[RTTY] Spot frequency

[Joe Subich, W4TV]

 > So how exactly is this done?

If you must use AFSK - even though the FT-1000 and its siblings make
FSK so much easier - use the MENU SYSTEM to set things correctly (it's
all in the manuals).

Menu 6-4 "Packet Display Offset":  Set to the MARK tone (-2.125 for LSB)
Menu 6-5 "Packet tone frequency":  Set to the MARK tone (2125 default)
Note: if you use AFSK tones other than the traditional "High Tones"
(2125/2295) replace -2.125/2125 with your MARK tone frequency.

It is as SIMPLE as that to make the PKT mode in the FT-1000 family of
transceivers display correctly when using PKT mode for AFSK.

73,

    ... Joe, W4TV


On 6/13/2010 9:06 PM, Jerry Rappel wrote:
>
> That said, good rigs won't have this problem if you set them up
> correctly. The menu of the FT-1000MP for example, allows you to apply
> a dial offset to the AFSK ("PKT") mode.
>
>
> ---------------------------------------
>
>
>
> So how exactly is this done?
>
> Thanks,
>
>
>
> Jerry  WWØE
>
> ==============================
>
>
>
>> From: chen at mac.com Date: Sun, 13 Jun 2010 18:01:08 -0700 To:
>> rtty at contesting.com Subject: Re: [RTTY] Spot frequency
>>
>>
>> On Jun 13, 2010, at 5:18 PM, Gary AL9A wrote:
>>
>>> I seem to remember this was due to the 2125 Hz shift. Is this a
>>> difference between running FSK or AFSK?
>>
>>
>> By convention, RTTY signals are identified by the Mark frequency.
>>
>> Most radios when operated in FSK mode will display the mark carrier
>> as the VFO dial frequency. So, the problem is most likely *not* be
>> originating from you.
>>
>> But take the case of an AFSK op who just worked you (and presumably
>> zero beat with you)...
>>
>> If his VFO dial is showing the suppressed carrier frequency of an
>> LSB transmitter, and he using the 2125/2295 tone pair, then his
>> (and your) mark carrier will be 2.125 kHz below his dial frequency.
>> If he is spotting from his VFO dial, the spot will read 2.1 kHz
>> higher than your actual mark frequency.
>>
>> Now, what if he is using USB?
>>
>> In this case, assuming he is using the same 2125/2295 tone pair,
>> his mark carrier will be 2.295 kHz above his suppressed carrier.
>> (Notice that the mark, by convention is always the higher frequency
>> of the two RF carriers.) If he is reading off a VFO dial that
>> displays the SSB suppressed frequency, his packetcluster spot will
>> then be 2.3 kHz too low.
>>
>> That said, good rigs won't have this problem if you set them up
>> correctly. The menu of the FT-1000MP for example, allows you to
>> apply a dial offset to the AFSK ("PKT") mode.
>>
>> Even if the radio does not have that feature, software modems often
>> have a place where you tell it to how to label the waterfall
>> frequency. cocoaModem for example has a VFO offset box, plus a menu
>> to tell it if you are using USB/LSB and it will apply the
>> arithmetic gymnastics to display the number that has to be added to
>> or subtracted from the VFO dial to get the actual frequency of your
>> RTTY mark. cocoaModem will in fact reverse the waterfall (lower
>> tones appearing on the right side of the waterfall instead of
>> higher tones always on the right) when you transceive in LSB so
>> that the waterfall will show the higher RF carrier always to be on
>> the right of the waterfall.
>>
>> With all the tools at our fingertips, (including a calculator :-),
>> there should be no excuse for not spotting the mark frequency of an
>> RTTY signal properly.
>>
>> 73 Chen, W7AY
>>
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