Batboard

I have noticed I have a whine when recieving on my Spectra. What can cause this? Its mostly when my truck is idling. But my gauge is showing 14 volts. Sometimes 15. Bad ground or what?

There are several possibilities for a source of alternator whine in any vehicle with a standard alternator-regulator-battery electrical system. Assuming that your Spectra is wired directly across the battery as recommended, you can start by checking the age of the battery(internal resistance increases with age and grid corrosion). Capacity test the battery or have a reliable automotive service shop perform the test. When powering an accessory like a radio, the battery effectively acts like a huge filter capacitor because of its very low impedance if it's in good shape. Next, check the alternator for open diodes - alternators are three phase AC generators with a three phase diode full wave rectifier on the stator winding leads. If a diode opens up, the alternator will not deliver rated output current at rated speed. Your automotive service shop can check current output at the rated shaft speed, and if a diode or diodes are faulty they shold be able to spot it right away. Finally, if the battery and alternator are in good shape, some filtering on the ignition sense lead may be required to eliminate the problem. You didn't say whether the radio has had a whine problem since installation or whether it started recently. If the problem appeared recently, I'd bet on the battery.

"Alternator" whine is actually caused by the alternator regulator (which is internal to most vehicular alternators). The regulator varies the output current of the alternator to meet load, and it does this by varying current through the alternator's field wiring. Not uncommonly, the regulator functions as a high frequency switcher, and this is the cause of the whining noise.

The field must be grounded, or else the alternator would make no output. Some alternators use an external ground for power (versus relying upon case grounding), and if this ground becomes impaired it can increase regulator noise. However, the usual solution to regulator whine is to put a noise filtering cap between the output and ground. I believe that Newmar is the brand of one commonly used alternator noise filter.

ive just started hearing it since it started getting cold outside. May the the battery its couple years old. I think my alt is good as its holding 14+ volts when running.

the battery is not capable of creating alternator noise, it's something with the charging system, not what's getting charged.

As a guess (which all long distance diagnoses necessarily are), I'd say the regulator is failing (or possibly the alternator), and given the cold and some extra load, the regulator is running wide open in an attempt to stay up, and this is causing the whine.

Alternators are consumptive devices. In a car, they usually aren't asked to do too much. In certain marine installations, on the other hand, the alternator may be asked to do significant recharging of batteries, and there they work hard. By definition they get very hot, and they draw a lot of dirty air through the case. On our boat, we swap alternators every 4-5 years and have the old one rebuilt.

dbfd588 wrote: started hearing it since it started getting cold outside. .

Bad capacitors in the Spectra radio. The caps have leaked reducing the capacitance value, The capacitance values decrease even more when cold. Not enough capacitance to filter out noise on the A+ battery line.

bought it from a fellow Batboard member. He said the radio and head had new caps. But I wouldnt know if it didnt. Im not that technicaly inclined. I just took his word for it

Hello :
Not saying this is true in your case but i had a fellow friend complain about a radio with the whine in his combine.
We tried pretty much everything but couldnt quite get all of the whine out even with pos inline power filtering.
The following combine season the batterry gave him troubles and he replaced it.
The whine went away and was also gone when we removed the power in line filter.
So while i would agree that the battery cant produce the whine but if its not in very good shape it can make the alternator work hard enough to produce a whine.
At least in this paticular case it did.
Satelite

yea thats my theory. Im just gonna have to have them checked. Thanks everybody for the input