ASA Electronics MS250 Symptom, Cause, Possible Solution, Am/Fm Reception, Yadaptors, Mast Length

TROUBLESHOOTING CHART

APPLICATION NOTES

AM/FM RADIOS

Symptom	Cause	Possible Solution
No Power	No 12VDC	Check circuit fuse at source
		Check in-line fuse on power
		lead
		Power lead disconnected
		Ground connection
		disconnected
Power indicated;	No 12VDC to memory	Circuit fuse at source
	lead(electronically	In-line memory lead fuse
no audio output
	tuned units only)
or very distorted
sound	Speaker Output	Check continuity of speaker
	shorted	leads to ground
	Speaker out cross	Check for proper speaker wiring
	channeled	Note: Radios have a sticker on
		them explaining wiring color
		code.
Only one channel	Radio Balance	Check radio function
(right or left side)
	Speaker Disconnected	Check speaker connection at
		radio and/or speaker
	Speaker lead shorted	Check speaker wiring continuity
	or grounded	to ground w/tester or meter
Popping in one or	Speaker wiring shorted	Leads from speaker cone to
both channels	or positive lead	terminal touching metal basket
	grounded	or speaker
	Speaker terminals
	grounded or shorted
No AM Reception	Antenna disconnected	Connect Antenna
	Antenna mast grounded	Check antenna or substitute with
	or shorted	antenna known to be good
	Antenna center lead	Check antenna or substitute with
	broken	antenna known to be good
	NOTE:Antenna leads can be tested with continuity or
	multi-tester. Some may have electronic component
	(capacitor) built in which not allow it to be tested.

AM/FM RECEPTION

Some boats have more than one AM/FM radio.The best way to insure good reception is to supply a separate antenna for each radio. Other options available to supply adequate AM/FM reception to these radios are listed below, along with some general information in regards to radio reception.

"Y"ADAPTORS

The "Y" adaptors used to connect one antenna to two radios will compromise both AM and FM reception.

AMPLIFIED AM/FM ANTENNA

A popular second antenna that can be used is our AB-100 amplified AM/FM antenna . It is small and has a retractable mast that can be mounted vertically or horizontally. This antenna provides good FM reception , but the AM reception will be compromised to some degree because of the length of the mast.

MAST LENGTH

AM/FM antennas compromise AM reception by design . The optimum mast length for FM is approximately 30 inches which is the standard for most automotive antennas. The optimum mast length for AM reception is over 100 inches which is not practical for mobile applications.

Special circuitry in electronic tuned radios or AM trimmers in mechanically tuned radios, make up for some of this difference in optimum mast length for AM reception.

ANTENNA CABLE

Increasing the antenna lead cable ( adding extensions ) will reduce sensitivity of AM with electronic tuned radios.

GROUND PLANES

Ground planes are also important when considering antenna performance. Most automotive antennas are designed to be mounted on the metal body of the vehicle.

The metal body reflects the signal interference generated by the vehicle's electrical system while it also provides the ground for the antenna lead shield. All this is necessary in order to maintain a good signal, especially AM.

FM RECEPTION

FM reception can be received with a very limited antenna and strong local FM stations can be received without an antenna , depending on the circumstances.

CONCLUSION:

AM/FM reception is subject to the choice of an antenna and it's application. There can also be a variety of methods used to supply signal to both primary and secondary radios , but AM performance is the ultimate "test"

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