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Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Alan G4ZFQ
 

I will skip experiments with an tcxo.
Henning

Do not forget you have been given links to cheap TCXOs that have analogue control.
In my experience such a TCXO has been better than my OCXO although I admit I probably gave up to soon with my attempts to optimise it.

73 Alan G4ZFQ


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

mrdynalink <server@...>
 

@Halden: Thank you for telling me your experiences, I will skip experiments with an tcxo. I believe, I already saw your described discrete frequency jumps in the past. Before I tried the U3s I already checked the U02-DDS-Synthesizer. There a 25 MHz txco from Farnell is used. I remember that I was wondering about the asynchronous frequency jumps on 2m-Band ... may be the same problem.

@Glen: Thank you for the hints. Meanwhile I cancelled the plan to use the standard synthesizer and I ordered 2 OCXO for experimenting :-)

@Andy: I`m looking forward to seeing the results of your new 2m U3S ! When I`m ready with my OCXO I will report. Hope this is soon, I'm excited  :-)

73, Henning


Trouble with Blocks on top row of LCD #problem #qcx

s.qrplabs@...
 

Hello,

I'm working on building the QCX Revision 4, and I've got a set of black bars showing up on my LCD.

I've gone through the troubleshooting tips, and the issue seems to be that the processor isn't starting up (or at least not communicating with the LCD.)

I've verified the processor is inserted correctly, correctly oriented, and that the pins are connecting correctly.  I've verified that the processor is getting power.  I've verified that the crystals are oscillating.  I've also spent quite a bit of time just staring at all the soldering connections and verifying that they work.  I've also spent a while testing a bunch of the capacitors just to make sure they're working correctly.

At this point, does anyone have any advice for me?  Thanks!

Chris


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Glen Leinweber
 

"When I put my finger on the crystal I see the frequency jumping for 100Hz or more."

Is this frequency jump from your hot fingers? I'm wondering if it has another source, because your
plot shows a fairly fast change of frequency.
I'm wondering if some local RF fields are re-biasing the oscillator, causing quick drift.
I'd be tempted to try grounding the crystal case. It is currently floating, and can act as an antenna.
And perhaps adding some shielding above/below the Si5351 + crystal. A tin hat & underpants.

It is also possible that local RF fields affect the power supply regulator feeding Si5351. Twist those
Vcc & ground wires together to minimize loop area.


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

M0RON
 

Hi Henning,
I received my 3rd u3s today, this one will be 2m only, one bs170 at 9v pa, OCXO fitted with gps module for calibration. 
I should have it built and oven set in about 4-5 days. I'll see what my U3s shows when txing wspr on 2m.
Andy
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.


Re: QSX External Amp Keying

Hans Summers
 

Hi Nick

QSX contains ALC yes

The Tx/Rx output is a logic level signal to power the amp. It can be active low or active high (configurable). One should not take (or give) more than a few mA. So would need a buffer or relay driver. 

73 Hans G0UPL

On Fri, Nov 23, 2018 at 7:46 AM Nick VK4PP <nickpullen@...> wrote:
Hi Hans
Relay or 12v out? ALC functionality?

I'm building a PA0FRI 2 tube QQE60/40 Linear and the QSX will be driving it with 10w. I am hoping for a solid 200w+ on the other side.

73 Nick.


Re: 5 volt supply QCX #supply

Alan G4ZFQ
 

2. De-soldered regulator,-- Now the lower pad, without the regulator IC installed, shows a short to ground.
Could this have been the reason for only 0.4V?

Check all +5V points for a solder bridge/whisker. Are C37, IC3/4 etc correctly oriented?

73 Alan G4ZFQ


Re: Clock Temp sensors LM36/TMP36 Fahrenheit display #t2 #clock #t1

Ryan NN7M
 

Thanks for working that out. 

Ryan KE7RW 


Re: QSX External Amp Keying

Nick VK4PP
 

Hi Hans
Relay or 12v out? ALC functionality?

I'm building a PA0FRI 2 tube QQE60/40 Linear and the QSX will be driving it with 10w. I am hoping for a solid 200w+ on the other side.

73 Nick.


Re: QSX External Amp Keying

Hans Summers
 

Hi Mike 

Yes!

73 Hans G0UPL 

On Fri, Nov 23, 2018, 07:05 KV4TT - Mike <kv4tt.qsl@... wrote:
Hello I wondered if the new QSX will have an amp keying line to key an external amplifier?
Thanks,
Mike-KV4TT


5 volt supply QCX #supply

joehemus@...
 

QCX  rev4  5 volt power supply.  Two problems:
1. On startup LCD back-light but no data displayed.  13.8v supplied to regulator.  Voltage output at regulator and various points along 5v rail (example GPS plug) measured at 0.4 Volts.  Re-checked soldering.  Removed LCD.  No change.
2. De-soldered regulator, but inadvertently lifted 5V solder pad on the top of the PCB.  The bottom pad was not damaged.  Cleaned up the remains of the upper pad down to the fiberglass.  Now the lower pad, without the regulator IC installed, shows a short to ground.
Sure will appreciate help to get my new QCX into operation.


QSX External Amp Keying

KV4TT - Mike <kv4tt.qsl@...>
 

Hello I wondered if the new QSX will have an amp keying line to key an external amplifier?
Thanks,
Mike-KV4TT


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Alan de G1FXB
 

Alan,

good save.

Two staples no shack should be without, Veroboard and Araldite.... :-)

A.

On 22/11/2018 14:26, Alan G4ZFQ wrote:
I never was a fan of soldering direct to the pads of one of the 'cheap' Si570's in case they tore off under the stress of a 'full sized' component lead and would leave everything floating with a strand from 16/.02 first.
It would make a grown man cry if it was one of the expensive variants....
Alan,

A long time ago I received a couple of "A" grade Si570s after asking for a sample!!
On one of them  when using a thick wire to dead bug it I cracked the ceramic substrate around the corner ground pad. I covered it with epoxy glue and it's carried on working ever since..
Apart from that modern components survive a lot of abuse.

73 Alan G4ZFQ


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

KEN G4APB
 

Hi Henning,
as you have tried all the obvious ‘fixes’, I did wonder if what you are seeing is a characteristic of your receiver. I have seen this effect in high speed data receivers due to the audio coupling capacitors charging at the start of a data bit. Can you get an audio output from earlier on in your receiver, say before any audio amplification?

73 Ken g4apb 


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Alan G4ZFQ
 

I never was a fan of soldering direct to the pads of one of the 'cheap' Si570's in case they tore off under the stress of a 'full sized' component lead and would leave everything floating with a strand from 16/.02 first.
It would make a grown man cry if it was one of the expensive variants....
Alan,

A long time ago I received a couple of "A" grade Si570s after asking for a sample!!
On one of them when using a thick wire to dead bug it I cracked the ceramic substrate around the corner ground pad. I covered it with epoxy glue and it's carried on working ever since..
Apart from that modern components survive a lot of abuse.

73 Alan G4ZFQ


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Alan de G1FXB
 

Thanks Alan,
Missed that one....
Not used on TCXO but in another application I never was a fan of soldering direct to the pads of one of the 'cheap' Si570's in case they tore off under the stress of a 'full sized' component lead and would leave everything floating with a strand from 16/.02 first.
It would make a grown man cry if it was one of the expensive variants....

Cunning & clever, good to see"Traditional" Veroboard is alive an well even in the age of SMD. :-)

Next time the lid is off.......
Alan

On 22/11/2018 11:48, Alan G4ZFQ wrote:
https://ka7oei.blogspot.com/2018/02/better-frequency-stability-for-qrp-labs.html
It's smaller than the Fox alternative, but may be worth consideration if
you can work with the device?
A method of mounting and connecting devices like these.

https://groups.io/g/QRPLabs/message/27233

73 Alan G4ZFQ


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Alan G4ZFQ
 

https://ka7oei.blogspot.com/2018/02/better-frequency-stability-for-qrp-labs.html
It's smaller than the Fox alternative, but may be worth consideration if
you can work with the device?
A method of mounting and connecting devices like these.

https://groups.io/g/QRPLabs/message/27233

73 Alan G4ZFQ


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Alan de G1FXB
 


On 20/11/2018 21:05, mrdynalink wrote:
So ... back from experimenting. What I did:

1.) I connected a very strongl regulated powersupply with thick wires direct to the U3S mainboard. Hmm ... there was no visible change at all. I played with the supply-voltage, reducing the voltage to 4.8V changed the frequency only for 10Hz. But at start of transmission the "chirp" seems to come from "infinity"...

2.) When I put my finger on the crystal I see the frequency jumping for 100Hz or more. It seems to be very temperature-critical. Somewhere I read that it is a good idea to put a heatsink to the crystal to make the temperature-changing lazy. So I soldered a 2 Cent coin direct on the crystal. But again, no influence to the chirp at the beginning of transmission.

3.) Now I tried to measure the 27 MHz Carrier from the crystal. I connected my Perseus antenna-input direct with the 2 Cent coin and I found the crystal oscillating at 27.005 MHz. Then I tuned the Perseus into the wspr window and made a recording with Argo. This was very interesting:


 
During the pause between the transmissions the crystal frequency makes a big jump. But the crystal should oscillate accurate on one fixed frequency! What is the reason for this behaviour ? Currently I have no idea and have to think about it. Possibly somebody else has an idea for the reason ?

However ... I think it`s a good idea to order the oven-controlled version ... not primary for the oven but for the decoupled 27 MHz oscilator.

Correct,

Perhaps if you take the OXCO route as you have documented characteristics for the Si5351 kit at VHF, it would be a useful half way step to repeat the testing with the OCXO
but with the heater unpowered to purely to observe the improvement brought about by alternative Osc circuit.Before employing the heater option.
Alternatively as others have stated the cheap TCXO's generally have a robust output not to be affected by loading changes.
The FOX has being used in the past, if you search the complete forum thread, another device characterised is :-

https://groups.io/g/QRPLabs/topic/28195580#28671
https://ka7oei.blogspot.com/2018/02/better-frequency-stability-for-qrp-labs.html

The page title is for the ProgRock, but in actual fact the improvements are made solely to the Si5351 module and is applicable to all QRP-Labs kits using the Si5351 kit.
It's smaller than the Fox alternative, but may be worth consideration if you can work with the device?


Alan


73, Henning


Re: #synth ref frequency #synth

DC1MAK
 

merci beaucoup Gilles, many thanks Alan,

i knew, ther was something written somewhere....
in the next weeks i'll try different clocks with
my Arduino-based transmitters....
I'll report my experiences....

73 de DC1MAK micha


Re: #synth ref frequency #synth

Alan G4ZFQ
 

This is explain in assembly manual of Si5351A of QRPLabs.
In this module, a
27MHz crystal is used. This frequency is chosen because it is possible to
configure the chip to produce the exact 1.46Hz tone spacing for WSPR, on
any amateur radio band from 2200m (136kHz) to 2m (145MHz).
What we do not know is just how sensitive the WSPR decoder is to frequency accuracy.
I use 26MHz TCXOs and have decoded my 2m transmissions with no problem.
There was some discussion a few months ago about using even a 10MHz reference for the Si5351 but nobody thought to try WSPR using that.
WSPR has to cope with borderline HF propagation, TX and RX drift.
Without knowing the tolerances of the WSPR decoder it is wise to keep as close to the specifications as possible but I suspect the tolerances are wider than many think.

73 Alan G4ZFQ