Topics

U3S not getting decodes #u3s


Brian Lewis
 

I’m working on my 2nd U3S, my first one runs flawlessly but I’m getting no spots on WSPR net from my latest U3S.  My transceiver will receive and computer will decode my signals but I’ve had NO spots on WSPR net ever From this latest unit.  Here’s what WSJT Graph looks like, bottom one is 6M and top one is 20M.  Anyone have any ideas?


Mike Besemer - WM4B
 

What are your dial frequencies?

 

Are others getting spots on 6 meters?  (I assume 20 is active…)

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Brian Lewis
Sent: Thursday, May 7, 2020 3:33 PM
To: QRPLabs@groups.io
Subject: [QRPLabs] U3S not getting decodes #u3s

 

I’m working on my 2nd U3S, my first one runs flawlessly but I’m getting no spots on WSPR net from my latest U3S.  My transceiver will receive and computer will decode my signals but I’ve had NO spots on WSPR net ever From this latest unit.  Here’s what WSJT Graph looks like, bottom one is 6M and top one is 20M.  Anyone have any ideas?


ajparent1/KB1GMX
 

what are you using for an antenna.

Also 6M is line of sight if there is no propagation.
And has been mostly for a while.  Also the curved lines suggest poor
frequency  stability.  I"d add without propagation to help 6M
even at 100W is maybe a 100 mile band and that's with 5 element
beam well up.  are there any receiving stations in a 20-50 mile
range?

 Allison
-------------------------------
Please reply on list so we can share.
No direct email, it goes to bit bucket due address harvesting in groups.IO


KEN G4APB
 

Hi Brian,
from your wspr waterfall it shows you have massive frequency shift at the start of transmission. This will prevent any of your transmissions from being decoded. For 6m I found I had to use the qrplabs OCXO to get sufficient stability.

regards
Ken G4APB


James Anderson
 

Hello Brian. 

I would 2nd what Ken has just said. 

The 6m waterfall has huge drift. I use the OCXO to prevent this. 

I can get Zero drift on most TX periods but occasionally. Park mode utilised etc. 
Can you receive your own signal to check for drift?
I also use Argo to see a better interpretation of my signal as it happens. 

It’s as we all know an unpredictable band and also the output power of my 2nd U3S struggles a bit on output power. Very low but perfect to drive the10w linear.
This U3S is an early version.

I’m working on the 10w linear to give it a bit more Oomph but even then I’m not expecting any miracles. 


All the best with it. James. 


Hans Summers
 

See also App Note AN001 http://qrp-labs.com/appnotes on the topic of reducing drift. This can make it usable on 6m even without the OCXO. 

73 Hans G0UPL
http://qrp-labs.com

On Fri, May 8, 2020 at 10:01 AM James Anderson <james21170@...> wrote:

Hello Brian. 

I would 2nd what Ken has just said. 

The 6m waterfall has huge drift. I use the OCXO to prevent this. 

I can get Zero drift on most TX periods but occasionally. Park mode utilised etc. 
Can you receive your own signal to check for drift?
I also use Argo to see a better interpretation of my signal as it happens. 

It’s as we all know an unpredictable band and also the output power of my 2nd U3S struggles a bit on output power. Very low but perfect to drive the10w linear.
This U3S is an early version.

I’m working on the 10w linear to give it a bit more Oomph but even then I’m not expecting any miracles. 


All the best with it. James. 


Allan Nelsson
 

The reason for the curved lines is instability. My original U3, ran with reasonable stability at 30 metres, but after upgrading to the U3S with relay board and LP filters for multiple bands, it went wrong. My intention was to run with successive switching between more bands including  6 metres, but despite many attempts with modifications, foam insulation, cooling and calibration I couldn’t make it work. It's too unstable. So in the future I decided to run WSPR with the Rfzero (www.RFzero.net), which is rock stable. And fortunately the fine QRPlabs filter board can be re-used. :-)

73, Allan


Alan G4ZFQ
 

but despite many attempts with modifications, foam insulation, cooling and calibration I couldn’t make it work. It's too unstable.
Allan,

All my attempts have shown reasonable stability at least as far as HF without any real effort.
Some, like you, have said they have not got it stable.
My reckoning therefore is that there is something that is preventing stability. I'd try changing the crystal, maybe some of those are more sensitive to temperature changes than others.
Drift was a common problem in the early days when the U3 used a DDS but I do not see many posts about unstable Si5351s on HF. Yes, above 30MHz may be more of a problem, I do not know.

73 Alan G4ZFQ


Brian Lewis
 

Thanks for the replies. I showed the 6M graph because it is the worst of the 6 bands. The 20M graph looks jagged compared to my other functioning U3S.  I know I won’t get spots on 6M because of propagation but I would certainly expect some on 20, 30, 40, 80 or 160? 


Allan Nelsson
 

Alan,
 
Maybe the 27 MHz crystal is poor, I don’t know. The picture from Brian shows about 50 Hz drift on 6 m. Or 1 Hz per MHz. Scaled to 10 m it would be 28 Hz and 2 Hz at 160 m which is close to the max permissible drift in WSJT-X as far as I know. So drift on HF is a problem too. Many others have had stability problems, though I know that many do not have such big problems as Brian. I got my 3S running reasonably at 30 or 40 metres, but not quite stable. Higher up, things went wrong. It was impossible for me to make it run steady with successive switching between multiple bands even with calibration in between. I tried all good advice, modifications etc.+ ultra stable PS and so on. So at the end I gave up. But it's spring time - and the sun is shining (in daytime). :-)