Re: the cause for the spurs, found!
Will any of these mods be incorporated into uBitx v4 or even a new version soon?
--
72 and God bless
KD4EPG
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Re: PSK31 ghosts below my signal
Raj, Diane, and the group:? I got a better picture and annotated the signals.? You also asked if I could TX without any audio. So I just hit the PTT with no voice and got a picture. I can see a what I think is a carrier. But I must defer to experts! I've tried to both insert and attach pictures. Thank you!!!    ?
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Re: the cause for the spurs, found!
allison,
i tried with just a regular 2n2222a in place of the 2n3904 (as per your recommedation). instead of the 220 ohm collector load, i used a bifilar transformern with the center tap going to the final mixer. here are the results : (even with the 2n2222a, the performance is acceptable)
On Sun, 4 Nov 2018, 02:47 ajparent1/KB1GMX < kb1gmx@... wrote: Great you found the likely cause of the 2IF spur.
Now why is the 45mhz IF distorting?
Two things, it needs to be clean to at least -6 or so DBM and how much gain is needed to
get to that from the ouput of the 45mhz crystal filter.
I'd suggest starting with transistors that actually have performance at 45mhz.
Allison
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Re: the cause for the spurs, found!
i used a two section LPF, with a corner freq of 36 mhz. 47pf, 300nh, 100pf, 300nh, 47pf. the lpf had to be mounted away from the mixer to be clean. i dont know why.
- f
Which corner frequency for the LPF solution should be used, 50Mhz?
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Re: the cause for the spurs, found!
Will this new discovery require any work in the areas that Allisons power flatten mod provides? changing the 6 3904¡¯s and other related parts. Reason I am asking is I am about to do that mod (easy version) as I have all the parts but if any work in that area needs to be done for addressing these spurs maybe Ill wait to see what solutions are available.?
My guess is one thing shouldn¡¯t have to do with the other and the replacing the 3904¡¯s with 2n2222A should be a good thing anyway.?
Joe
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On Nov 3, 2018, at 6:28 PM, Glenn < glennp@...> wrote:
Allison, a Mini-circuits "PHA-1" might do the trick. I don't have any though.
I don't know how you would get on with it switching direction, back to the Rx side in the Bi-Amp arrangement. Somebody here was experimenting with MMIC bi-amp though but not seen any outcome.
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Re: Si5351 correction question
All three local oscillators into the uBitx that determine the operating frequency
are sourced by the si5351.
And the clocks out of the si5351 are strict ratios of the 25mhz reference frequency
So any error in the 25mhz reference clock will be exactly proportional to the error in your displayed operating frequency.
Assuming the firmware was done correctly.
Example:
When tuning to the rig to 14.0mhz, you find that you are receiving a signal at 14.001 mhz.
Then the 25mhz reference must be at 25.0*14.001/14 = 25.001786 mhz?
That's a 1e6 * 200hz/14000000hz = 14.3 ppm difference.? ?(where 1e6=1,000,000, to convert a ratio to parts-per-million)
Makes me wonder how much of a temperature change is involved here.
Mark had previously reported a roughly 1ppm drift in his Adafruit si5351 board.?
Jerry
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On Sat, Nov 3, 2018 at 04:33 PM, K5ESS wrote:
FWIW when I operate 20 meter FT8 with my uBitx the WSJT-X waterfall display clearly shows about a 200 Hz upward drift for the first 10 to 12 minutes after I power it on. I don't know how that would translate to the drift in the 25 MHz crystal reference.
Mike
K5ESS
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Re: Poor mans spectrum analyzer
#ubitx
Here are some other softwares you can try.
If you have a sdrplay
Joe
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On Nov 3, 2018, at 7:51 PM, Joe Puma < kd2nfc@...> wrote:
I¡¯ve used my 100 watt radio next to a receive antenna for a rtl-sdr. I have fried am/fm filters and the sv1afn upconverter (a few times) but never the dongle. I have locked them up on the usb bus and had to unplug them to reset but that¡¯s about it. You will overload the dongle with an antenna going outside but without anything plugged in it might make it deaf for a ubitx with outside antenna and you in the house. A indoor whip seems doable or a piece of wire.?
I could see you using it as a comparative measurement tool. I¡¯ve used a rtl-sdr to look at characteristics of a filter with a cheap eBay noise source or using a directional coupler to measure swr of antennas. I¡¯m still an infant out here but I¡¯ve played with sdr¡¯s for a while. Baby toys for beginners I guess lol?
Joe I don't know the circuit of the hackRF, but I wouldn't use any antenna connected to the SDR. You could fry its frontend unless it has some protection (I.e. Back to back diodes) at the antenna input. You just see a lot of overloading of your receiver. Having a 8bits ADC the dynamic range is similar to the RTL stick, 48db, so you need to attenuate a lot at least removing the antenna.
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Re: Poor mans spectrum analyzer
#ubitx
I¡¯ve used my 100 watt radio next to a receive antenna for a rtl-sdr. I have fried am/fm filters and the sv1afn upconverter (a few times) but never the dongle. I have locked them up on the usb bus and had to unplug them to reset but that¡¯s about it. You will overload the dongle with an antenna going outside but without anything plugged in it might make it deaf for a ubitx with outside antenna and you in the house. A indoor whip seems doable or a piece of wire.?
I could see you using it as a comparative measurement tool. I¡¯ve used a rtl-sdr to look at characteristics of a filter with a cheap eBay noise source or using a directional coupler to measure swr of antennas. I¡¯m still an infant out here but I¡¯ve played with sdr¡¯s for a while. Baby toys for beginners I guess lol?
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On Nov 3, 2018, at 5:45 PM, iz oos < and2oosiz2@...> wrote: I don't know the circuit of the hackRF, but I wouldn't use any antenna connected to the SDR. You could fry its frontend unless it has some protection (I.e. Back to back diodes) at the antenna input. You just see a lot of overloading of your receiver. Having a 8bits ADC the dynamic range is similar to the RTL stick, 48db, so you need to attenuate a lot at least removing the antenna.
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Re: Poor mans spectrum analyzer
#ubitx
Yep, this keeps coming up in different forms. I agree you need to attenuate your receiver because of overloading the receiver. You are showing a common overload image on a SDR receiver. With my SDR I have a strong signal from my BITX 40 without an antenna on the SDR at all. I haven't tried to see how well I can accurately test the signal that way, but I would think a dummy load on the TX, and no antenna on the RX might be the easiest way to get a better picture of your emissions being tested in the same room. And don't use what ever you are doing for more power either, go barefoot.
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Re: Si5351 correction question
FWIW when I operate 20 meter FT8 with my uBitx the WSJT-X waterfall display clearly shows about a 200 Hz upward drift for the first 10 to 12 minutes after I power it on. I don't know how that would translate to the drift in the 25 MHz crystal reference.
Mike
K5ESS
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Mark Pilant Sent: Friday, November 2, 2018 4:46 PM To: [email protected]Subject: [BITX20] 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: Poor mans spectrum analyzer
#ubitx
Agreed on the front end of the hackRF - this one has already been repaired by me as a friend gave it to me and said, it's deaf - if you can get it going again, it's yours as I have got a new one!
They are renowned for frying the pre-amp chip if it is activated and then a strong nearby signal is fired up close to it and that's what I had to replace (the pre-amp chip) to get it running again.
Apparently, Hams are often keying a handheld too close to it :-(
I used it with a short 1ft (30cm) whip and low gain settings in the spec-an software/hackRF, that's the best way to run it, low gains and increase as needed.
Without any antenna connected, I only saw the main signal at low levels.
The free spec-an s/ware for the hackRF is here, in Linux and Windows flavours (scroll down to the 'Downloads' section)...
I didn't need to run Zadig in my Windows 7 64bit machine as the hackRF installed in Windows automatically.
If you have a cheap RTL-SDR dongle and hack it for HF/use a converter, you can find spectrum analyser software for them as well.
Nigel.
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Re: uBitX CW Sidetone Volume
Further research reveals that this is some audio pop error that is fixed when TX is on, but when someone wants to practice morse, there's that anoying pop again.
Reading through the forum, I found that some suggest that audio pop from TX/RX switching comes from charging mic preamp/turning off receive circuit and vice versa.
But, during TX off mode, receive circuit is always on and mic preamp is always off, but there is that audio pop again.
This time, pop comes from CLK#0 and CW_KEY Raduino pins.
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Re: the cause for the spurs, found!
Allison, a Mini-circuits "PHA-1" might do the trick. I don't have any though.
I don't know how you would get on with it switching direction, back to the Rx side in the Bi-Amp arrangement. Somebody here was experimenting with MMIC bi-amp though but not seen any outcome.
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Re: the cause for the spurs, found!
Right now the 45MHz amp has a gain of about 17dB at 45Mhz and is 3.3dB down at 90Mhz.
Total current draw in my proto build is 32mA.?? With? 3.1mA ? in the 1st emitter follower and 13.3mA? in the 2nd.
Maybe a high P1dB MMIC could be used to replace that section at the cost of current draw, Tx only.
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Re: Poor mans spectrum analyzer
#ubitx
Hey Nigel, what free Spec. Analyzer do you?have?
73 Ken VA3ABN
I don't know the circuit of the hackRF, but I wouldn't use any antenna connected to the SDR. You could fry its frontend unless it has some protection (I.e. Back to back diodes) at the antenna input. You just see a lot of overloading of your receiver. Having a 8bits ADC the dynamic range is similar to the RTL stick, 48db, so you need to attenuate a lot at least removing the antenna.
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Re: the cause for the spurs, found!
Glen.
Yes that the problem.? Or it could be that the two emitter followers are not following...
Hint that circuit at 12Mhz works ok, at 45mhz no so much.? ?Compound amplifiers
without feedback tend to have issues. and Q21/22 are outside the feedback.
And, HP8640B.... right tool for the task.
Allison
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Re: the cause for the spurs, found!
Allison, for -6dBm output level? also means the current in the amp needs to be increased also for better liniarity.
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On Sun, Nov 4, 2018 at 08:17 AM, ajparent1/KB1GMX wrote:
Great you found the likely cause of the 2IF spur.
Now why is the 45mhz IF distorting?
Two things, it needs to be clean to at least -6 or so DBM and how much gain is needed to
get to that from the ouput of the 45mhz crystal filter.
I'd suggest starting with transistors that actually have performance at 45mhz.
Allison
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Re: Poor mans spectrum analyzer
#ubitx
I don't know the circuit of the hackRF, but I wouldn't use any antenna connected to the SDR. You could fry its frontend unless it has some protection (I.e. Back to back diodes) at the antenna input. You just see a lot of overloading of your receiver. Having a 8bits ADC the dynamic range is similar to the RTL stick, 48db, so you need to attenuate a lot at least removing the antenna.
Il 03/nov/2018 18:53, "Nigel G4ZAL" < nigel@...> ha scritto: I have no sophisticated bench test gear so I used my hackRF and the free Spectrum Analyzer software to 'look' at what my uBitx was transmitting whilst on FT8 on 7.074MHz and the result is quite disappointing although not unexpected.
uBitx was on an EFHW for 40M and the hackRF was on a short whip antenna.
I have some Axicom relays and shielded SMD inductors for L5/7 and will compare results after swapping out the bits and see if I can 'clean up my act' !
Nigel
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Re: the cause for the spurs, found!
Harmonics of the HP8640b are of the order of -50dB at output of the gen upto ~+10dbm..
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On Sat, Nov 3, 2018 at 09:43 PM, Henning Weddig wrote:
Glenn,
pleas keep in mind to check the output of Your signal generator, mostly the ahrmonics are in the same range i.e. about -30 dBc to the main cyarrier. So to make sure You do not make false measurements, place a low pass fitler between the output of Your sig gen and DUT.
Henning
Am 03.11.2018 um 10:33 schrieb Glenn:
Not much change really Raj, I used 39k.
At -10dBm input, there is a slight improvement by maybe 2-3dB
At -20 & -30dBm in, virtually same result.
I wonder if a notch could be added for the 2nd Harmonic..... Did you do any sums on the 3rd harmonic? It may also contribute.
glenn
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Re: the cause for the spurs, found!
Great you found the likely cause of the 2IF spur.
Now why is the 45mhz IF distorting?
Two things, it needs to be clean to at least -6 or so DBM and how much gain is needed to
get to that from the ouput of the 45mhz crystal filter.
I'd suggest starting with transistors that actually have performance at 45mhz.
Allison
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