[RTTY] FSK and ft-1000mp

[tgstewart@pepco.com]

Bravo, Chen!  It's been a while since I've messed with PSK, but what's the 
convention on that mode?  I usually avoid it like the plague, but I'm 
going to have to get up to speed on that for field day and an occasional 
DXpedition.

A couple of points I'll make about running "FSK" or "RTTY" mode on an MP. 
First off, I dont think it is true FSK.  My recollection is that the 1000 
series uses audio DSP to generate the FSK tones.  Perhaps a little cleaner 
than a sound card because there are no external cables, but a good sound 
card AFSK should be almost equivalent if you run good audio levels and 
dont overdrive the radio.  The big advantage to running AFSK on RTTY is 
that you can run TX autotune when you are S&P to exactly match the tones 
of the guy you are calling.  It's probably not so important these days 
since almost everyone is running RX autotune on a sound card, but it does 
help keep the adjacent channel interference down for the rest of us if you 
are exactly on his frequencies when you call.

Ty K3MM




Kok Chen <chen at mac.com> 
Sent by: rtty-bounces at contesting.com
03/10/2005 05:54 PM

To
rtty at contesting.com
cc
KO1H <KO1H at cox.net>
Subject
Re: [RTTY] FSK and ft-1000mp







On Mar 10, 2005, at 2:09 PM, KO1H wrote:

> Hi all, I have one question (after I worked out a bunch of problems 
> myself). I have gotten fsk working on my ft1000mp but I need to know 
> if I should have the Menu setting for Offset or Carrier. in the menu 
> settings?

You probably want "Offset" and not "Carrier," IMHO

"Carrier" would display the suppressed carrier frequency of the SSB 
receiver onto your VFO dial, which is pretty meaningless for figuring 
out where your RTTY signal is landing on unless you also know the tone 
pair that you are using.

If you have selected the 2125/2295 tone pair for example, selecting 
"Carrier" would display a frequency on the FT-1000MP dial that is 2.125 
kHz up from your mark carrier and 2.295 kHz up from your space carrier.

If you select "Offset," the FT-1000MP will display the frequency that 
your Mark tone lands on the RF spectrum, and is also the standard way 
RTTY "operating frequency" is defined as.

Having a direct readout of your mark on the RF spectrum makes it much 
easier to figure if you are "out of band" or transmitting on top of the 
DX beacons without having to mentally do some subtractions.

The majority of the folks also spot the mark frequency to the 
PacketCluster, so that is yet another reason to use "Offset."

>  I've worked everything else out I just need to know which of these 
> is the standard aka what will put my tones in the correct band pass 
> of the other stations receive when I have their tones printing at 
> mine.

Don't worry about the correct passband versus the tones; the FT-1000MP 
will perfectly center the IF passband to the tone pair that you have 
selected in the FSK menu, even if you'd choosen 250 Hz filters.  The 
choice of the tone pair to use is therefore an individual choice.  Some 
people prefer one of the lower tone pairs because it is kinder to the 
ears.

If you are using AFSK, then there is a reason to use the higher tone 
pair.  Using the 2125/2295 tone pair throws any harmonics up to 
frequencies beyond the SSB transmitter's bandpass filter and that helps 
provide some protection against overdriving.  Since you are using FSK 
on the FT-1000MP, where the digital synthesizer of the rig is doing the 
actual frequency shifting, this is not an issue.

73
Chen, W7AY




_______________________________________________
RTTY mailing list
RTTY at contesting.com
http://lists.contesting.com/mailman/listinfo/rtty


This Email message and any attachment may contain information that is
proprietary, legally privileged, confidential and/or subject to copyright
belonging to Pepco Holdings, Inc. or its affiliates ("PHI").  This Email is
intended solely for the use of the person(s) to which it is addressed.  If
you are not an intended recipient, or the employee or agent responsible for
delivery of this Email to the intended recipient(s), you are hereby notified
that any dissemination, distribution or copying of this Email is strictly
prohibited.  If you have received this message in error, please immediately
notify the sender and permanently delete this Email and any copies.  PHI
policies expressly prohibit employees from making defamatory or offensive
statements and infringing any copyright or any other legal right by Email
communication.  PHI will not accept any liability in respect of such
communications.