Date   

Re: FOX TCXO

HF
 

Hi Alan,
Yes, very similar to my observations.  Now that I have the Taitien TCXO installed, I get much more reliable decodes and almost always zero drift reports.  Another thing I observed is that the SNR reported in WSJT-X is now more stable.  I've also noticed that the Taitien's centre frequency drifts a little bit as the ambient temperature varies between 3 and 20 C.  I hope to have a chance to quantify that drift later this week.
Cheers
Halden NR7V


Shack clock contrast adjustment

KI7MWA
 

For overly sensitive contrast adjustment the assembly manual suggests either 220k ohms or a jumper at R4.  Strikes me as a pretty wide difference.  Happens I don't have any 220k resistors, are other values functional? What difference (or differences) will different values make?


Re: Error:Si535A - no clk

Mike
 

Duh, I thought I'd checked everything...

I blew an si5351 and fitted a new one, everything seemed to work, but looking
under my dissection microscope I see a solder bridge.. qrx..

Sorted. I looked and looked with a x10 loupe, and could'nt see any short, but
when you pointed me back to the clock I decided to get out the big bouy.

Nice russian dissection microscopes tend to assist sometimes <vbg>
many thanks Alan.
73, Mike

On 11 Dec 2018 at 14:30, Alan G4ZFQ wrote:

I can see no difference between the two when in the progrock, but unable
to
see whats happening in the VFO because it wont boot...
Mike,

I note the VFO uses Clock 2.
Is that the problem?

73 Alan G4ZFQ



Re: FOX TCXO

freefuel@...
 

Hi Graham, what does the termination do for crosstalk between the outputs? 

-Justin N2TOH


Re: FOX TCXO

Alan G4ZFQ
 

Graham,

However, one thing I did notice which seemed to make a big difference in
stability and this is termination of the synthesizer output.
Those shots were taken when the Synth module was installed in the U3S, I guess unknown load value? But constant.

You may find this document of interest:
https://www.sitime.com/api/gated/AN10028-Probing-Oscillator-Output.pdf
My "probe" was a small length of wire coiled under my custom U3S box which has the display at the top and back removed. So it was about 25mm behind the synth module. No measurements apart from frequency.

73 Alan G4ZFQ


Re: FOX TCXO

Alan G4ZFQ
 

I also use the Fox TCXO in all my QRP-Labs and own projects... > What equipment did you use> for this measurements ?
To monitor the 27MHz I used a FCDPro+ SDR and HDSDR. Any reasonably stable RX with Argo, SpecLab or even HDSDR set to mono input will do the same thing.
My GPS reference is simple, cheap, shown here https://sites.google.com/site/g4zfqradio/u-blox_neo-6-7 a u-Blox GPS which has a configurable output up to about 15MHz. For 27MHz I use the 3rd harmonic of 9MHz, maybe +/- a few Hz.

73 Alan G4ZFQ


Re: Error:Si535A - no clk

Alan G4ZFQ
 

I can see no difference between the two when in the progrock, but unable to
see whats happening in the VFO because it wont boot...
Mike,

I note the VFO uses Clock 2.
Is that the problem?

73 Alan G4ZFQ


Re: FOX TCXO

Graham, VE3GTC
 

Yes, I have seen this behaviour too.

I have been messing about with the QRP-Labs si5351a synthesizer board to
see if I could get a precise (i.e. steady, unchanging) signal from it,
actual frequency (accuracy) was less important.

the design works quite well whether GPS disciplined or not. Using a
standard crystal or oscillator it is (of course) subject to
environmental variations.

I tried the FOXX924B-27.000 TCXO as noted by Hans in the documentation
and as tried by others. Works OK but I did notice the "discrete
dithering" as you have observed. Couple that with GPS disciplining and
the actual frequency output jumped around in response. It seemed as
though the occasional discrete jump in the TCXO and the GPS trying to
correct where "fighting" each other for a bit. I can see where at VHF
this would be an issue.

However, one thing I did notice which seemed to make a big difference in
stability and this is termination of the synthesizer output.

I was testing using a qrp-labs si5351a synthesizer and prog-rock
monitoring the desired frequency on a frequency locked Icom R75
receiver. My "antenna" was just a simple short piece of wire
conveniently soldered to the synthesizer board output. this was all set
up on the workbench at the far end of the basement. I noticed that the
frequency I was measuring on the receiver was varying every time I was
near the workbench. It would change quickly - up, down, whatever, and
return to near normal after I left it alone. It was a bit of a "light
bulb" moment when it occurred to me that there was enough stray
capacitance and inductance in my body that was being coupled into the
short piece of wire antenna and that was effecting the
synthesizer/progrock to the point that it was causing these changes.

A bit of research on the subject and I found some reference to others
experiencing cross talk between the outputs of the si5351a and within
the documentation there are comments regarding the configuration of the
output drive of the si5351a and output impedance.

I am uncertain at what level Hans' software sets the si5351a to but I
would guess likely at 8ma level which (I think) corresponds to an
impedance of about 85 ohms.

In any case, I found that if I terminated the output of the synthesizer
module ( I used 50 ohms as it was handy) then the output become much
more stable and of course current consumed by the modules also increased.

You may find this document of interest:

https://www.sitime.com/api/gated/AN10028-Probing-Oscillator-Output.pdf

A quick search for similar documents on the subject will find others.

Those are simple qualitative observations.

I found a couple of much higher spec'ed TCXO 0.5 PPM which I have yet
to try. I have put the progrock and si5351a's aside for the time being.

cheers, Graham ve3gtc

On 12/11/2018, "Alan G4ZFQ" <alan4alan@gmail.com> wrote:

A couple of shots showing the FOX TCXO looking at the 27MHz output.
One shows the first 2 minutes of warmup from initial switch-on.
The other shows it warm but dithering, up/down a Hz or so, seemingly
having no hysteresis. (This was part of my WSPR on 2m tests, made 2m
WSPR useless.)

Just the one sample, has anyone else seen this?

73 Alan G4ZFQ





Re: FOX TCXO

DC1MAK
 

Hi Alan,
I also use the Fox TCXO in all my QRP-Labs and own projects...
What equipment did you use 
for this measurements ?

This evening i will have a look on the output of my 
synths...

Several times i thought about a 27MHz source disciplined by 10 MHz ( GPS or Rubidium)

I'll post my experiences this evening

73 de micha DC1MAK


Re: QCX not working

Norman Miller
 

Good news Ron.
I discovered that the pins that go into the bottom of the LCD were not making contact. When I moved the LCD around a little then the display would come up as it should. I am trying to find the best way to keep the pins where they need to be. Have you heard of the problem before.


On Wed, Dec 5, 2018 at 12:12 PM, Ronald Taylor
<wa7gil@...> wrote:
 If the earlier voltage checks I mentioned are now good (5v out of the regulator, then you need to check voltage on pin 3 of the LCD. This is the third pin from the left. It will vary from 0-5 v as you adjust R47. 

If that’s good then there’s a different problem and (with power off) you will need to do continuity checks from each pinnof the LCD to the corresponding pin of the processor, looking for an open circuit. Also use the ohm meter to check for shorts between adjacent pins of the LCD. 

You are in to some basic troubleshooting here and I highly recommend you read Hans’ excellent troubleshooting guide at www.qrp-labs.com/QCX/qcxtrouble.html

Good luck

Ron



On Wed, Dec 5, 2018 at 09:48 Norman Miller via Groups.Io <kn4gsl=yahoo.com@groups.io> wrote:
Ok I connected the power to the radio this morning. Nothing showed on the display. I adjusted R47 but nothing. Do you have any more ideas. Thanks


On Tue, Dec 4, 2018 at 4:32 PM, Ronald Taylor
<wa7gil@...> wrote:
Outstanding. Hope everything else works out ok on it. 

Ron

On Tue, Dec 4, 2018 at 14:31 Norman Miller via Groups.Io <kn4gsl=yahoo.com@groups.io> wrote:
Ok got power now I had the power lines reversed. 


On Tue, Dec 4, 2018 at 2:44 PM, Ronald Taylor
<wa7gil@...> wrote:
If you’re seeing 12 volts on all three legs of the regulator it means the center lead (common) isn’t grounded to the rest of the circuit for some reason. Set your meter to ohms (with Radio power turned off) and check for continuity (zero ohms) from the center leg of IC11 to the negative power connector terminal. If this is a high resistance check closely to see why the center pin isn’t grounded. Could be solder joint or that pad isn’t grounded (very unlikely). 

Don’t power the radio back up till you get to the bottom of this. If you really have 12 volts on the output pin of IC11 then it’s possible other stuff got damaged. 

Ron

On Tue, Dec 4, 2018 at 12:34 Norman Miller via Groups.Io <kn4gsl=yahoo.com@groups.io> wrote:

Thanks for the fast reply. I took the neg lead of my meter and put it on the neg terminal of the power connector. I took the pos lead of my meter and touched each leg of the IC11 I got 12. ? volts on each leg.
Not such if I an touching the wrong thing with the neg lead.
On Tuesday, December 4, 2018, 10:29:11 AM EST, Ronald Taylor <wa7gil@...> wrote:


Norman, the manual says to first check to make sure you installed R48 and then check to see if the connectors between the display and main board are correct. Next you should check for 5 volts from the voltage regulator. That’s the large three terminalndevice to the left of the display and the 5 volt output should be on the right hand leg as viewed from the direction of the display. If no 5 v then check the left hand leg of the regulator to look for your 12 v input. If that isn’t there make sure you oriented the polarity protection diode the right way. If it’s correct then check for 12 v on both sides of that diode. If it’s the right way and only see voltage on one end then it’s bad. If no voltage on either end then check your power connections. Also one thing to check is the polarity of the 12 v supply. If it’s backwards then the diode is doing it’s job protecting the circuits. The positive should be in the lower screw of the input terminal strip. 

Hope that helps. 

Ron 

On Tue, Dec 4, 2018 at 07:57 Alan G4ZFQ <alan4alan@...> wrote:
> I just completed my qcx kit it looks great. I connected the power to it
> but cannot get any light to come on the display. I have checked and I
> have power on the board but don't know what to check next. Need some advice.

The manual gives some voltage checks, where does it go wrong?

73 Alan G4ZFQ






Re: OCXO

freefuel@...
 

Hi Jer, will do the kit is still sitting on my bench untouched. however the plan is simple, I'm going to omit the original crystal and everything between it and the Si5351a. I will most likely stand the part up on it's side against the heater transistors. from that point on after I verify it works, I'll snap some photos and box it up. 

-Justin N2TOH


Re: QSX tcvr built-in Spectrum Analyzer

Hans Summers
 

It IS a directional coupler. Power and SWR measurement built in.

73 Hans G0UPL

On Tue, Dec 11, 2018, 16:22 gerrykav via Groups.Io <gerrykav=yahoo.co.uk@groups.io wrote:
Yes, that's what it looks like alright. You can see pads for the primaries on each side.
/ Gerry


Re: QSX tcvr built-in Spectrum Analyzer

gerrykav <gerrykav@...>
 

Yes, that's what it looks like alright. You can see pads for the primaries on each side.
/ Gerry


Re: QSX tcvr built-in Spectrum Analyzer

Ben Bangerter, K0IKR
 

I think I spot the makings of a directional coupler in one of the photos of the main QSX board that Hans has put out - the binocular core transformer highlighted here.  Perhaps it is part of a power-leveling circuit as well?  Fun to speculate!


Error:Si535A - no clk

Mike
 

Confused...
I'm getting Error:Si535A - no clk displayed on a QRPlabs VFO version s1.03

What is confusing me is this...

I have two Synth boards, both of them work correctly in a Progrock,
the I2C levels appear correct, clk0 and clk1 are outputting a signal at about
the right level and frequency.

When I swap each of the synth boards into the VFO board, one boots correctly
and functions, the other gives the Error:Si535A - no clk report.

I can see no difference between the two when in the progrock, but unable to
see whats happening in the VFO because it wont boot...

Any ideas appreciated...
73 Mike


Re: QSX tcvr built-in Spectrum Analyzer

gerrykav <gerrykav@...>
 

I guess you have thought of this already, Hans, but it seems that you are only a directional coupler & a few other bits away from having an antenna analyser built in too.
/ Gerry


FOX TCXO

Alan G4ZFQ
 

A couple of shots showing the FOX TCXO looking at the 27MHz output.
One shows the first 2 minutes of warmup from initial switch-on.
The other shows it warm but dithering, up/down a Hz or so, seemingly having no hysteresis. (This was part of my WSPR on 2m tests, made 2m WSPR useless.)

Just the one sample, has anyone else seen this?

73 Alan G4ZFQ


Re: VFO/SigGen questions

Alan G4ZFQ
 

Hans Summers wrote:
The 27MHz reference oscillator measurement is made to 0.01Hz resolution.
I was looking through some screenshots I made recently, checking the performance of my U3S on 2m.
The one I show here was taken when the U3S was calibrating. It indicates that my 27MHz crystal is pulled about 1Hz high during the calibration period. (The continuous straight line is my GPS-derived marker signal.)
I wonder if anyone else has done a test like this?
I have not checked my VFO but I see no reason why the same thing would happen if I put that same synth module in that. (All my other synth modules have a TCXO which are not pulled.)

The WSPR frequency changes also pull the 27MHz very slightly, not really visible at 27MHz but enough to give a few Hz +/- variation on 144MHz WSPR.

73 Alan G4ZFQ


Re: Wiring of 5W amp to U3S

Hans Summers
 

Hi Curt

Apologies for the delay. 

The diagram on page 3 of AN004 is correct *except* that the pins labeled in orange "RF Out (filtered)" are not there now, as you mention. Now they are moved to the left of the board, just above the switch S2. Everything else is correct. 

So you feed the U3S PA along the green wire from U3S board to the 5W PA board. Then you send the 5W RF output back from the 5W PA board, to the U3S board, along the Orange wire as shown. Then take the final RF output from the pins labelled "RF Out (filtered)" - it is just that these have been moved to near S2 on the U3S PCB current revision. (Note: you plug the LPF into the U3S as usual, and make sure C5 is removed). 

I'm sorry about the confusion, it is hard to keep all the documents in sync with all the different PCB revisions and firmware revisions. 

So in summary: almost everything about AN004 page 3's diagram is correct, it is just the pads labelled "RF" and "GND" on the PCB, and labelled in orange "RF Out (filtered)" on the diagram, have been moved to the left of the board, above S2. 

73 Hans G0UPL

On Mon, Dec 10, 2018 at 2:28 PM M0RON <eustace.andy@...> wrote:
Hi Curt, 
Yes agree that it needs updating. 
I think that if you were to take the rf from the rf out pins to the amp you'd then have to place a low pass filter after the amp.
If c5 is removed and rf from the amp fed back to the u3s it then uses the filter in position 0. The schematic doesn't make this clear but I think that this is what happens. 
Good luck 
Andy.
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.


Re: VFO/SigGen questions

Hans Summers
 

Hi Paul

In addition to the (excellent) other answers to your question... 

The 27MHz reference oscillator measurement is made to 0.01Hz resolution. 

But the calculation of the Si5351A registers inherently contains its own built-in inaccuracies and this is what limits it to 0.1ppm (actually it is more like 0.03ppm in practice). This could be improved (if there were more hours in a day). But this is the state of the firmware currently. 

You are also correct that the error scales with frequency. But this includes both the error of the 27MHz ref clock, and the inaccuracy of the calculation. 

73 Hans G0UPL



On Mon, Dec 10, 2018 at 1:42 PM N1BUG <paul@...> wrote:
I am trying to determine whether the VFO/SigGen would be a
worthwhile upgrade to several crystal oscillators and one inferior
TCXO in my station. I have a few questions.

Has anyone measured accuracy or short and long term frequency
stability? The operating manual says it updates the 27 MHz reference
frequency in .01 Hz steps but doesn't explicitly state how often
(every second?). App Note 006 says the accuracy is 0.1 PPM which is
worse than I would expect if the reference is updated in such small
steps. Maybe we are talking about two different things... accuracy
vs stability/drift?

Am I correct in assuming any error of the 27 MHz reference is
divided down if the output frequency is lower? Eg. if the 27 MHz
reference changes by 1 Hz, an output signal at 2.7 MHz would change
by 0.1 Hz?

Is there any issue with setting the output to 27 000 000?

73,
Paul N1BUG