[FoxHunt] IARU Transmitter question

[Charles E. Scharlau]

In a message dated 5/14/03 2:57:58 AM Eastern Daylight Time,
kuon@onlinemac.com writes:

>I'm making a change to PicCon's IARU mode, and have a question I need
>answered ASAP.
>
>Would it be OK to have the silence between MOEs be a fixed 1 second
>(approximate) delay, regardless of WPM speed of the MOEs?  Or does it
>have to be an official morse word space of 7 dit units?  I couldn't
>find anything in the rules.

  I don't see any problem with the fixed length delay.  The
  Montreal controllers seem to use fixed spacing between the
  start of each character group that is long enough to send
  MO5 - this gives an annoyingly long space when hunting MOE
  (and especially MO!)  If you gauged the gap for somewhere
  around 8 to 10 wpm it may sound a bit funny at slower speeds,
  but should be fine in the normal range.

    - Dale WB6BYU




It wasn't until I hunted using an AM transmitter to track an FM fox (slope
detection) that I realized the problem with how the original Montreal
controllers sent code characters. They do as Dale describes. They send their
"MOx" identifier at 6-second intervals regardless of code speed.

With an AM receiver I could only track the fox when a tone was being sent.
Which meant that only for a small fraction of the 1-minute cycle was I able
to actually track the fox. When using a receiver capable of detecting the FM
carrier I was able to track the fox for the full minute.

That experience prompted me to carefully read the Region 1 ARDF rules, and
they are pretty clear. The fox transmitters are supposed to transmit
International Morse code characters for the full minute. Unless the rules
had specified otherwise, standard spacing should be assumed. I also tested
some Russian transmitters. They do use standard code spacing, and in order
to transmit for the full minute they will keep sending until the last second
of their allotted 1-minute, even if it means that they get cut off in the
middle of sending a character.

Using a 1-second separation between "MOx" transmissions would probably work
just fine. But if you use the controller for an international competition I
think you might get some complaints. The complaints would have some merit
(especially for those using AM receivers) if the 1-second interval isn't
equal to or shorter than the 7-element standard spacing.

When Region 2 writes its ARDF rules we should consider whether to require
that FM transmitters turn off their carriers between "MOx" transmissions.
This would level the playing field between those using AM receivers and
those with receivers equipped with S-meters.

In the meantime I've reprogrammed my Montreal controllers to send the
callsign identifier first, and then they transmit standard code characters
and spacing until the end of their transmission.

- Charles NZ0I