Garmin radio irritations

[Javelin]

I fitted a Garmin 300 radio recently.
Ran the extension cable through to the cockpit speaker and added a GHS 10i command mic.

I had an intermittent fault.
Sometimes the radio would turn on below via the command mic but the command mic had nothing on the screen.
Other times it was fine.
I twiddled with the connector and it seemed to help for a little while.
This went on for a few weeks until I decided to start again,
headlining down, re ran the cable, re fitted the connector.
It all worked for a day and then it started again.

Moored up at Harwich another boat was using the same mic so I asked to try it on his and suddenly he had the same issue.
Sent the mic off to Garmin and 14 days later they sent a new one back under warranty.
Shame I can't bill them for all the hassle.

The other REALLY annoying trait is the GPS update alarm.
For whatever reason if the radio doesn't receive a gps update for 10 minutes it sets of an alarm which is duly cancelled by hitting the ignore button.
I've never noticed a delay on the gps positioning so why the radio seems think there is one occasionally is beyond me.
Has anyone else had this issue?

 

[Bru]

Sounds as though the replacement mic cured the first problem

At the risk of staying the blindingly obvious, it sounds as though the VHF isn't getting a reliable position fix from the GPS

The alarm is due to the need for an up to date fix for DSC messages, particularly digital Mayday calls initiated by pressing the panic button

What type of GPS and how is it connected to the radio (NMEA 0183, 2000?)

 

[Javelin]

Data in NMEA0183 from Simrad GS25 via Navman 8120 and connected using the Garmin supplied loom extension.
The Navman is getting on a bit, it came off a local fishing boat but is still in good nick and everything seems to work fine.

Interestingly (or not) the gps data is also fed to to a raymarine fishfinder which displays position etc and also has an alarm if it does not recieve an update and I've never heard this alarm activated.

 

[Bru]

Hmm, my immediate thought is that the Navman NMEA output is probably the original RS232 based hardware and the Garmin the later RS422. Somebody posted a neat little circuit for a buffer to sort such problems out just recently

 

[cpedw]

I used to have a similar problem but with different equipment. The VHF is an XM DSC set and it used to use a Garmin 128 GPS. It would occasionally complain that that it had no GPS input though the GPS seemed to be OK. After replacing the GPS with a Garmin 152, 2 years later and the problem has not recurred.

Derek