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Combined VHF/GMRS + automatic “Rewind” of last transmission

This new handheld MR HH425LI VHF from Cobra looks very interesting especially if you live in North America or Canada and need to use GMRS as well as a marine VHF. GMRS and FRS are for personal and family use in the USA and Canada. FRS is normally a 0.5W transmission by the way, and requires no FCC license – but this unit will require a license because it is capable of transmitting up to 5W.

Cobra rew1But for all of us poor saps that live in the UK, I like the “”Rewind” feature which I haven’t seen on any other handheld. This means that the last 20 secs of any inbound transmission is automatically recorded – what a great idea for all those times when the CD/MP3 player is wacking our those golden rock oldies from the 70’s, or when the engine noise is drowning out the fixed VHF down below and you forgot where you left the handheld anyway…

The unit can also record your own transmission out if you want it to and this appears to be held in a separate memory to the inbound recording – well done Cobra for a simple and effective enhancement.

pdfYou can download the manual for the handheld MR HH425LI unit here if you want to read up on the Rewind feature or for European sailors to look up the GMRS features – why don’t we have this over here ! To see a short video of the Rewind feature in use have a look at the Marathon Leisure Site

The only problem is that it does not do DSC – this is an oversight for the European market.

If you are in Europe and you want the Rewind feature and you want DSC then Cobra only offer the fixed mounted radios such as the MR F80B.

Ok, who will produce the first handheld with VHF/GMRS/DSC and Rewind ?


Connecting Phillips Navigator MK8 to a MT500 DSC/VHF

Philips MK8After a recent correspondence via this blog, I thought it would be useful to publish the interface information for this connection.

The Philips MK8 has two cables both with shields BUT the shields will only be connected at one end – this is the clue. So at the MK8 end there is a D-SUB 9 pin connector – open it up and have a look at the wiring….it is wired as follows:



Pin 3 – Red – NMEA OUT (to a listener)
Pin 8 – Black – NMEA OUT (to a listener)
Shield – connected to MK8 shield
(DO NOT connect the shield at your Listener end)

Pin 2 – Red – NMEA IN (from a Talker)
Pin 7 – Black – NMEA IN (from a Talker)
Shield – NOT connected to MK8 shield
(DO connect the shield at your Talker end)


Connect to Phillips Mk8
1 Brown – INPUT DC + <<<<———- signal from Pin3 RED wire on MK8
2 Red – INPUT DC – <<<<———- signal from Pin8 BLACK wire on MK8

Connect to PC – Serial cable
3 Orange NMEA OUTPUT +
4 Shield NMEA OUTPUT –

Connect to Flash programmer
5 Green – Clock
6 Blue – Reset
7 Grey – PDI
8 Purple – PDO

Now to the NMEA Protocol

If you have done any research you will have realised by now that the NMEA protocol is really a very poorly implemented “standard” . What you have discovered about the wiring carries on into the programming of the chips that send the data. This standard is the NMEA 0183 protocol – now replaced by NMEA 2000 – which is also badly implemented. Just in case you are asking why – it is because manufacturers have used this confusion to protect market share and make their equipment incompatible on purpose.

NMEA 0183 version 2.0 sentences for GPS all start with $GP and then a 3 letter acronym.

$GP*** Sentence Titles
APA: Autopilot Sentence “A”
APB: Autopilot Sentence “B”
BOD: Bearing, Origin to Destination
BWC: Bearing and Distance to Waypoint, Great Circle
GGA: GPS Fix Data GLL: Geographic Position, Lat/Long
GSA: GPS DOP and Active Satellites
GSV: GPS Satellites in view RMA: Recommend minimum Specific Loran-C Data
RMB: Recommend Minimum Navigation Information
RMC: Recommend Minimum Specific GPS/TRANSIT Data
ROO: Waypoints in Active Route (not in standard)
RTE: Waypoints in Active Route or GOTO
VTG: Track Made Good and Ground Speed
WCV: Waypoint Closure Velocity
WPL: Waypoint Location
XTE: Cross-Track Error, Measured
ZTG: UTC & Time to Destination Waypoint

So you can see that when the MT-500 DSC manual says $GPRMC / GGA they mean that the two sentences above must be being sent by the Phillips MK8.

The Phillips MK8 does comply with NMEA 0183 version 2.0 (January 1992 standard)

It will transmit RMC (Time, date, position, course, and speed data) every 2 seconds.

BUT it will also transmit GGA – Global Positioning System Fix data (Time, position, fix) if you have the MK8 with differential software. This was issued as a software upgrade after the MK8 started shipping.