SJ23 Tech Tip E17, (Updated 2017-06-19) Bob Schimmel

Index

Install a Digital Media Receiver (Stereo).
INDEX - Features, Power, Antenna, Speakers.

While it may seem odd that my choice of a media receiver is an AM/FM/Cassette radio equipped with a manual shaft tuner, my rational is that it draws mere milliamps when switched on and does not draw power when switched off.  It also stays on station with the power switched off.  No digital media receiver is capable of all this.  The power drain to support receiver memory is the primary reason why a car battery is dead after a two week vacation.  All loads are switched off when I leave Panache so all the solar charge goes into the battery.  I can play endless music from my iPhone by plugging in a purpose made cassette equipped with an audio cord that plugs into the headset jack of my iPhone.  I thank my son for finding this matching piece of archaic electronics in a Goodwill store.  All well and good but it was also the technology of the day.

FEATURES - But that was then!  Unfortunately, my vintage receiver died during the summer of 2016 and I can't find an equivalent to replace it.  I actually found a couple of nice retro receivers but they are ridiculously expensive and still aren't 100% compatible to an original analogue unit.  So after much research for a replacement unit I've conceded that the additional features of a digital media receiver "might be useful" after all and my dual solar panels can handle the memory power drain and higher operating current.  I decided on an aftermarket marine Kenwood KMM-BT315U digital media receiver(Its called a receiver today because it has many inputs from which to receive a signal; AM/FM tuner, USB jack, Aux jack, Blue Tooth, etc.  That's my theory and I'm sticking to it!).

  • Single DIN mounting sleeve for small installation foot print and easy access to service the receiver.  There is a front panel bezel for a nice cosmetic finish to hide the sleeve.  {Dimensions of a DIN slot are: 2-1/8 (50mm) high by 7-1/8 (180mm) wide}.  The receiver slides into and locks in the mounting sleeve that is very secure for marine operation.  It comes with two extraction keys to remove the receiver from the mounting sleeve.  This is typical of most DIN after market receivers.
  • Removable receiver and detachable front panel.  (Perfect for winter storage to protect the LCD from condensation damage).
  • Conformal Coating for Marine use.  (Protects the components from condensation related corrosion).
  • Display illumination is programmable through 24 colours to match other instrument lights.  (Can also assign a different colour to a switch to draw your eye to that critical control on the front panel).
  • Blue Tooth technology for hands-free cellular operation using the speakers and wired external mic.  (Max 2 cell phones can be paired).
  • Blue Tooth for audio streaming from smart phone or tablet.
  • AM/FM radio tuner with 18FM/6AM presets, seek & scan. (AM has a longer range to detect lightning).
    Auto program feature to populate presets.
  • AUX jack on front panel. (Head set or to connect this output to the input jack of another device).
  • USB jack on the front panel with 1.5A charging capability. (Compatible with select Apple or Android devices for charging or playback of MP3, WMA, WAV, FLAC, and AAC files.  Music files can also be played from the USB drive).
  • 4 Speakers, 22W per speaker.  (You'll go deaf at this volume!).
  • SiriusXM satellite ready (requires service contract), plus support for Pandora Internet Radio (Android) and iHeartRadio (iPhone). (Requires a downloadable application installed on the smart phone).
  • Wireless remote control included. (Why you need this in a vehicle is beyond me).

LIGHTNING DETECTION - If you are considering a digital receiver, make sure it includes an AM/FM tuner that can be manually tuned.  The advantage of having AM, besides listening to news or sport reports, is that it can be tuned off station to become a fairly effective lightning detector, albeit without an alarm.  You just have to crank up the volume and listen to the lightning activity as it happens. 

CELL PHONE - An advantage of having Bluetooth for hands free cellular operation is that you are more likely to hear an incoming phone call over the system speakers (the music is automatically muted with ringing) plus the hands free operation eliminates the risk of dropping your cell phone when your hands are wet.  Real handy when the boat is heeled or in wet weather.  The music resumes when the call is terminated.
 

WIRING HARNESS - The easiest way to make the wiring harness is away from the boat.  Use same gauge stranded wire as manufacturer and make it about 2' longer than you think is required.  Splice the extension wires to the stub wire ends of connector D (shown below) by soldering and insulating with heat shrink.  Its probably a good idea to extend all the wires, even if you think it isn't needed now.  But insulate the unused ends to protect the receiver.  Fit the harness in place on the boat and cut it to length, leaving about 1' or more of slack at the back of the receiver.  This should be sufficient to handle the receiver when it is removed from the mounting bracket.  Remove the cable from the boat to install the spade lugs (crimped and soldered) on each lead and label each wire as per the schematic below.  There is nothing more frustrating than to trace unlabeled wires once a harness is installed.  Slip on some harness protection (spiral or split wrap) to protect the cable from abrasion.  Install a rubber grommet where the harness goes through a hole.  Now is the time to install the wiring harness in the boat and form the cable in place.  Connect the spade lugs to a terminal strip located close to the power panel for an organized installation and convenient trouble shooting later on.  All connections are polarity sensitive, so be very careful.  Confirm everything before making a connection.  It is doubtful anything will go wrong with your installation if you follow these steps.  The wiring diagram shown below is typical of many after market receivers.  Where the diagram refers to "car" substitute it with "power panel" as per your boat.


 

KENWOOD MEDIA RECEIVER WIRING HARNESS
TO BOAT DESIGNATION TERMINAL STRIP (TS3)
Bulkhead FL Front speaker (left) + (Wh)     1 - Cable I, Wh
Bulkhead FL Front speaker (left) - (Wh/Bk)     2 - Cable I, Gn
Bulkhead FR Front speaker (right) + (Gr)     3 - Cable I, Rd
Bulkhead FR Front speaker (right) - (Gr/Bk)     4 - Cable I, Bk
Companionway RL Rear speaker (left) + (Gn)     5 - Cable II, Wh
Companionway RL Rear speaker (left) - (Gn/Bk)     6 - Cable II, Gn
Companionway RR Rear speaker (right) + (Pr)     7 - Cable II, Rd
Companionway RR Rear speaker (right) - (Pr/Bk)     8 - Cable II , Bk
(not used) Antenna control + (Bl/Wh)     9 - Cable III, Wh
(not used) Steering control + (Bl/Yl)   10 - Cable III, Gn
BKR8 Switched power + (Rd)   11 - Cable III, Rd
(not used) Mute control + (Bn)   12 - Cable III, Bk
BKR14 Constant power + (Yl)    BKR14, Yl
Gnd Buss bar (BB3) Ground - (Bk)    BB3 - x

This Kenwood receiver draws 4 A with low volume and the memory draws 5 MA with the unit switched off.  I've researched 3 other manufacturers and they all draw about the same amount of current which means they use similar electronics.  You should determine if your charging system can keep ahead of this power drain.  The memory drain can deplete a battery with time if it is not charged by a solar panel or other source.  Keeping the receiver off when the battery is low will make the difference in starting your electric start outboard.  Always keep a starter cord handy.

If you want quality sound to listen to your favourite music/radio station then you need clean power and a good antenna.

  • POWER - A digital receiver requires two power feeds; switched (ignition) and continuous (battery).  Of the 3 units I've checked out, all maintained memory power after switching the ignition off.  Clean power can be had from the power distribution panel if it is equipped with a ferrite suppressor over the positive wire.  A ferrite blocks all spurious RF, noise spikes and ignition noise riding on the power line.
     
  • ANTENNA - If you don't have a marine grade broadcast antenna then a good antenna can be made from 75 Ohm coax (RG59) cable.  Strip about 30" of braid from the end and leave the remaining braid to shield the center conductor from radiated RF and/or ignition noise.  Insulate and seal the end of the braid and center conductor to prevent corrosion.  This antenna is designed for FM but works well for AM too, just like on a car. 
    - Just like the VHF antenna, height is everything.  You can be clever and slip the co-ax cable inside a hollow braid poly line and hoist it up as a flag halyard to keep it out of the way.  This is the same technique I used to install wiring inside the mast in Tech Tip E09.
    - An emergency VHF antenna can also operate satisfactorily for AM/FM if it is clamped on the stern rail.
    - Because an SJ23 mast is deck stepped, you can't just shove the co-ax cable through the deck and then to the mast.  The cable would be ripped apart as the mast is laid down.  A good technique is to install a marine bulkhead connector above the deck and screw a dust cap on the deck connector when the antenna cable is removed. 
     
  • SPEAKERS - One final point about stereo sound quality; all speakers must be phased correctly.  That is, the cones must move air in the same direction when the same polarity is applied.  If they are wired opposite, the speaker furthest from you sounds dead.  So connect the positive of the audio out to the positive of the speaker and the negative to the negative. You can use an Ohm meter to confirm the polarity of the speaker wiring, watching the speaker cone move as you momentarily touch the terminals. 
    - If your speaker magnets are not magnetically shielded it's a good idea to cover them with a ferrous shield.  The end of a metal food can is the perfect shape provided it magnet attracts it.  Use a diameter that is just a bit wider than the speaker magnet.  The closer the can is to the magnet, the more effective it is.  Shorten the side of the can so it covers the side of the magnet just short of the speaker frame.  You may have to cut a notch in the side to clear the speaker terminals.  Insulate the cut edge in case the can rotates.   Line up the notch with the terminals and place the can the over the magnet.  The magnetic force will hold it in place.  This can should contain the majority of the magnetic field and result in a truer reading on the ship compass.  You can test it with a handheld compass.  Install the speaker no closer than a 1' away.  The cans will not affect the sound quality.
    - My two additional speakers will be mounted under the companionway, facing towards the cabin in poor man's quadraphonic style for optimum sound quality in the small cabin. 

                               Front speakers on bulkheads                                                                 Rear speakers under companionway

    

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