembled unit, it is not a difficult kit. The number of components to install is relatively small. In particular, all controls are board-mounted so there is no wiring.?
All details
73 Hans G0UPL
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Ramakrishnan Muthukrishnan
Don, ND6T
Ted