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SWR problems


SVO42

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SWR and fuel pump noise problems

I recently installed an old CB and Firestik antenna on my X, but am having problems with my SWR. It's slightly under 3:1 on ch 1, and over 3:1 on ch 40. I looked at the antenna but couldn't figure out how to adjust it. I took the cap off the tip and there was only fiberglass as far as I could see, and it was already mounted to a ball mount and I couldn't open that end up because I didn't have an allen wrench big enough. I'm going to borrow one and take a look, though. FYI all this equipment is about 25 years old (my dad's stuff).

I have the antenna mounted on the rear bumper on the right side (not the best place, I know, but this is my DD). Any advice would be appreciated! I can receive OK, as lonas as the X isn't running (fuel pump noise, but I've read all the FAQs on that).
 
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Sandy

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:cool:

The older FireStiks are adjusted by moving the coils, on the top of the antenna, a part a little at a time. Use the same method as cutting the metal shaft on the S/S whip type of antenna, small moves.

If you use all of the channels on your CB then setting the SWR for the top and bottom of the band is a good idea. If you are most of us and use one or two close together channels then try setting the SWR for the channel you use the most; let the SWR go where it wants on the other channels.

Fuel Pump noise is a big problem in the X, so you need to add the noise filter setup mentioned in the begining posts on this Forum.

If you continue to have noise problems you can follow through and get filters for all of the electrical components on the vheicle or you could move the antenna around to find a better, less noisey, location.

The best location will be the roof centered on the vheicle but a lot of people do not like it there.

Luck, take your time, get it right the first time.
 




SVO42

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So I need to peel back the black covering on the antenna and move the coils down? Should I keep the spacing the same, any special way to do it, etc.? I'd most likely just set the antenna to work best on channel 20.

I spoke with my local Ford dealer the alst two days about the TSB for the RFI. The part listed in the FAQ for 91-99 Explorers is no longer in production. :( Now I'm not quite sure what to do. Maybe I'll try making my own as in the FAQ thread in this forum. Some diagrams would be nice, though.
 




Sandy

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:cool:

Move them up or down where applicable.

The spacing isn't as important as the end results.

Always reinstall the cap before checking the SWR, it is suppose to make a difference.

Not sure where you can find a write up on adjusting the SWR but find it and read it.

There is a writeup at teh beinging of this forum about building an RF Filter, read it.

Ltr
 




SVO42

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OK, I made the RF filter as described at the top of the section. I used 5 RF chokes with 6-7 turns of insulated 16 gauge wire wrapped through each, making sure the wire went through the choke the same direction every time. I installed it inline with the power and ground wires for the fuel pump (which I had to test for with my multimeter since my Chilton's manual wiring diagram was wrong) about a foot or so away from the pump itself. I'm aware that the closer I get to the pump the better the noise reduction would be, but I didn't have time to drop the fuel tank today. FYI, power lead = pink/blue, ground = black for my '94.

IT MADE ABSOLUTELY NO DIFFERENCE!!!!!!!! :fire:

I have yet to adjust the antenna, could that have anything to do with it? What's going on here?
 




351wExplorer

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what is the best way to cut down on fuel pump noise???
mine is pretty bad
 




pickupman

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allright, start from the top.

1) your antenna is slightly too long. either push the coils together, or clip some wire off.

2) have you tested to find out if your noise is radiated or conducted? (see the sticky) putting a capacitor across the motor leads may actually be more effective than the chokes. The biggest concerns are the frequency of the noise, and the manner in shich it gets into your system.
 




Sandy

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SVO42 said:
IT MADE ABSOLUTELY NO DIFFERENCE!!!!!!!! :fire:
QUOTE]

Sorry that this mod didn't do it; not sure why not.

Either similar components weren't used or the noise isn't coming from the pump as much as you thought.

As pickupman stated start from scratch and see where the noise is coming from.

Remember this is only Radio Theory, it is a trial and error process that usually works but some vehicles have the particular noise problems.
Noise can come form a lot of places, not alway an electrical component, the noise can come from the hood or the doors not being grounded, the CB chassis not being grounded, there are so many things that can play into the mix.
Outside noise can be a problem too, electrical noise from the AC lines coming into the house, or even the lighting in your house or on the street.

Take your time trace out each component and shut them off, see if the noise goes away.

Luck,

Luck,
 
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