[TenTec] FSK

[DUANE BUDD]

I have recently started to use rtty and pactor.  I have had to set the rit
to -.13 to be able to connect.  Why?

Thanks
Tom Reilly
W3GAT

There will probably be submissions on this subject by those better qualified
to answer than I, but there has already been some misinformation submitted
and I thought I would take a stab at correcting it.

First, Tom, you did not state which Ten-Tec rig you are using. Speaking for
the Omni VI, the manual says the fsk shift is set to 170KHz, which is the
"correct" standard for RTTY. The "correct" new standard for PACTor is
200KHz. I have used 170 for years and until I got the IC-706MkII, never had
a way to use FSK with the 200-shift. I cannot tell any difference between
using one or the other.

One possible reason for your receive discrepancy may be the tones
themselves. The proper tones using the Omni VI are 2125 and 2295. For some
reason, the Kam+ defaults to a much lower setting. Note that this sets your
TNC to the same 170 shift that the Omni VI supports in FSK. If you do not
know how to set the tones in your TNC, let me know and I will send you a
personal Email, rather than take up reflector space.

With the following paragraph I run the risk of stirring up the old debate on
which is best, AFSK vs. FSK.

The main advantage using FSK has is that you cannot over-modulate using it
as you can with AFSK. When I started RTTY and added AMTor and PACTor as they
came along, that was the most frequent problem on the air, new users of the
digital modes overdriving their rigs on AFSK and splattering all over the
bands. With AFSK, the TNC does indeed generate the tones, but they still
need to be set to the proper values in the TNC.

You will enjoy the digital modes. Like the Ten-Tec bunch, the hams on the
digital modes are, by and large, the cream of the crop (OOPS! My opinion
just slipped out. Sorry about that.)

73

Budd, K4AAE


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