RE: [digitalradio] Sub Channel DQPSK

[Rud Merriam]

Thanks, John.
 
I was thinking of posting a message directed at California operators to see
what their experience was going over the pole to Europe. Your VE-land
experience provides the same information.
 
It is interesting sorting out the anecdotal reports, including yours, the
theory / studies, and the realities.


Rud Merriam K5RUD
ARES AEC Montgomery County, TX 
http://TheHamNetwork.net <http://thehamnetwork.net/>  

-Original Message-
From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On
Behalf Of John Bradley
Sent: Saturday, October 27, 2007 8:45 AM
To: digitalradio@yahoogroups.com
Subject: RE: [digitalradio] Sub Channel DQPSK



For what it's worth Rud, PSK31 appears much more susceptible to phase
distortion that wider modes such as MFSK and OLIVIA.

 

Here, we are just over 50 degrees north latitude and have many more
occasions to experience the 

Northern "flutter" from the aurora. This phase distortion knocks out PSK31
pretty fast. Also makes SSB ops

Sound like Donald Duck

 

There are times when this will show up on relatively short hops (less than
500km) on 80 and 40 M

 

John

VE5MU

 

Would the phase distortion that can corrupt a PSK signal occur the same on a
M-PSK signal? 

If the phase distortion affects all the sub channels then doing differential
PSK among the sub channels would work where symbol to symbol DxPSK would not
work.


Rud Merriam K5RUD
ARES AEC Montgomery County, TX 
 <http://TheHamNetwork.net> http://TheHamNetwork.net 



 

Re: [digitalradio] Sub Channel DQPSK

[Jose A. Amador]

Of course it is. PSK31 goes raw, while MFSK and Olivia have FEC added.
So, stand a better chance of being decoded correctly.

When nature starts stirring the gas above, all it reflects (refracts) 
suffers the same effect as it had passed thru the house of mirrors, 
making giants look like dwarfs and tiny thin people look like King Kong 
for an instant, and then, become the contrary, and so on.

No wonder SSB becomes Donald Duck squared...

73,

Jose, CO2JA



John Bradley wrote:

> For what it’s worth Rud, PSK31 appears much more susceptible to phase 
> distortion that wider modes such as MFSK and OLIVIA.
> 
> Here, we are just over 50 degrees north latitude and have many more 
> occasions to experience the Northern “flutter” from the aurora. 
 > This phase distortion knocks out PSK31 pretty fast.
 > Also makes SSB ops sound like Donald Duck……..
> 
> There are times when this will show up on relatively short hops (less 
> than 500km) on 80 and 40 M
> 
> John
> 
> VE5MU



__

Participe en Universidad 2008.
11 al 15 de febrero del 2008.
Palacio de las Convenciones, Ciudad de la Habana, Cuba
http://www.universidad2008.cu


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RE: [digitalradio] Sub Channel DQPSK

[John Bradley]

For what it's worth Rud, PSK31 appears much more susceptible to phase
distortion that wider modes such as MFSK and OLIVIA.

 

Here, we are just over 50 degrees north latitude and have many more
occasions to experience the 

Northern "flutter" from the aurora. This phase distortion knocks out PSK31
pretty fast. Also makes SSB ops

Sound like Donald Duck

 

There are times when this will show up on relatively short hops (less than
500km) on 80 and 40 M

 

John

VE5MU

 

Would the phase distortion that can corrupt a PSK signal occur the same on a
M-PSK signal? 

If the phase distortion affects all the sub channels then doing differential
PSK among the sub channels would work where symbol to symbol DxPSK would not
work.

  
Rud Merriam K5RUD
ARES AEC Montgomery County, TX 
  http://TheHamNetwork.net 

 

Re: [digitalradio] Sub Channel DQPSK

[Jose A. Amador]

Rud,

You can see the variations in the ionosphere as a phase modulator 
embedded in the channel. So, it will phase modulate whatever you attempt 
to get thru it. Actually, it has a phase modulator embedded for each 
arriving path.

With differential encoding, and signalling speed higher than the medium 
imposed alterations (the phase modulators in the ionosphere due to its 
varying height), you stand a better chance of detecting the changes 
before the original signal has been much modified by the non stationary 
channel. The kind of stuff the Watterson channel model describes with 
its multiple taps and modulators on each tap. What somehow does not fit 
with its restrictions is that the channel parameters may vary even more 
wildly, as delays are not neither equal between each other, as a "well 
behaved model" would induce to think, nor constant, and the "modulators" 
on each tap dances a dance of its own. Something quite complex for a 
mathemathical model to follow, indeed.

The graphic image I keep in my mind is that the ionosphere behaves just 
like boiling water, with a turbulent water-air boundary. Of course, it 
behaves somehow like boiling water in "slow motion". Then, I visualize 
the unstable refraction height as something quite alike to the water- 
air boundary of boiling water.

Some time ago, I began playing with Spectran, making observations of 
offset tuned short wave AM stations with a stable SSB radio. It was 
interesting to see the multiple doppler shifted carrier "threads" 
arriving, as a sort of random dance, sometimes, accompanied by selective 
fading of the threads. Certainly, something very messy to follow and 
demodulate by a data detector.

I have also been watching the multiple windows available with DREAM 
while receiving DRM stations, which can show quite a bit about how the 
channel is behaving. Reading QEX Jan/Feb 2007 page 19 is a good starting 
point.

All that is what makes the challenges even more interesting.


73,

Jose, CO2JA

---

Rud Merriam wrote:

> Would the phase distortion that can corrupt a PSK signal occur the same 
> on a M-PSK signal?



>  
> *Rud Merriam K5RUD*
> ARES AEC Montgomery County, TX
> ///__//_http://TheHamNetwork.net_/


__

Participe en Universidad 2008.
11 al 15 de febrero del 2008.
Palacio de las Convenciones, Ciudad de la Habana, Cuba
http://www.universidad2008.cu

[digitalradio] Sub Channel DQPSK

[Rud Merriam]

Would the phase distortion that can corrupt a PSK signal occur the same on a
M-PSK signal?

If the phase distortion affects all the sub channels then doing differential
PSK among the sub channels would work where symbol to symbol DxPSK would not
work.

 
Rud Merriam K5RUD 
ARES AEC Montgomery County, TX
http://TheHamNetwork.net