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QDX modes

CALEB_ELI_3
 

Hi there, this is KJ7YYM, I am a bit confused as to what exactly the QDX is capable of.? I have a list here of modes I am most likely to use.? Can someone tell me which of these it can and can not do?? Thanks.

RTTY
Clover
DominoEX
Thor
FSQ
WSQ
IFKP
Olivia
MT63
VARA
ARDOP
JS8
SSTV
 

Standard digi modes software like WSJT-X and JS8Call works fine with QDX,
 

???


On Thu, Nov 18, 2021, 3:36 PM N3MNT <bob@...> wrote:
Standard digi modes software like WSJT-X and JS8Call works fine with QDX,

 


It should be able to do any sequential FSK mode. Throb is out because it sends concurrent tones. PSK31, Clover, etc are phase-shift modes, so no good.?

I know the answer for a few of these. A lot of them are going to be hard to find in the wild. I'm having a hard enough looking for Olivia signals to test on.?

RTTY?YES
Clover?NO - PSK
DominoEX??YES
Thor
FSQ
WSQ
IFKP
Olivia??YES
MT63 NO?
VARA
ARDOP
JS8??YES
SSTV

¨CBrent WT4U
CALEB_ELI_3
 

Thank you all for your help.? That is too bad about Clover, it can send executable files.? By the way, I forgot to mention I meant the low speed FSK VARA, not the fasterr PSK VARA.? Thanks again.??

73 DE KJ7YYM
 

¿ªÔÆÌåÓý

Caleb,

the trouble with Clover is that there is no obvious official published technical specification (it exists somewhere, but there is no clear pointer). The ARRL page at? (and other sources) suggest that Clover modulation always includes either or both of PSK (phase shift keying) or AM (amplitude modulation), generally as trellis modulation, otherwise known as QAM (quadrature amplitude modulation).

In short, Clover seems never to be FSK (frequency shift keying) only. Thus it's not suitable for the QDX, which requires an FSK only, single carrier only, modulation scheme. And, AFAIK, there is no free software modem so a modem would cost far more than a QDX.

In relation to VARA, even FSK VARA starts with 14 independent FSK carriers (lowest data rate), so it's out for the QDX.

HTH, 73, Stay Safe,

Robin, G8DQX

On 19/11/2021 02:14, CALEB_ELI_3 via groups.io wrote:

Thank you all for your help.? That is too bad about Clover, it can send executable files.? By the way, I forgot to mention I meant the low speed FSK VARA, not the fasterr PSK VARA.? Thanks again.??

73 DE KJ7YYM
 

Does anyone know if (and under what conditions) the QDX output frequency changes are phase continuous? Is this guaranteed by the si5351 switching method it uses? What are the limits of this behavior?

I hope I'm expressing this question correctly... It seems important to understanding what modes can be generated without creating spurious signals outside the signal's expected passband...

thanks in advance,

M
 

Hello Mario?

Yes the output is phase continuous by design. The Si5351A strategy uses fractional multiplier on the PLL feedback, not the output multisynth dividers which are at a fixed even integer. The PLL also has a finite, relaticely low, loop bandwidth which in other words means it has a slow slip to the next configured frequency.?

Furthermore programs such as WSJT-X and JS8Call implement a gradual shift from one frequency to the next. Since QDX is capable of measuring single audio cycles and updating the Si5351A it follows the shift from one frequency to the next as a somewhat gentle slide. Please refer to the theoretical section of the manual for screenshots.

So it is both phase continuous as well as implementing gradual frequency changes; consequently it has a clean output, on JT mode variants and FS8 mode. If you want to look at some faster modes than you can optimize the performance accordingly by changing the cycle averaging parameters in the QDX configuration.?

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


-------- Original message --------
From: Mario Vano <mvano@...>
Date: Fri, Nov 19, 2021, 6:46 PM
To: [email protected]
Subject: Re: [QRPLabs] QDX modes
Does anyone know if (and under what conditions) the QDX output frequency changes are phase continuous? Is this guaranteed by the si5351 switching method it uses? What are the limits of this behavior?

I hope I'm expressing this question correctly... It seems important to understanding what modes can be generated without creating spurious signals outside the signal's expected passband...

thanks in advance,

M

 

Brilliant, I know one can use the 5351 that way, but wasn't sure you were actually being careful to stick to the modes that did so. That makes it a little easier to understand what modes will work and which won't.

Thanks again for sharing...

M
 

For fast modes such as RTTY, does anyone know how well the QDX keeps up? What does the transmitted signal look like on another receiver? (I.e. bandwidth usage, and is it still as decodable as when sent using fldigi + a traditional SSB transmitter?)

(I guess I will find out if/when I get my hands on a QDX, but perhaps someone has already tested this.)


73 de SM6VNO Anders
 

Hello Anders

I have not tried RTTY but I suggest having a thorough read of the manual.?

The configuration of the tone decoding?algorithm?is optimized for slower modes such as FT8 etc. It currently makes around 100 measurements per second. For RTTY it would probably be desirable to reduce the frequency measurement precision in favour?of more measurements/frequency adjustments per second. These settings are in the Configuration terminal application. This is all described in the manual.?

73 Hans G0UPL

On Tue, Dec 21, 2021 at 11:31 PM Anders Gavare <gavare@...> wrote:
For fast modes such as RTTY, does anyone know how well the QDX keeps up? What does the transmitted signal look like on another receiver? (I.e. bandwidth usage, and is it still as decodable as when sent using fldigi + a traditional SSB transmitter?)

(I guess I will find out if/when I get my hands on a QDX, but perhaps someone has already tested this.)


73 de SM6VNO Anders

 

I realise that this is a 3 year old thread but ......
?
How about 150bd AX.25 for HF APRS? I'm thinking about giving this a try. Also Robust Packet (look it up).
?
Mark, NI2O

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