[1000mp] Working RTTY

[Kok Chen]

On Sep 25, 2004, at 8:59 AM, Bob Main wrote:

> As far as if it is FSK or AFSK, to be honest I have no clue.  I know 
> that I use Hamscope and I have PKT pressed on the Mark V and it is in 
> USB because I made the change in the menu.  This stuff is all new to 
> me.

If you are using the Packet mode, then you are doing AFSK.

With FSK, you will be sending a keying signal and the rig will generate 
the mark or space signals for you. With AFSK, your modem generates an 
RTTY signal, but at the audio frequencies (in fact precisely like what 
you hear out of your speakers when you are tuned in to an RTTY signal). 
  This Audio FSK signal is then passed to the SSB modulator of the rig, 
where it is "shifted" up to the RF spectrum.

With AFSK, you need to take the usual precautions, for example making 
sure that you are driving a signal that does not turn on the ALC 
indicator.  FSK is a little bit more of a no-brainer to operate.

> Not that crowded?  Then it is obiviously my inexperience that has 
> kicked in because it is all guessing right now.  What I am finding, 
> and maybe you can help here is I have the AFC on the program turned on 
> because it seems it is easier with it to automatically adjust the 
> Mark/Space spacing than it is for me to guess.

If you have narrow (250 or 500 Hz) filters, you will most of the time 
hear only a single signal.

You can tune through that single signal and when it centers, you will 
be printing.  After a while, you can pretty much center an RTTY signal 
aurally and only using any display aid to fine tune.  With weak 
signals, the closer you can get to being perfectly tuned, the "cleaner" 
the print will be.

I find that the RTTY Roundup in January produces the most boisterous 
crowding.  Lots and lots of very loud signals.  But something like CQWW 
produces a more challenging environment, where you have to sift for 
very weak mults from among the loud QRM.

> What happens is a station calls CQ Test and then stops, I prefer to 
> listen a bit before I do anything being Novice and all.  During the 
> time that that station is paused the AFC shifts over to a close 
> station and tries to tune in on that one.

Yes.  For your type of operation, what is needed is a momentary "tune" 
push button for the AFC to achieve an initial lock and then stay fixed 
at that frequency, instead of trying to track a signal when it is 
engaged.  Very few rigs drift enough to need long term AFC.

Once you start using narrow band filters, you won't need that silly AFC 
button anymore.  Really.

73
Chen, W7AY