Dick Kriss aa5vu-fOdFMYwuEsI@public.gmane.org [linuxham]
2014-08-11 16:43:22 UTC
The following is a copy of my posting to the Kenwood TS-590S reflector regarding and number of questions raised about RTTY and digital modes that may be of interest to new fldigi users. Yes, I know most of this is covered in the manual but from the comments it was obvious many have read but forgot some of the good stuff.
Again, TNX to Dave W1HKJ and the fldigi development team for a great digital application that keeps getting even better.
I changed the subject because a number of RTTY and digital questions have been raised and some had multiple topics in the same message. I will try to address some of the confusing topics.
Regarding AFSK vs. FSK many of the radios in use today were designed before the advent of sound card technology and the designers at that time assumed all RTTY would be FSK so they put an FSK mode button on the face of the rig and optimized the filters for FSK. In the old manuals you will see a few comments about AFSK associated with HF Packet. With the advent of the sound card technology, users put the older radios in USB and found they do not have access to the FSK RTTY filters so they stay with FSK. I know one user that receives FSK on VFO-A and transmits on VFO-B in AFSK. His reason for doing this is because his logging program is keyed to rig frequency display. Talk about the tail wagging the dog.
We do not have this issue with the Kenwood TS-590S. It has a full range filtera when you have the TS-590S in USB DATA mode. Note I said USB DATA mode and you will find the IF FILL button is your friend for digital modes in USB DATA.
In the old days the RTTY Mark was king and all RTTY QSOs were logged at the Mark frequency and this was adopted as the standard and it is still in practice today. Today we still log and spot RTTY QSOs based on the Mark frequency - even in AFSK.
In fldigi the Mark is the green track on the waterfall and red track is the space. Also, in fldigi there are two frequency displays. One for the rig Dial frequency the other is the Operating or QSO frequency. When you have fldigi in RTTY mode, the Mark (green line on the waterfall) is the QSO frequency and that is also the frequency that is logged. In other digital modes the QSO frequency is the centroid (center) of track on the waterfall display.
The difference between the rigs dial frequency and the QSO frequency is the determined by the user selected Sweet Spot in the fldigi (Misc/Sweet Spot) configuration panel. I use 1000 because it easy to mentally subtract by 1. For example, if i see a spot on the cluster that says there is a RTTY station I want to work at 14087.5, it easy for me to spin the VFO to 14086.5 (down one) and start looking in the waterfall. If I see the tracks on the station down a little I mouse select the tracks and fldigi starts printing to the screen. i then use the fldigi QSY button to bring the station to the sweet spot. The reason I want the station centered at the sweet spot is so my transmitted signal will sound right. With regard to the term sound right i am sure you have heard some weird sounding CW and RTTY signals on the bands. This is caused when an operator transmits outside the sweet spot. Using the fldigi QSY button centers the rig VFO to where you are receiving - and the transmitter follows. Failure to center causes your transmit to be off resulting in weird sounding signals.
I could go on but dont want to bore people with unwanted nitty-gritty details. The bottom line is the TS-590S is a great radio for sound card AFSK RTTY and digital modes because we can optimize the filters where we needed. Users with older rigs may have to use a 1500 sweet spot because they are stuck with fixed Rx filters.
Get to know how the TS-590S IF FIL works. It is one of the best features in the rig for digital modes.
73 Dick AA5VU
PS: Years ago I ran FSK for RTTY but now that I have learned the correct way to use AFSK, I no interest in going back to FSK.
Again, TNX to Dave W1HKJ and the fldigi development team for a great digital application that keeps getting even better.
Subject: Misc RTTY and Digital Questions
Date: August 11, 2014 at 9:14:54 AM CDT
*** quote marks cut for reading ease ***Date: August 11, 2014 at 9:14:54 AM CDT
I changed the subject because a number of RTTY and digital questions have been raised and some had multiple topics in the same message. I will try to address some of the confusing topics.
Regarding AFSK vs. FSK many of the radios in use today were designed before the advent of sound card technology and the designers at that time assumed all RTTY would be FSK so they put an FSK mode button on the face of the rig and optimized the filters for FSK. In the old manuals you will see a few comments about AFSK associated with HF Packet. With the advent of the sound card technology, users put the older radios in USB and found they do not have access to the FSK RTTY filters so they stay with FSK. I know one user that receives FSK on VFO-A and transmits on VFO-B in AFSK. His reason for doing this is because his logging program is keyed to rig frequency display. Talk about the tail wagging the dog.
We do not have this issue with the Kenwood TS-590S. It has a full range filtera when you have the TS-590S in USB DATA mode. Note I said USB DATA mode and you will find the IF FILL button is your friend for digital modes in USB DATA.
In the old days the RTTY Mark was king and all RTTY QSOs were logged at the Mark frequency and this was adopted as the standard and it is still in practice today. Today we still log and spot RTTY QSOs based on the Mark frequency - even in AFSK.
In fldigi the Mark is the green track on the waterfall and red track is the space. Also, in fldigi there are two frequency displays. One for the rig Dial frequency the other is the Operating or QSO frequency. When you have fldigi in RTTY mode, the Mark (green line on the waterfall) is the QSO frequency and that is also the frequency that is logged. In other digital modes the QSO frequency is the centroid (center) of track on the waterfall display.
The difference between the rigs dial frequency and the QSO frequency is the determined by the user selected Sweet Spot in the fldigi (Misc/Sweet Spot) configuration panel. I use 1000 because it easy to mentally subtract by 1. For example, if i see a spot on the cluster that says there is a RTTY station I want to work at 14087.5, it easy for me to spin the VFO to 14086.5 (down one) and start looking in the waterfall. If I see the tracks on the station down a little I mouse select the tracks and fldigi starts printing to the screen. i then use the fldigi QSY button to bring the station to the sweet spot. The reason I want the station centered at the sweet spot is so my transmitted signal will sound right. With regard to the term sound right i am sure you have heard some weird sounding CW and RTTY signals on the bands. This is caused when an operator transmits outside the sweet spot. Using the fldigi QSY button centers the rig VFO to where you are receiving - and the transmitter follows. Failure to center causes your transmit to be off resulting in weird sounding signals.
I could go on but dont want to bore people with unwanted nitty-gritty details. The bottom line is the TS-590S is a great radio for sound card AFSK RTTY and digital modes because we can optimize the filters where we needed. Users with older rigs may have to use a 1500 sweet spot because they are stuck with fixed Rx filters.
Get to know how the TS-590S IF FIL works. It is one of the best features in the rig for digital modes.
73 Dick AA5VU
PS: Years ago I ran FSK for RTTY but now that I have learned the correct way to use AFSK, I no interest in going back to FSK.