[OZAPRS] RE:Oz 30m.

Noel Rowe noel-r at clear.net.nz
Thu Apr 1 09:52:04 EST 2004

Ron asks a fair question:
>Question to Noel.  You previously stated that your have a MFJ TNC, which
>model?  And what radio too please?
I have an MFJ 1274B TNC that has had an updated eprom fitted to allow it
to be operated in KISS mode.  The origonal one did not allow that, and as
I operate multiple ports via the AGW packet engine, I needed KISS mode to
be compatable.  The 1274 is the same as a 1270, but with the extra feature
of a row of LEDs as a tuning indicator. It is dual 300 and 1200 baud, but
manually switched to one or the other.  The owners manual states that the
tones are 1600 and 1800 for 300 baud operation.  
The radio is a Kenwood TS 430S that I have owned from new.  Like most
rigs, it has a minor calibration error, a few Hz, that is not an issue -
if it was I have more than enough service gear here to correct it.   I
have no trouble with this radio feeding the above TNC and decoding VK and
ZL 40m traffic, without changing the dial setting.  When on 30m, I have
decoded ZL stations.  I have never decoded a VK 30m station with this
radio/TNC combination.
In my usual setup, all my HF and VHF ports are hardware ones.  In order to
chase and then decode the 30m signals I could hear with my ears, but not
decode, I fed the audio from the 430S over to a spare PC running sound
card ports under the AGW packet engine.    I did this to view the signals
across the frequency spectrum by using the tuning aid provided within the
AGW software.   The mystery signals were "off the dial" as far as the MFJ
tuning indicator was concerned.  I did not retune the 430S, as I was
decoding ZL generated signals via the TNC which was also still
operational.  The PC used was networked to the "radio" PC that runs the
node here, and anything I decoded via the spare PC would be seen as
another port on the node. 
Because the AGW packet engine soundcard ports use 2100 and 2300 as its
tones, and my radio was left set to USB and 10.147.600 to suit the MFJ TNC
and its 1600/1800 tones  (see Mike VK2BMM's well thought out posting
detailing all the permutations) nobody was more surprised than I when the
tones I had been hearing but not decoding appeared on the AGW tuning aid
as being right on the marks.  Left this way, once the propagation
improved a little, I decoded VK3WRM.  Overnight, in the few days I have
had that PC  running 24 hrs, I have had up to 34 correctly decoded
transmissions from VK3WRM and VK3MY-3.  A lot more of the latter stations
transmissions would get through if the three things being transmitted had
their timing randomised rather than often being sent all at the same time
as one long transmission.   
My case for questioning whether the VK stations are in fact on the
frequency that I had reason from past debate to expect to find them on, is
based on the fact that the radio is set for 1600/1800 tones but I am
decoding using 2100/2300 tones.  Therefore I concluded that the traffic I
was decoding was in fact transmitted 500 Hz too high - based on the
difference between the two tone groups.  
Noel, ZL3GR

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