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@mac.com
> Date: Sun, 13 Jun 2010 18:01:08 -0700
> To: rtty@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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