rf issue

[serrasalmus]

hi guys long time lurker nvr posted not really smart enough to add to anything you guys have to say....

i got a 2970n2 and a pred 10k on a breedlove puck and im getting some rf issue's..
i have bonded all doors with ground strap (1/2 braided tined from Georgia copper all ends soldered), the hood and the tailgate. i have upgraded the stock alt cable with 1/0 gauge along with the ground from bat to alt casing also 1/0. have bonded motor to frame i have pics if needed. the issue i get is its coming thru my stereo and also messing with my idle. now the idle on my vehicle is controlled by a idle air control valve basically it is a electric plunger that adjusts the airflow into the intake and controls the idle. it will make it go up and down about 200-300rpm in am in ssb about 100-150rpm according to my tach. i don't know what else to do to fix this issue as i cant unplug the iacv without major issue's (it controls the idle when i turn on the a/c and at 105+ most of the time a/c is a must, and it throws a ses light)
the radio is wired to the bat with 8gauge and grounded to the body, coax used is 18ft of lmr 240, swr is 1.3ish i don't have a good meter but the two i have (one being in the radio and a aries) say roughly the same.

on a good note talked to new mexico for the first time tonight...and cant wait till i get my tech to talk on 10m

thanks in advance for your help and have a good day/night...

 

[unit248]

Hm. Well, first, let me say I don't know much about cars. I think there are two possible scenarios where. The idle air control valve is electrically controlled, so it obviously has some kind of motor or solenoid on it to actuate it. But that actuator is also controlled by some other system in the car, probably a computer, which in turn may decide how to set the valve depending on input from a sensor somewhere.

This means that either the actuator on the valve itself is being affected by the RF from your rig, or whatever controls the valve (e.g. computer/sensor) is being affected by it and sending the wrong control signal to it.

In the simplest case, it could be the actuator. Some of the RF from your rig is being rectified somewhere and turned into a voltage across the the solenoid/motor input. If that's the case, then you may be able to solve the problem by adding some .1uF ceramic capacitors between the valve actuator wires and ground. Ideally this should shunt the RF away from the actuator.

Another approach might be to get some ferrite RF chokes and just wrap/snap them around the wires. I'm talking about something like this:

RF Suppression Snap-On Ferrite Beads at DXEngineering.com: Snap-on Ferrite beads for cables .275-inch to ¾-inch diameter

If that changes nothing, then the problem may be on the other end, i.e. the computer or sensor. I'm not really sure how to deal with that. Ideally, the computer should be shielded to prevent RFI in the first place. If there is a sensor input that controls the idle air control valve setting, then maybe that's the part that needs RF bypass capacitors and/or an RF choke.

-Bill

 

[serrasalmus]

the computer is cased in a metal enclosure and it works in combo with the the other sensors (ie map and tps in this case i believe) ill have to order some of the snap beads when i get some extra money and try those and see if that helps. what about the stereo though?

 

[Captain Kilowatt]

Is the engine actually changing speed or just the tach making it look like it is? I had a car that when talking on SSB the tach would bounce around noticeably but the engine speed was unaffected. Since there was no real problem other than the wayward tach readings I just ignored it and all was well.

 

[serrasalmus]

no mine is actually increasing and decreasing the motor with the rpm gauge

 

[Robb]

If the ECM is in a fully-contained and grounded metal box and if yet you are still having RF problems; then I would suspect that you may need to put grounded shielding on all of the sensor wires leading back to the ECM. If it is the sensors that are getting conflicting info because of RF; then so will the ECM. It is only reacting to the info coming in; not necessarily going out.

 

[mackmobile43]

make sure your puck mount has a definite good ground to the body which would be bare metal to bare metal and that the chassis of the radio also has the same

Good coax goes along way to fixing some of these issues

 

[serrasalmus]

ok mac this is my puck mount, i took my drill and a wire wheel and cleaned the area where the mount is on the bottom, the connectors are solderd and heatshrinked

and i thought lmr 240 was a good coax read lots of views and it was recommended by almost everyone

i was playing with it today while i was waiting for the misses and the kids to get outa registering at the college and i noticed it only does it sometimes and not all the time, but it always comes thru the cr stereo

 

[Robb]

I wouldn't blame that coax for your trouble.
That's fine coax with some nice shielding IIRC.

http://www.timesmicrowave.com/products/lmr/downloads/16-19.pdf

 

[unit_399]

What are those wires to the left of the mount and where do the go? RF from the base of the antenna maybe getting into the electrical system there. You might try building a small box out of single-sided copper-clad pc board and use it to shield the antenna base. 73s.

- 399

 

[serrasalmus]

What are those wires to the left of the mount and where do the go? RF from the base of the antenna maybe getting into the electrical system there. You might try building a small box out of single-sided copper-clad pc board and use it to shield the antenna base. 73s.

- 399

if i member right its the wiring for the rear defrost and rear wiper

 

[DXman]

I would try one of these:
"Model 420 Series filters are heavily built deep notching Chebyshev designs and are ideal for interference cases where harmonic or spurious energy is either detected or feared, and a must for good station design."

Model 420

The one I am using works very good!
http://www.iceradioproducts.com/filtersrf.html#M420

Being it's a export and it can have RF issues, the filter might be the answer!

One more thing - why do you have that 'flat" braided wire going off to the other side? It can't be a grounding wire is it?

 

[serrasalmus]

i was told that to make sure its grounded good make a extra ground so i did...

 

[DXman]

That's correct, grounding is good. But, to long of ground wires are not good.

Rule of thumb is: stay at 6" or less if possible.

If it was me, I would eliminate that braid and connect it over by the door somewhere, connecting the roof to the side. This way it will have a better ground and do this on both sides.

 

[Robb]

Think I would shield the exposed coax wire at the bottom of that puck as 399 suggested a few posts back . . . shield the sensor wires to the ECM too . . .