I believe that phase noise from the si5351 will scale up proportional to the output frequency.
So while phase noise from a 5mhz vco could be fine, it might become more of an issue
with the 45mhz IF of the ubitx. ?Receiving a 30mhz signal would put the vfo at 45+30=75mhz.
So phase noise on 10m with the ubitx that's 15 times worse than the Bitx40 on 40m.
However, several ubitx have been built, and apparently work well.
Jerry
toggle quoted message
Show quoted text
On Mon, Oct 23, 2017 at 04:29 pm, Jerry Gaffke wrote:
Trouble with a 455khz IF makes sense.?
There is a reason Farhan went to a 45mhz IF on the ubitx.
?.....
Phase noise may matter at some point, perhaps with narrow band digital modes like JT65?
|
Re: FS:W8TEE TFT boards and parts
Hi David
I am interested, let me know your Paypal ID and I will pay for it. Thanks.
Sebastian K4BAC
From: N8DAH <Dherron@...>
To: [email protected]
Sent: Monday, October 23, 2017 4:57 PM
Subject: [BITX20] FS:W8TEE TFT boards and parts
I wanted to get this project off the desk as I don't have time to work on it and no cash to get a 2nd bitx for it.
I have 2 x W8TEE boards for the tft display 2x regulators one AD9850 2x encoders 5 x AO3's one mega2560 pro mini (purchased from the same place Jack has gotten his in the past)
?
I am looking to sell the lot 35$ shipped to your door.
?
?Any questions please e-mail me direct
d herron at live dot com
?
73
?? David
????? N8DAH 
|
Trouble with a 455khz IF makes sense.?
There is a reason Farhan went to a 45mhz IF on the ubitx.
Plenty of weird things going on around mixers,?
many of which I am sure will surprise me if I ever get beyond armchair pontificating
and try getting designs of my own working.
I really don't have the tools to look for phase noise or minor mixer products.
But did order an sdrplay after hearing Pavel recommend it a few weeks ago for
inspecting crystal filter shapes. ?Is there software appropriate for measuring phase noise
using the sdrplay? ?Does the sdrplay have a local oscillator with significantlly
less phase noise than?the si5351? ?Also hope to use it as a spectrum analyzer,
hooking it up to a Rasberry Pi 3..
Phase noise may matter at some point, perhaps with narrow band digital modes like JT65?
I assume phase noise would present itself as more random noise when tuning in a weak signal,
though there are other possible causes for that symptom. ?
Many say the bitx40 sounds good, even compared to commercial gear that costs 10 or 20
times as much. ?And the Raduino has always had si5351 code that used a fractional output divider,
first with the Etherkit library and now with the si5351bx routines.
toggle quoted message
Show quoted text
On Mon, Oct 23, 2017 at 03:12 pm, Pavel Milanes Costa wrote:
In deed if you use a high enough IF (as the bitx40 do, in 12 Mhz) all the unwanted mixing are cleaned by simple filtering, but beware if you use a low freq as 455Khz or 500 Khz... those unwanted mixing products will haunt you...
|
Re: FS:W8TEE TFT boards and parts
The parts are currently awaiting payment if he falls through I will update the post?
|
Re: BITX QSO Night, Sunday, October 22, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere
Confirming a good contact with Randy WB5YYM. Thanks for Arkansas! As is generally the case, W1LY was too close in for me to hear.
Lots of other good contacts made while listening, including DX. I worked YU1XA (Serbia) with my 5 watts. He¡¯s a fixture kilowatt station on 40m.
73s All,
Bruce KC1FSZ
|
El 23/10/17 a las 16:53, Jerry Gaffke via Groups.Io escribi¨®: The ARRL Handbook says square waves are better,
though does not say anything about how huge the difference is. We are talking the same language, we are agree on the point that square is better, but not always... I'm just making a little note to the side of the page about a special case as per my experience... Grab your digital copy of the ARRL handbook and keep looking at chapter 10... search for figure 10.22 on page 10.21 just in the next page of your note. Look at the graphic at the bottom of figure 10.22 compare the output from using a sine wave vs square wave, square wave has ALL the harmonics (solid line), the sine one has none (dashed line) Also the output from a sine VFO is 3dB lower than the square one. ;-) I was only saying that if you use the Si5351 as BFO to mix with the IF and grab the audio, and you use a low freq on it (below ~2 Mhz as per my experience, worst on the 500 Khz range) you may get a very noisy audio as those solid lines (harmonics) are very close? each other and will mix again and again inside the mixer/amplifiers and you will get a very noisy reception, full of carriers here and there... On tx there is no problem as the SSB filter wipe them away... In deed if you use a high enough IF (as the bitx40 do, in 12 Mhz) all the unwanted mixing are cleaned by simple filtering, but beware if you use a low freq as 455Khz or 500 Khz... those unwanted mixing products will haunt you... Been there, done that, must filter it if you use a Si5351 for BFO below ~2Mhz. -- 73 CO7WT, Pavel.
|
Re: FS:W8TEE TFT boards and parts
What is pictured is all you get. I did order the screens but both came damaged and I ran out of funds for this project.
|
I haven't tried modelling it, but I wonder if one could employ something similar to the circuit used in a z match tuner for bandpass, especially if you cold come up wits a way to tunexpected the entire frequency rangel without bandswitching. Outboard low pass filters as suggested by Farhan would be a really easy way to go, you may even get away with using one filter for 2 bands if they wereally close enough together (20/17, 17/15, 12/10 ????). I guess you would have to test it to find out. I better order some toroids I guess.
Brent
|
When you build a crystal radio kit at Christmas, isn't that ?a crude "band pass filter" at the front end? ?Just a parallel LC circuit! All of mine always received more than 1 AM station, so their Q was low enough that they responded to more than one frequency.
Sent from my iPhone
toggle quoted message
Show quoted text
Hi Farhan and Jerry,
Thanks for that clarification. Outboard LPF's are certainly one way to go about it. A tune-able BPF is an interesting idea! I wonder if one could use servos to make it automatically adjust to the frequency. Calibration would be required of course, but it's
got me thinking about it. A dual gang air variable could be used. I wonder how that could be done... probably above my head, but surely is possible.
--
Ryan Flowers W7RLF
?
?<--
Learn how to go digital on the BITX40
|
Thanks, all, very cool, learned a lot!!
Sent from my iPhone
On Oct 23, 2017, at 5:07 PM, Karl Heinz Kremer, K5KHK < khk@...> wrote:
toggle quoted message
Show quoted text
Take a look at this video for an explanation why square signals are better for mixers:?
|
Re: FS:W8TEE TFT boards and parts
Are the displays touch screen? Or are there no displays included?
Vince.
toggle quoted message
Show quoted text
On 10/23/2017 04:53 PM, N8DAH wrote: I wanted to get this project off the desk as I don't have time to work
on it and no cash to get a 2nd bitx for it.
I have 2 x W8TEE boards for the tft display 2x regulators one AD9850 2x
encoders 5 x AO3's one mega2560 pro mini (purchased from the same place
Jack has gotten his in the past)
I am looking to sell the lot 35$ shipped to your door.
Any questions please e-mail me direct
d herron at live dot com
73
David
N8DAH
--
Michigan VHF Corp.
|
Hi Farhan and Jerry, Thanks for that clarification. Outboard LPF's are certainly one way to go about it. A tune-able BPF is an interesting idea! I wonder if one could use servos to make it automatically adjust to the frequency. Calibration would be required of course, but it's got me thinking about it. A dual gang air variable could be used. I wonder how that could be done... probably above my head, but surely is possible. -- Ryan Flowers W7RLF
?
?<-- Learn how to go digital on the BITX40
|
I'm going to have a look at the 2430A.
Current setup:
Tek 11402 Scope w/ 11A32 400MHz plugin
Tek P6121 10x probe - 1 meg termination in the scope
No bandwidth limiting
Adafruit si5351 board CLK2 terminated into 51 ohms.
Standalone Nano controlling it.
NOTE: CLK2 is also used for the following measurements.
There is a difference in output between 7.5MHz and 35.5MHz, but only about 15mv rms.
There's a bit of ringing on the square wave but that's probably in my setup.
Ok, with the above setup, at 11.020 MHz:
2ma setting: 190 mv rms.
4ma setting: 380 mv rms.
6ma setting: 560 mv rms.
8ma setting: 735 mv rms.
Vince.
toggle quoted message
Show quoted text
On 10/23/2017 01:50 PM, Vince Vielhaber wrote:
Nope, I don't bandwidth limit that scope (Tek 2430A). I'll do another
measurement tonite with the Tek 11402 and see what it says.
Vince.
Oh, and the si5351 is driving those series schottky diodes through a 6db
attenuator, which cuts the voltage in half.
Maybe you had your scope on some low bandwidth setting or something.
On Mon, Oct 23, 2017 at 10:44 am, Jerry Gaffke wrote:
If so, hard to imagine Farhan would get the ubitx to work at all, as his
first local oscillator is at 45mhz + signal
Apparently works up to a 30mhz signal frequency, so 75mhz from the
si5351.
And it has to drive something like 0.6v into two series schottky diodes
for them to start conducting.
--
Michigan VHF Corp.
|
Take a look at this video for an explanation why square signals are better for mixers:?https://youtu.be/WwJKxvz7qbs
|
Thanks Dave.
I am going to try controlling the PTT through the nano to control the clock better before the PTT off is triggered. So a new nano input from the mic PTT and a new output from the nano to a 2n3904 to switch the PTT line on the board.
I dont have AGC or CW on my rig so less complications.
I have a transistor across the lm386 input that switches to ground when PTT is pressed at the moment and I have no audio pop. I cant remember how I triggered the transistor though so Ill have to work through that and hopefully it will be compatible with this new plan above.
73
Simon VK3ELH
|
The ARRL Handbook says square waves are better,
though does not say anything about how huge the difference is.
My understanding is that the more a diode ring mixer departs from being a perfect switch
driven by a square wave, the greater the intermodulation distortion.
Slowing down the switching edges by driving with a sine wave does not help
in most measures of performance.
The action of an ideal switching mixer is that of doing an analog multiply of the incoming signal
with a square wave, as described in post 22538 (one beyond the post previously cited).
You could break that square wave down into odd harmonics of specific amplitude through
its Fourier expansion ? and multiply those by
the incoming signal to calculate?hard numbers for what comes out of the IF port. ?
No need for any small-signal handwaving.
Jerry
toggle quoted message
Show quoted text
On Mon, Oct 23, 2017 at 01:15 pm, Gordon Gibby wrote:
hence the book's observation that it doesnt make a huge amount of difference.? ??
?
|
FS:W8TEE TFT boards and parts
I wanted to get this project off the desk as I don't have time to work on it and no cash to get a 2nd bitx for it.
I have 2 x W8TEE boards for the tft display 2x regulators one AD9850 2x encoders 5 x AO3's one mega2560 pro mini (purchased from the same place Jack has gotten his in the past)
?
I am looking to sell the lot 35$ shipped to your door.
?
?Any questions please e-mail me direct
d herron at live dot com
?
73
?? David
????? N8DAH
 
|
Glad to hear that this idea is working out for you Simon.
I?am now?on holiday?so unable to play/experiment?for a few weeks, and have not had?chance to load Allard's new release.?
I need to experiment more but I think the PTT sense is not required at all if the mic PTT is connected directly to the Raduino (A0).? For CW I think it is it is not needed, the Raduino keys the transmitter itself via D7?.? A delay from keying to operating the relays will be required in CW also o stop the carrier burst - I have not looked in the code to see if that is implemented, I did do something in my version but cannot look right now.? If the relay?switching or cap charging/discharging can be made faster then that could help reduce the delay.? Not looked at that at all as CW is still a mystery to me.
I did manage to build Farhan's AGC circuit and have tried?connecting the PTT output from the Raduino (output D7) through a diode to charge up the AGC cap and mute the audio on TX.? This unfortunately did not solve the RX-TX pop, and the time constant going from TX-RX was quite long before audio could be heard again.? I injected the 5v between the agc diode and the resistor, so next attempt will be after the resistor to reduce the rise time, as Gary suggested.? Not decided the best approach for reducing the TX-RX decay - options include reducing the bleed resistor, reducing the capacitor value or reducing the voltage the cap ultimately charges to?down from the 5v output by the Raduino D7.? I may add another FET to invert the PTT input from the Mic switch to get the mute going earlier and then try lowering the ?voltage applied to the AGC circuit to reduce the decay time.
This is what its about for me - thinking about a problem, playing, trying things and seeing what does/doesn't work.? Just hurts a bit when the smoke gets let out and some poor component dies, but all part of the learning experience.
Have fun!
Dave M0WID
|
As I pointed out, I'm using my own Nano. No Raduino is used in this.
Vince.
toggle quoted message
Show quoted text
On 10/23/2017 02:25 PM, Michael Hagen wrote: I have made my own version of these. They work fine on a Nano, but
since there is NO Address selection it probably collides if you put it
on Raduino with its SI5351.
The 20 Pin version of the SI5351A has ONE address selection pin, so the
next ones I make with be with the 20 QFN part.
It is over 2 the price and in the QFN package.
Mike, WA6ISP
On 10/23/2017 10:59 AM, Vince Vielhaber wrote:
Not coming off the Raduino, I'm using one of these:
Much simpler but does the same thing. My own Nano connects to it without
the need for a display.
Vince.
thanks. I assume you measured right at the output of the radiuno and not
after the 6db attenuator.
I'm hoping to use this thing as a replacement VFO for some old heathkits
once I learn what THEIR vfo output voltage was.....I'm pretty sure they
were at 2K ohms so I may be able to use a ferrite transformer and step up
voltage through simple impedance matching. It would be really cool to
have the advantages of the digital VFO on my old (and EMP proof)
SB-102!!!!
Gordon
________________________________________
From: [email protected] <[email protected]> on behalf of Vince Vielhaber
<vev@...>
Sent: Monday, October 23, 2017 1:20 PM
To: [email protected]
Subject: Re: [BITX20] Raduino question.
measured where, across what impedance?
thanks for the information!!! Typically my RF measurements are all at 50 ohms, but right now I can't say
for certain that last nite's were. I'll have to double check when I get
home. Also I need to correct something, my initial output was 4ma, not
2ma.
Vince.
--
Michigan VHF Corp.
--
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID "MotDog@..."
Mike@...
--
Michigan VHF Corp.
|
?Again I'm not an expert, but even tho this isn't a linear system, for small signals one might be able to make an approximation of it using the superposition principle.
In other words,? ?that square wave has WITHIN IT the sine wave of the desired frequency, and the diode mixer probably responds (to a first order appxoimation) as:
sine wave LO? x modulation frequency --->? ?sum & difference
2nd harmonic of LO? x moduclation frequency? ---> sume and difference
......
nth harmonic of LO x modulation ferequency --->? sum & difference.....
and then the filter next throws out everything except the desired one......hence the book's observation that it doesnt make a huge amount of difference.? ??
In the long run, it is the tiny tiny changes as a result of interaction between the two frequencies on a non-linear transfer function that accomplishes the mixing.? ?The diode isn't a binary device (1 and 0 only) but instead is a non-linear device with a
transfer function that has infinite steps between? ?0 volts and 1 volt.? ?
(my 2 cents worth)
I think looking at it in the frequency domain may be more instructive than looking at it in the time domain.? ??
gordon
toggle quoted message
Show quoted text
Hmm. ?I guess opinions vary.
In my 2015 edition of the ARRL Handbook, page 10.19, section 10.5.2 for "Switching Mixers",
the discussion about diode ring mixers assumes a square wave for the local oscillator.
The only reference to a sine wave local oscillator in that section is this:
"Normally, the harmonic outputs are so widely removed from the desired output frequency
that they are easily filtered out, so a reversing-switch mixer is just as good as a sine wave
driven analog multiplier for most practical purposes, and usually better for radio purposes,
in terms of dynamic range and noise."
The si5351 is not very well spec'd, but the si5338 of the same famiily is, and those docs suggest?
the phase noise when using fractional values in the output msynth dividers is well under
a factor of two worse than running the part with integer divides on both pll and output msynths. ?
Many in this forum are very happy with their analog vfo, once they've tamed it's tendency to wander.?
That analog vfo would have much worse phase noise than the si5351.
I suspect many of the issues with mixers and birdies and such revolve around poorly terminated mixers,
especially at the if port, and poorly shielded rigs allowing vfo harmonics to crawl into places they should not. ?
On the si5351, I'd be more concerned about crosstalk when using mulltiple outputs than with phase noise. ?
This post from last February: ?
plus a few of the neighboring posts in that thread describe how a diode ring mixer works,
and how a square wave switching an incoming signal can be considered a multiplier. ?
Jerry
On Mon, Oct 23, 2017 at 11:52 am, Pavel Milanes Costa wrote:
I'm not agree, in my experiments I found that driving it with Square Waves is more efficient, but a lot dirtier. ARRL and RSGB Handbooks agree on that, several academic papers on the internet are agree.
|
N8DAH
Brent Seres/ VE3CUS