Alternator Filter
I have a Ford F-150 pickup, and have been plagued by alternator whine on my receive and transmit signals. I searched all over the place for a decent home brew filter, and finally ran across Jim's, KB1MVX, article at http://www.sanantoniohams.org/Tips/whine.htm I basically used his advice but opted to use twenty feet of 10 gauge wire instead of twelve gauge wire. I figured this would cut down on voltage drop. The first filter worked pretty well. I was able to cut the whine down from about S4-5 to about S-1, which is about what Jim predicted. I ended up making a second filter and hooking it up in series with the first one. This entirely eliminated the whine. The filter wasn't cheap but probably the most effective (dB attenuation per dollar).
| 1/2" Quick Links $5 ea | $10.00 |
| 40 feet 10 gauge primary wire ($0.60 per foot) | $24.00 |
| Anderson Powerpoles | $1.50 |
| Electrical tape | $1.00 |
| Nylon cable ties | $0.25 |
| Butt connectors | $0.25 |
| 4700 uf caps Radio Shack | $11.00 |
| TOTAL COST | $48.00 |
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| Here one of the filters is wired up. | This is the back side. Note that with the 10 gauge wire no space was left inside the 1/2 inch quick link. |
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| This is the first filter ready to try with Powerpoles at either end. | Here you can see the nylon cable ties used to keep everything in position. |
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To the left is the first unit taped up and labeled. |
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| Here I have connected the two filters together with two butt connectors. This filter configuration eliminated all the whine. | |
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