FlDigi Freq Reads Backwards

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Using a 6500 with the 1.5 release in RTTY mode.  Seems to be working fine, snagged E51MQT this morning on 40 meters RTTY. I am damned happy! 

A very minor glitch, in the Fldigi waterfall it is set to not display audio frequency but the rig frequency.  I was using the audio freq previously but with the new RTTY mode have switched to using the slice frequency.  The frequency in the exact center of the panfall is correct (in sync with the slice) but if I click on the Flex slice at 14.082Mc, by way of example the Fldigi will jump to the opposite side of the center frequency and be off, 14,084Mc if tuned to 14.080Mc.

The frequency is dead on in the center  at the "sweet spot"  (2210cy) but the labeled frequencies are mirrored at the sweetspot. RTTY is using LSB and the updates to the XML file for the 1.5 RTTY addition are in place.  I do not have to hit RV and RTTY shows as a mode for the Flex. It's as if the XML file is missing one more item.

Made a few contacts in the CQWW-RTTY.  There were some stations really piled up close to one another but no problems to copy. 

I realise this is minor but would like the app to read correct.  Any input much appreciated!


_..--
k3Tim
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k3Tim

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Posted 3 years ago

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Tim - W4TME, Customer Experience Manager

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I can't tell where you are clicking to tune.  In the Fldigi waterfall display?

If I click on the SSDR display, the frequency is dead on inside the filter.
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k3Tim

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Sorry for causing confusion.  If I click in SDR windows the frequencies don't match.  If you hit QSY in fldigi then the FlDigi panfall is centered and the frequencies are dead on, but the scale on the Fldgi is running backwards.  I'll post up a pic and label what is happening.  Sorry it is confusing,

k3Tim
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Tim - W4TME, Customer Experience Manager

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Yes, the frequencies do not match.  Fldigi is designed for legacy radios with an audio frequency (AF) offset from the receiver "dial frequency" (slice frequency).  So Fldigi takes the dial frequency and compensates for the AF offset to determine the actual signal frequency. The RTTY mode in SmartSDR is not offset from the slice frequency, therefore Fldigi incorrectly calculates the signal frequency due to the AF offset.

I suspect if enough FLEX-6000 owners asked for an option where the Fldigi dial frequency (slice frequency) is used rather than compensating for the AF offset, the developers may consider adding a check box option for it.
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k3Tim

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The offset for the "AF Tone" I am not concerned about.  The Freq Display on fldigi runs left to right or right to left depending on if radio is in USB / LSB mode. 
I shall attempt to set the sweetspot so the frequencies shown by the slice and the fldigi are 1.0 Kc apart (instead of the 2210).  Thanks for looking at this as it's not the SDR but the fldigi programme.

Best Regards,

Tim --  k3Tim/6
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Tim - W4TME, Customer Experience Manager

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Tim - that frequency display to the right of the slice frequency *IS* the AF frequency or tome frequency of the generated signal.  When using RTTY mode in SSDR, setting the Fldigi RTTY sweetspot to anything other than the center frequency determined by the Mark and shift setting will put your signal outside of the SSDR predefined filter configuration. 

If this issue is troublesome, use DIGL mode in SSDR rather than RTTY and use the radio like a legacy radio.
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k3Tim

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Hi Tim,
The AFSK offset is of no concern so I'm fine with that. Will set the FlDigi scale back to the audio frequency instead of the RF freq and it won't be confusing.  This is really an anomaly in the way Fldigi is handling LSB Vs. USB.  Anyway, thanks for you expert opinion.

Feel free to skip over the following paragraph...
I don't want to open a can of worms (now where did I put the can opener) but why was RTTY implemented in LSB not USB?  I assume it is so the M/S are correct and not reversed. 


Thanks!
k3Tim/6
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Alex - DH2ID, Elmer

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Tim, there is a good article and discussion on eham.net about RTTY tones

http://www.eham.net/articles/27625

... Years ago the standard was set to use the frequency of the Mark tone. Also about this time the use of LSB mode for AFSK generated Mark and Space tones was also set as a standard on all amateur bands so everyone could copy the tones generated with the Mark frequency as the low tone and Space as the high tone. This was done to keep things simple. This was also before digital frequency displays and a number of transceivers with the analog display would have three marks under the dial. This was done to show the offset used between the different modes....

I have set all my digital programs (fldigi, HRD, MultiPSK, EasyPAL etc.
at USB. For RTTY I have to set HRD DM780 to  "Reverse" for SmartSDR
RTTY mode, to "Normal" for PowerSDR DIGU mode. Sometimes I get a bit
confused and I have to use my trusty IC-756PRO as a control RX in RTTY.

Some day in the future there will be an agreement to set everything digital
anywhere to USB, hopefully ;-)

Regards,
Alex DH2ID
(Edited)