Topics

Problems with u3S waveform FSKCW

m0bmn
 

Hi All

Please have a look at the waveform picture from my U3S, I have change synths from standard to TXCO but just the same, what do you think will cause this, I have 7805 reg feeding the tx , 12v on the PA , I  have changed the 7805, its got  0.1uf and 470uf caps on its output and 0.1uf and 100uF on its input, the main 12v supply is from a 30amp Yaesu supply and it also powers the 40m U3S which is nice and clean (the problem one is on 30m)

Tried it at 10mW to 2 Watts and its just the same , using a dummy load and so not overloading the rx.

Any ideas???

73 Paul M0BMN

 

 

Sent from Mail for Windows 10

 

John Canfield
 

I'm not going to be much help since I'm in the dummy club but what do you get with a constant key down? I assume the power is fluctuating or is that some kind of spurious spike or noise? Sometimes I'll get all excited when I see something weird on the scope and more often than not the problem is me - how I set up the test.
--
John, WB5THT

Al Holt
 

I believe Hans has written/mentioned you can expect slight stepping with a TCXO. I think you'll need to use the OCXO module of QRP Labs to get a really steady trace. They're not hard to build, just a bit time consuming building the 'oven.'

Threes & Fours!

--Al
WD4AH

Dean Smith
 

Hi, Paul! Again.
You'll find this gets worse as frequency increases!
Refered to as jitter. On/off of heater in tcxo as it tries to stabilise. This will lead to non decode for modes such as wspr.if you check out fox data on these devices, you'll see why OXCO's are probably better placed for this application.
Dean.

Paul WB6CXC
 

Where in the circuit are you probing to get this waveform?  What are your Voltage and timebase settings?
--
Paul Elliott - WB6CXC

M0RON
 

Hi Paul, 
Do you get the same issue with both synths? Std and tcxo?
I have 3 working OCXO 's, would you like to borrow one to try?
Andy.
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.

M0RON
 

A stab in the dark,
Is the psu powering both u3s at the same time? If so, what happens if you only run the steppy u3s on its own? 
Andy

--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.

m0bmn
 

Hi

The waveform is from the receiver, I was txing into a dummy load at this time.

Cheers

Paul

 

 

From: <QRPLabs@groups.io> on behalf of <paul@...>
Reply-To: <QRPLabs@groups.io>
Date: Wednesday, 27 February 2019 at 19:45
To: <QRPLabs@groups.io>
Subject: Re: [QRPLabs] Problems with u3S waveform FSKCW

 

Where in the circuit are you probing to get this waveform?  What are your Voltage and timebase settings?
--
Paul Elliott - WB6CXC