LF: Re: Re: dcf39/dk8kw

[DL4YHF@aol.com]

Hello Uwe and group,

About the "mysterious"(?)  carrier observed on DCF/DBF (I think DBF is their spare transmitter):
As Uwe wrote:

>sri, Markus, but the screenshot does`nt convince me.
>sri, Wolfgang, I do not belief in "Kohärenzprobleme". 


In a direct mail to Uwe I called it "non-coherent signal",  but it meant exactly the same as Markus (DF6NM) explained here on the reflector a few hours later. I don't think there is any mysterious very-narrow-bandwidth coding.

DCF39 is intended to be received by simple receivers; and the transmitter simply does not care for a coherent carrier just because a few radio amateurs would like to use it as a high-precision reference (hi).


The reason for the incoherent carrier signal maybe this (with my basic knowledge ):
Switching from the "space" frequency to the "mark" frequency in the TX is done when the carrier signal Y(t) crosses zero. After an integer number of full sine wave periods (when Y(t) is zero again), the frequency is switched back again. This will not necessarily be the old phase of the "space" frequency before a data bit. So, as an effect, there is no coherent phase - as explained before. 

You could verify this with an audio phase meter. I did this some time ago and could see the phase meter jump around after every pulse train, but could not find a rule. Maybe the amount of phase shift is simply a result of the count of "ones" in the databits.


> I will see my friends at the Radio-Monitoring-Station Itzehoe
> (RegTP-Aussenstelle) to solve the problem (I make it my problem)
> by analysing the frequenzy using their equipment (I have been
> member of the staff).

Please let me know the results.

Good luck,
  Wolf DL4YHF

(now off to look for Dave G(M)3YXM in simple CW without coherence problems. No kite-friendly WX here at the moment,  nothing but blue sky and sun)