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the cause for the spurs, found!
the 45 mhz if amplifier is distorting and producing a second harmonic at 90 mhz. this mixes with the local oscillator to produce a spur at 90 mhz - local oscillator. here is how it happens : the spur moves down as you tune up. when the radio is tuned to 28 mhz, the spur is at 17 mhz. when the ubitx is tuned to 28.150 mhz, the spur is on 16.850 mhz.? at 28 mhz, the local oscillator? is at 73 mhz. there is a signal X such that : X - local oscillator = 17 mhz local oscillator is 73Mhz. X - 73 = 17, X must be 90 MHz. after checking the spur on a number of frequencies between 15 MHz and 30 MHz, it was confirmed that the above formula works consistently to predict the spur.? what is th cure? there are three solutions 1. decrease the distortion of the if amp by modifying or replacing the IF amp (the tx side at least) 2. add a low pass or bandpass filter between the final mixer and the if amp. 3. move to 60 mhz or 70 mhz IF insteead of 45 mhz. a double or triple bandpass should do it. this is a result of joint investigation between Raj and I. - f |
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Tone on Nextion LCD Dimming
A relative and I have both purchased the uBitx boards and upgraded to the CED firmware with a Nextion diplay (he has a 3.5" enhanced and I have a 2.4" enhanced).? Both exhibit a tone when the LCD is dimmed below 92.? We have tried adding capacitors to the 5v line to the Nextion display, as well as on the 12v general supply.? Nothing seems to remove the tone. Testing on the audio output at the high end of the volume control reveals aprox 300 hertz signal that goes away when fully dimmed or full bright.? I have tried probing the 5vdc line to the display, and cannot find any signal there. The only thing that has worked so far has been to use a separate 5 vdc supply for the display. Any thoughts on what could be causing the tone?? Our current guess is that the dimming is done by chopping the supply to the LED back light.? But if this were the cause the filtering on the supply line should at least reduce the sound. ?Seems like over kill to add another regulator to solve the tone issue. Thanks for any suggestion that you might provide. Evan AC9TU |
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Re: Ubitx5 ?
Tim....some one has to tell the truth. There much BS talked here..... On Sat, 3 Nov 2018 2:08 pm Timothy Fidler <engstr@... wrote: Watch it Roger, they will ban you from the site and then you won't get to hear about Rev 5 and the 50 percent off coupon that AF is going to give out to disgruntled purchasers of V3 and V4 boards. !!!? I heard that from a reliable source I can't name.... |
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Re: Ubitx5 ?
I don't agree.....this rig will work to some extent and I have used it for QSOs on 80-40- and 20 metres in CW SSB FT8? and WSPR.? But the software calibration to get it working correctly is an impossible mission unless you are prepared to tolerate always being off frequency. The drive must be kept very low unless you want to radiate spurious RF. I reckon it is good for about 3 watts. There is just not enough information from the factory.? I have wasted too many hours on this. It may be relatively inexpensive, but I did expect it to live up to the statements about what it could deliver. I certainly wouldn't recommend it to a friend, an enemy maybe. 73 Roger ZL2RX |
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Re: Si5351 correction question
Hi Bill.
Did you run in upper sideband and the other in lower sideband?This is a bare Si5351 board being controlled by an Arduino. This is the environment in which the calibration sketch expects to execute. If I set the correction constant, I get the correct frequency at the Si5351 CLK2 for the ubitx. I'm just surprised I had to use two different values. I wonder if it could be related to how long the board had been powered on. 73 - Mark N1VQW |
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Re: Cursed?
I don't know how much this helps, but your description of when it died reminded me very strongly of a problem I found years ago.? A customer had equipment that kept going crazy and failing and couldn't figure it out.? I went in and fixed the machine (component fried).? An employee started using it while I was talking with the owner.? While he was working, another employee plugged in a hand plasma cutter to the same outlet that the machine was plugged into, and as soon as he fired it off, the machine went crazy again.? They couldn't understand it, until I was able to show them that it was putting over a thousand volts of noise into the control - eventually scrambling the computer (it was random when it failed).? They hadn't told me about the plasma before... indeed, it was put away until they decided to use it and didn't realize their plasma needed to be on a completely different circuit.
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Strong RF fields near pins can do just as you described, especially pins that aren't terminated or shielded, on computers (including Arduino units)? - even fry them.? I wonder if you've got a situation where some portion of your TX circuitry is loosing the ground connection, or a rf voltage-based short (yes, I've seen them - a low voltage signal wouldn't short, but as soon as higher voltage hit the component - shorted out, then cleared as the voltage went down).? Those could cause the high current but low RF out.? There are other things that also can do that - parasitic loops and so on. Anyway, good luck with it, if you decide to pound on it a little more!? (GRIN!) Bob N4FBZ On 10/31/18 5:17 PM, Woody wrote:
Original thread was "RX Trouble". ? Sort of a rant here... |
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Re: Ubitx5 ?
Dennis
If you already have a ubitx, its issues can be addressed. Honestly my K2 has more mods than this ubitx needs. The spurs can be fixed. I would rather see an affordable mod kit to service the vast number of ops who already have a ubitx versus a rush to a new version. As for transmit audio, mine exceeds expectation in making contacts. The QSX mentioned will be an alternate multiband rig from qrplabs. Not open source but thus far firmware upgrades have been free on existing products. Its a traditional kit requiring board assembly. The ham community around the world is well served by these rigs. Based upon measurements of my v4 ubitx the spurs are much more significant on upper HF. I clearly don't recommend running a Tx amplifier with an uncorrected ubitx. It does make sense to work toward fixing the rig. 73 curt |
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Re: Si5351 correction question
Hi,
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Did you run in upper sideband and the other in lower sideband? I think that would make a difference. The instructions I have specify doing that calibration with the radio in upper sideband. 73, Bill KU8H On 11/02/2018 05:45 PM, Mark Pilant wrote:
I have finally got my "Franken" uBitx to the point where it is receiving --
bark less - wag more |
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Does anyone use the "Rig" Split operation in WSJT-X for FT8?? I have the KD8CEC v1.1 firmware.? When I have rig split control enabled the frequency increases by 1kHz every transmit cycle.? For instance, when I start out on 20m band I will start out listening at 14.074MHz, when I enable transmit frequency goes up to 14.075, then receive stays at 14.075 for the next receive period.? Next cycle again, frequency increases 1kHz to 14.076 and stays there for 1 receive period and the cycle repeats forever.
Is this a bug with either WSJT-X or the v1.1 firmware? Or do I have my settings messed up on the uBitx?? The "Fake It" setting seems to work as expected.? During transmit it raises and lowers frequency as needed during transmit and then it is set back to 14.074. Thanks, K2BWF |
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Si5351 correction question
I have finally got my "Franken" uBitx to the point where it is receiving
signals; at least from my HP 8642A signal generator. But, there is something strange going on, and I am wondering if anyone else has seen the same strangeness. When I originally ran the si5351 calibration program, everything looked great and I have up with a correction number of 15380. The 10 MHz was measured by my HP 53131A counter referenced to a GPSDO. Fast forward to a little more testing, and I discovered signals I had been receiving were no longer where they once were. Running the calibration program again, with the same Adafruit Si5351 board, I arrived at a correction number of 14210. So my question is: has anyone else seen the same Si5351 use different correction factors to generate the same output frequency? Really scratching my head over this one. 73 - Mark N1VQW |
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Re: Ubitx5 ?
¿ªÔÆÌåÓýDennis
Ashhar is not very forthcoming about plans!? It would be nice to see the v4 boards getting the fixes we know about that work ... like substituting relays to reduce harmonics and a fix for the spurs using SMD components.? None of these fixes would necessitate a new v5 board. I suspect a v5 board would first require identifying the cause of some of the other issues ... i.e. a fix for IMD issues in the bi-di stages, or addressing the issues with carrier leakage, etc. Mike ZL1AXG ubitx.net On 2/11/18 3:17 AM, Dennis Yancey wrote: are there any plans in place for a v5 uBitx?
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Re: my uBitx Power
Joe Puma
¿ªÔÆÌåÓýI do have a device I can use to probe. But max rf voyage is 3v. ?I would have to use resistors with a little trick Jeffery here in the group taught me. I suppose I can try that route and see what it reads.?Joe On Nov 2, 2018, at 12:34 PM, iz oos <and2oosiz2@...> wrote:
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Re: Harmonics and Relay Replacement
Rob Bleumer
Hi all.
I was looking for the specs of the L5 and L7 replacement. I cannot find the exact yellow ones on the internet. The NLT on comkey are not there. They have NLV type. Is this a typo?? Please your source for me and some other builders in my club. We found the relays.But are looking for this parts. Rob PA0RBL |
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