Rudy, don't' look, cover your eyes cuz this is about marine radios.

I have only come across one other boater between here and Key West who had a
DSC radio installed properly with an MMSI entered and who had the
inclination to experiment too.  That brief experience helped me a bit, but I
still had a number of unanswered questions about the DSC opertion of my two
radios when conducting "Individual" DSC calls.

Lacking anything better to do this COLD afternoon (temp 25F today at 0900),
I ambled down the pier to check on the anti-frost measures in place on the
boat and decided to entertain myself while there experimenting with my two
DSC radios.  One is a West Marine VHF 600 (Uniden), and the other is a
cheapie Standard Horizon Eclipse mounted side by side.  Their firmware
packages are quite different.

The Uniden has an option to disable automatic channel shift for Individual
Call - the SH Eclipse has no such option.  I don't believe canceling
auto-channel shift is possible for emergency DSC calls on the Uniden, where
it is supposed to shift to 16.  The Uniden also has an option to set
"Standby" under the DSC option menu which means that "Unattended" shows up
on the calling radio's screen when the DSC Individual Call is acknowledged
there while the Eclipse has a feature called "Individual Reply" which can be
set to "Auto" or "off."  The Uniden automatically cancels the "Standby"
feature when any key or the mic button is pressed.  The Eclipse's
"Individual Reply" setting requires operator access to the menu to change,
but neither the auto nor off setting prevents channel shift when an
individual call comes in.

The Uniden has the option to set Position Reply to auto or off - no such
feature exists on the Eclipse.

Both radios have the same MMSI.  I entered that MMSI with the name CALYPSO
into the Individual Call Directory of both radios in order to conduct some
tests.

The first thing I did was disable the automatic channel shift function on
the Uniden and then called from the Eclipse on channel 72 using its
Individual Directory to call up CALYPSO.  The Uniden shifted to channel 70
momentarily from channel 68 and started beeping loudly and indicated a DSC
call from CALYPSO before shifting back to channel 68, but because the Uniden
had the auto channel shift in "off," I could not determine which channel the
Eclipse was calling on.  Well, that wouldn't seem very useful in the real
world.  The Uniden's noisy beeping continued until a key was pressed on the
face of the radio.

Going the other way, I used the Uniden to call the Eclipse on channel 68
while the Eclipse's Individual Reply was set to "off."  The Eclipse shifted
from channel 72 briefly to 70 to accept the data and then shifted to channel
68, BUT the acknowledge signal was not sent to the Uniden until a button was
pushed on the Eclipse.  The audible alarm on the Eclipse indicating a DSC
call on the Eclipse is adjustable in the amount of time it bleeps from 2
minutes to 5 beeps.

I left both radios in full automatic for all functions, but may decide to
change the automatic channel shift setting on the Uniden to "off."  Since
both radios will normally be on when underway, both will indicate an
Individual Call when it arrives, but only the Eclipse will actually shift to
the calling station's frequency.  Thus, important ongoing communications on
the Uniden won't be interrupted by an Individual Call, except for the
possible brief shift to channel 70.  Emergency DSC calls trump all.

I invite your comments on my perceptions and findings.

Rich Gano
CALYPSO (GB-42 #295)
Southport, FL (near Panama City)

The Icom SC-101 class radios have a nice feature that I haven't
noticed on other makes - they allow you to turn off the Channel 70
scan, so they effectively become non-DSC radios (I think the Ch 70
scan is turned on, at least temporarily, if you do make a DSC call - I
should do some more tests....)

I have an Icom 504 (class D DSC) in the cabin (my primary helm location)
and an Icom 422 (SC-101) on the flybridge, each with a remote mic at the other
position. I have the channel 70 scan turned off on the 422, so that
only the 504 will respond/alarm on any DSC calls.  I think I have the
automatic channel shift turned off on the 504.

Sunday, January 10, 2010, 6:45:20 PM, Rich wrote:

RG> I left both radios in full automatic for all functions, but may decide to
RG> change the automatic channel shift setting on the Uniden to "off."  Since
RG> both radios will normally be on when underway, both will indicate an
RG> Individual Call when it arrives, but only the Eclipse will actually shift to
RG> the calling station's frequency.  Thus, important ongoing communications on
RG> the Uniden won't be interrupted by an Individual Call, except for the
RG> possible brief shift to channel 70.  Emergency DSC calls trump all.

RG> I invite your comments on my perceptions and findings.

RG> Rich Gano
RG> CALYPSO (GB-42 #295)
RG> Southport, FL (near Panama City)

--
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca