[RTTY] Bandmap ??

[Richard Ferch]

Hi Robert,

I'm not sure which software you are using with the bandmap feature, so I
can't tell you for sure why you can't QSY to the calls with a red surround,
but it sure sounds as if the software is flagging a station you've already
worked on that band and preventing you from calling the dupe.

As for spots being on the wrong frequency, reporting frequencies in RTTY can
be tricky. The standard convention is to report the frequency of the mark
tone, but not everyone knows this or agrees with it, and quite a few people
don't know how, which results in inconsistent spotting of frequencies. I'll
try to describe some of the reasons for this inconsistency.

Some radios have a true FSK mode in which the dial frequency corresponds to
the mark tone. If you are using one of these, spotting the correct frequency
is easy. However, not everyone has one of these radios, and not everyone who
has one uses FSK. Some radios have what they call an FSK mode which is
actually just LSB with narrow filters, and quite a few radios don't have any
FSK mode at all, and must use AFSK; in these cases, the radio's indicated
dial frequency is not the mark frequency, and spotting becomes trickier.

If you are using AFSK with the radio in LSB or USB, then your radio will
display the suppressed carrier frequency. With the MMTTY software, if your
radio is interfaced, you can select an option which will automatically
combine the radio's indicated frequency with the audio mark frequency to
derive the true mark frequency. This is described in the Help file under
Radio Control. If your radio isn't interfaced, you have to do the
subtraction (LSB) or addition (USB) yourself. A lot of people don't know
this or bother with it, and just spot the radio's indicated dial frequency.

Given the above, you can see that the same station might be spotted at
14085.000 (mark frequency), 14082.875 (USB with 2125 Hz mark frequency),
14087.125 (LSB with 2125 Hz mark frequency), frequencies 170 Hz lower than
these (reporting the space frequency instead of the mark frequency by
mistake; since mark is the higher radio frequency but the lower audio
frequency using LSB, it's easy to get confused), or some other frequency
(for example, not everyone uses the same audio tones; tones in the 1400 to
1600 Hz range are quite common). Just to add to the confusion, the MixW
software calculates the frequency from the radio and audio frequencies
correctly, but it uses the convention of reporting the centre frequency, so
frequencies spotted by MixW users are often 85 Hz low (14084.915 in our
example) relative to the mark frequency standard. This difference is pretty
small, though, not much bigger than a lot of folks' dial calibration errors.

Given the above, the best you can do is: 1) make sure you report your own
spot frequencies correctly according to the standard convention; and 2)
recognizing that not everyone else is as knowledgeable as you, be prepared
every so often to have to look 1 or 2 kHz down (for spots from people
spotting the LSB dial frequency), and if that still fails, 1 or 2 kHz up (in
case the spotter was using the USB dial frequency).

That's all just part of the charm of RTTY. It's also confusing enough that
there is a good chance I have got part of it wrong, in which case I'm sure
we'll hear about it!

73,
Rich VE3IAY