RFI in my cruiser (1 Viewer)

[Miescha]

I've been working on this Radio Frequency Interference (RFI) noise problem for about a week, talking with Alan at K0BG.com but I thought I would post here as Alan has no experience with cruisers and you all do

In short, the High Frequency (HF) bands from 0-54mhz transmit and receive crystal clear with great range. However, the Very High Frequency and Ultra High Frequency (VHF/UHF) bands from 100-500mhz and up transmit crystal clear and range seems correct, but the receive has a low level static that doesn't break through the normal squelch setting, but definitely is heard once a channel has transmission coming through.


I had my Icom IC-7000 installed in my 2002 Yukon XL Denali using a dual band Larsen NMO 2/70 for VHF/UHF (2 meter is the ham band that ranges from 144-148mhz and 70cm is the ham band that ranges from 420-450mhz) and a dedicated Firestick for 10meter (ham 28mhz) and interchanged with 12m (ham 24mhz) , 20m (ham 14mhz), 40m (ham 7mhz) as needed. The IC-7000 has two antenna inputs, so I keep the dual band Larsen on for the VHF/UHF bands and add the Firestick for the HF bands.

I moved the entire setup to the cruiser about a week ago. I left the Denali setup for an easy move back, but I used identical coax in the cruiser (Larsen NMO to Amphenol soldered PL259 for the Larsen and Firestick Firering to soldered Amphenol PL259 for the Firestick). I moved the actual coil and whip over to the cruiser and put a rain cap on the Denali NMO. The Firestick is on a quick-disconnect 3/8" x 24 stud on both vehicles. The Firstick is on my front ARB bar, which I spent a lot of time getting a very good DC ground and bonded with 1/2" braided strap to get a solid RF ground. The ground (image) plane remains poor - relative to a hole drilled in the center of the roof, but is adequate. There are no problems on HF anyway, so it is good enough. The Larsen is on a Larsen hood channel bracket on the PS about mid-way from the cowl to the front edge of the hood (same as the Denali).

I purchased a second Icom power cable from Ham Radio Outlet hamradio.com ($$$$ ouch) and ran it directly to the second battery on the cruiser (just as on the Denali).

I set everything up and the HF side (Firestick) is working great, just as in the Denali. But the VHF/UHF Larsen side has some minor RFI only when the cruiser engine is turned on. Its not that bad, in fact, but for seeing it on the main display I don't think I would have initially noticed it. It is below the squelch level I normally use. When I start the cruiser, the front display meter bounces from a low of 4 to a peak of 9 and an average of 6.

If I disconnect the HF antenna line, no difference on HF or VHF/UHF. If I disconnect the VHF/UHF antenna line, HF remains great (no surprise) and the RFI disappears (not really a surprise there either, I just wanted to make sure it wasn't coming in the power feed or the front end).

I've done a fair amount of bonding using 1/2" braided straps: two on the hood (one each side by the hinges); one on each of the four doors; I haven't done the rear hatch or tailgate, but I suppose I could. I have a single strap on the exhaust near the resonator.

Here is my suspicion: My cat got banged up pretty bad while wheeling this past weekend. As a result, the Y-pipe is loose where it mounts to the manifold (I can hear an exhaust "gurgling" leak there), and I the bracket just after the rear cat is completely broken (I can also hear it rattling around). I suspect this seperation from the frame and vehicle ground is the source of my RFI - I'll try to get it welded and add another strap by this weekend.

I know moving the same setup from one vehicle to another doesn't allow for comparison (even from one cruiser to another), I just added the details above for completeness and so it is clear that this is not a radio problem.

Alan K0BG thought the source might more likely be ignition related, but I figured if that was the case at least one other cruiserhead would have mentioned a problem.

I recently did a major tuneup, so all my wires are new (factory OEM) and the plugs, cap, rotor, etc. . . .

Am I missing anything? The RFI isn't affected by the AC, cruise, or stereo. The Digital Signal Processing (DSP) Noise Reduction (NR) on the Icom does make a marked improvement, but now that I see it on the display I know it is still there (I CAN also hear some static on the VHF/UHF stations that was not there in the Denali). The Icom noise blanker (NB) which would normally reduce or completely suppress alternator whine, has no affect on the RFI.

So, any thoughts from the cruiser hams?

 

[Vitesse_6]

Im not up an all the jargon
When I first installed my icom in my 80, There was a noticeable wine on the radio, Mine varied with the engine speed, I installed a filter near the radio and all is well.
If this isnt quite what you are looking for, Im sorry, Its been a long day.
Good luck!

 

[Miescha]

Unwanted noise in my Icom Ham radio when installed in the FZJ80 Cruiser

I welcome all ideas!

I think I have it under control, I was mostly thinking out loud and figured it wouldn't hurt to start an RFI thread for future reference should anyone else run into a problem (RFI = Radio Frequency Interference - basically any unwanted noise in your radio that shouldn't be there).

From your description of your previous problem,
it sounds like you had RFI resulting from alternator whine (a common RFI source). You didn't mention it, but I would guess you were using a mag mount antenna, but I'll wait to hear and I hope you'll post and share as I'm always curious as to the source of RFI in the mobile environment.

Also, installing the filter as you indicated will not solve the problem, but only mask it. If the problem is only on receive, that's probably sufficient. But alternator whine usually shows up on the transmitted signal also, and the filter may not stop that or if it does, you will likely experience a reduced output level. Still, if it works, I'd probably stay with it - so I'm definitely not knocking your solution, just thinking out loud again for anyone else who happens upon this thread.

As for my problem, it doesn't vary with the engine speed or any other electrical motor that I can find. I've pretty well ruled out alternator whine, and despite the leanings of of Alan K0BG, I don't think it is ignition noise either (but I'm no expert and Alan K0BG definitely is). I'm hopeful that repairing the exhaust damage and maybe some additional bonding of the exhaust will resolve the issue. Again, I'm mostly thinking out-loud in case someone else has some experience that triggers a resolution I may have missed. Also, I figured going through the possible trouble-shooting points might help others in the future who happen upon this thread.

I should have avoided the jargon as it is not helpful to others who find the thread - sorry about that. I tried to change the title to help others find the thread and its topic, but it doesn't seem possible. I'll go back and add some explanation in the original post to clarify some of the jargon.

 

[Vitesse_6]

Thanks for the edit

Here is my parts list for install on my 80...
Icom 2200H, mmc150(Maxrad 2 meter) antenna, L bracket, #1250 NMO cable w/ molded PL259

Yes, Im sure using a filter on the power cables will reduce the output, But its mostly for trail use, Ive built an antenna for the house for better reception.

Dont worry about the use of the jargon, I need to learn it myself.
Again, Good luck!

 

[rusty_tlc]

Have you inspected the grounding from the engine/alt to the frame? The point where the wire connects to the frame is often dirty and cleaning it will help eliminate many RFI problems.

Even though you don't have the noise on one band and do on another don't count out ignition as a source, the radios internal filtering may block noise on on one band and pass it on another.

 

[Miescha]

Have you inspected the grounding from the engine/alt to the frame? The point where the wire connects to the frame is often dirty and cleaning it will help eliminate many RFI problems.

Thanks - I'll double check this, but I have two new 2/0 grounds from the engine block back to each of my Optima batteries. I also added a 2/0 ground from the engine to the frame.

I do think I will add one or two additional 1/2" braided straps from the engine to the body and from the engine to the frame to allow for RF flow - as the 2/0 cable isn't the best for RF which flows on the surface.

Even though you don't have the noise on one band and do on another don't count out ignition as a source, the radios internal filtering may block noise on on one band and pass it on another.

Good point. I really didn't know if the difference between the bands meant anything - I just wanted to add as much info as possible in case it meant something to someone more experienced.

However, the DSP Noise Blanker doesn't help with the RFI at all and my understanding is that it should if the source is alternator/ignition - does that sound correct?

If not, what is the fix for ignition-source RFI? Where do I even start given what I've already done and what I have planned?

Thanks!

 

[rusty_tlc]

Thanks - I'll double check this, but I have two new 2/0 grounds from the engine block back to each of my Optima batteries. I also added a 2/0 ground from the engine to the frame.

I do think I will add one or two additional 1/2" braided straps from the engine to the body and from the engine to the frame to allow for RF flow - as the 2/0 cable isn't the best for RF which flows on the surface.



Good point. I really didn't know if the difference between the bands meant anything - I just wanted to add as much info as possible in case it meant something to someone more experienced.

However, the DSP Noise Blanker doesn't help with the RFI at all and my understanding is that it should if the source is alternator/ignition - does that sound correct?

If not, what is the fix for ignition-source RFI? Where do I even start given what I've already done and what I have planned?

Thanks!

New grounds won't help if the existing alt ground is faulty, it will still act as a resistance between the alt and ground which will generate a voltage according to ohms law. A really bad connection will mess with all the electronics in a car. Ask me how I know.

To many grounds can be a bad thing. Depending on the placement you can create a ground loop.

In terms of bands, lets say the 2M FM band is 144MHz to 148MHz. The radio will have a band pass filter that will block everything above 148MHz and below 144MHz. any frequency between those two will be passed through. In practice most radios have an RX band which is much broader than the TX band. Each band will have it's own pass filter.

I'm not real familiar with DSP's in radio applications. Depending on how the processing algorithm is written it may or may not eliminate a particular frequency for the same reason a physical filter may or may not eliminate a particular frequency. That is it could be within the range of frequencies that filter accepts as normal, or it could be a harmonic of an acceptable frequency. (A Digital Signal Processor, DSP, is just a digital filter applied to a the signal after it has been through the A to D processor.)

 

[Miescha]

New grounds won't help if the existing alt ground is faulty, it will still act as a resistance between the alt and ground which will generate a voltage according to ohms law. A really bad connection will mess with all the electronics in a car. Ask me how I know.

I spent some time installing several additional 1/2" braided straps tonight including two more on the exhaust and one from the engine to the frame. Sadly, no change whatsoever So I'll definitely be looking into your suggestion on the alternator ground wire (is this the single large gauge wire coming off the top rear (cab) side of the alternator?).

To many grounds can be a bad thing. Depending on the placement you can create a ground loop.

Yeah, this has been worrying me some. I didn't know anything about ground loops when I was installing my dual batteries and extra grounds - it was way before I got my license. I find that many hams don't know what a ground loop is or why it is a problem. All the same, I think I should be OK b/c the grounds I added/replaced were from the primary battery to the engine block (the factory ground was much smaller than the 2/0 I was using for the secondary battery and I wanted them to match). These both go only from the battery to the engine block, so I don't think there is opportunity for looping. The third 2/0 cable I added was from the engine block to the frame on the DS at the point where the primary battery connects to the block. I believe I disconnected the small factory ground from the battery neg to the body, but I'll double check this tomorrow.

In terms of bands, lets say the 2M FM band is 144MHz to 148MHz. The radio will have a band pass filter that will block everything above 148MHz and below 144MHz. any frequency between those two will be passed through. In practice most radios have an RX band which is much broader than the TX band. Each band will have it's own pass filter.

.

This is a very interesting point. First, the radio has both an auto-notch filter and an adjustable manual-notch filter. I've not used either and really don't know the proper method of adjustment - but I'll be reading the manual as soon as I'm done typing. Second, I purchased the radio from HRO as a demo model from their Vermont store. I didn't know it when I purchased it, but the radio has a free-band mod performed by HRO. This allows the radio to transmit in the full range of its receive capability (0.3-200mhz and 400-470mhz) and all-modes. I wonder if this makes a difference.

I'm not real familiar with DSP's in radio applications. Depending on how the processing algorithm is written it may or may not eliminate a particular frequency for the same reason a physical filter may or may not eliminate a particular frequency. That is it could be within the range of frequencies that filter accepts as normal, or it could be a harmonic of an acceptable frequency. (A Digital Signal Processor, DSP, is just a digital filter applied to a the signal after it has been through the A to D processor.)

Yet another great point and one I too wondered about. I have no idea what logarithm is used for the DSP - the Noise Reduction is adjustable and it makes a difference is the level of the RFI but doesn't eliminate it at any point.

Thanks for the input - I'll definitely spend some time looking at the alternator ground this weekend. I'm starting to wonder more about the ignition system, but I have no idea where to start. I was really hoping the braid straps on the exhaust and engine would make a difference.

 

[mrlocksmith]

I have the same problem pn my VHF RiG. I am using a mag mount, is there a way to put a ground strap on it?

Mark

 

[Miescha]

Your avatar appears to show an antenna on your front bumper.

Still, with regard to the mag mount, I'm not sure about the ground strap. I know mag mounts are a common source of ground loop problems, and DC ground problems in general (you can read more about both at www.k0bg.com).

It would be worthwhile to add a temporary ground strap to the mag mount just to see if the mag mount or lack of ground thereof, is causing the problem. I don't know what mag mount you're using or how it gets a ground connection, but assuming it is supposed to be through the magnet bottom to the vehicle, perhaps a strap from there to the frame just running down the side of the truck would be worthwhile as a temporary (not while driving) test to see if the RFI is resolved.

Should be easy to do and quick, so even if it doesn't work there is not a lot of time/work/money involved (assuming you have a long strap handy).

Good luck - and let us know what happens.

 

[groucho]

Similar problem...

Miescha,

I ran into this problem about 2 years ago, but since most folks around mud only focus on VHF/UHF, I figured posting something up might be a mute point.

I started out my Mobile HF schooling installing an Icom 706MKIIG into a 97 FZJ80. I connected it to a turbo tuner and a Hi-Q screwdriver antenna. When the install of the basics was done, I had almost no noise when the vehicle was off, and anywhere from S6 to S9 noise level when the car was running. My father has been a personal aquaintance of Alan's for many years, and so I corresponded with Alan to help the issue.

Firstly was the bonding using the 1" wide copper clad braid. I hit every door, the hood and both the upper and lower tailgates. I did not do the muffler. That produced very little if any reduction in noise.
Then I did Alan's next suggestion, which was to suppress the ignition wires (spark plug wires) RFI with 3M copper tape. This was a SOB, but I got it done. This made a noticeable difference from S9 at the top, down to S5-S6, but still reall bad.
Then my investigating went to using an oscilliscope to find the noise. All indications pointed to huge amounts of RFI egress from the Alternator and its curcuit. Alan spoke with me briefly about placing capacitors on the alt leads to help this. I have yet to do it (It is my father's cruiser).
The Icom 706MKIIG has many of the same DSP, NB functions as the IC7000, albeit less sophisticated (JEALOUS of you!), and they will blanket the problems but don't make them go away.

My cruiser has a Yaesu FT-857D, and i seem to have the same problems. No noise at all when the vehicle is off, but S5-S9 when running. Odd part about my setup? Sometimes I will tune in somewhere (40M for example last weekend) and with the car running and driving down the highway, all of a sudden the noise quits, and the sound is awesome! I don't know?

 

[groucho]

Some pics...

 

[Miescha]

Groucho - Thanks for the post and great pics! It is really nice to hear that I'm not alone on this issue. You didn't mention what year cruiser you were dealing with for your father and yourself, but from the pics it looks like we are dealing with the same engine (though no SC for me ).

As noted, I've done all the bonding using 1/2" braid (I don't think this will make a huge difference over 1" especially since neither of us noted any improvement at all). I do have two straps on the hood - one at each side next to the hinges. After yesterday, I have a strap at the rear of the exhaust just before the resonator and another at the front just after the Y-pipe before the first cat. Again, no difference at all. I also added a strap on the front ARB even though I removed all the powder coating from the inside of the mounts where it slides onto the front rails to make sure there was a good DC ground - but I can't find anything to verify that the RF will flow across the surface of the ARB given the heavy powder-coating. All the same, the extra braided strap made zero difference - my RFI is still bouncing the meter from S4-S9.

I also disconnected all the antenna feeds that were coming through the PS firewall as they were routed next to (or even against) the ECM in the footwell. I ran a new coax down the outside of the cruiser on the DS and tested it with a variety of antennas using both the ARB mount and a hood-groove mount. No difference. I feel this huge amount of time was not completely wasted as I'm pretty sure now it is not the ECM causing the problem (and I'm OK to leave the coax routed nearby).

However, I'm not ready to give up on this just yet. At a club meeting Friday night (only Hams would schedule a club meeting on a Friday night) I was referred to a member that was not there but is known to have a $45k spectrum analyzer and the willingness to share it . So the plan is to connect with him sometime in the near future (hopefully this week) and run by his place to have my cruiser spectrum analyzed (sounds wierd). My guess is that the alternator and/or its ground is going to be the biggest source, but the plug wires may also be close (I really don't want to wrap them like Groucho as that looks like one heck of a pain). I say this b/c, not having an oscillascope or spectrum analyzer, I tried a low-tech method of connecting the vhf/uhf coax but leaving the antenna coil and whip off and then moving the NMO connector around various points of the engine and ECM. Oddly, I still recieved several strong local signals (local police dispatch for example and the repeater that is a few blocks away) but the zero RFI. But when I passed the NMO mount near the ignition wires there was about S3 and when I lowered it to the alternator (maybe touching it) it shot to S9. The ECM, cruise and various other things produced nothing. I know this isn't scientific, but that is what my guess is based upon. I didn't look into the fuel pump as a source, but now wonder if I should have.

Oh well, I'll keep you all posted so long as interest remains.

Thanks again to everyone for the suggestions.

 

[Miescha]

I just got off the phone and my cruiser gets spectrum analyzed tomorrow morning - whooohooo!





We now return you to your normal broadcast. . . . . .

 

[Miescha]

Just a quick update. I spent six (6) hours today with a local ham and his two (2) spectrum analyzers. We scanned the whole dang cruiser and determined the following:

1. The noise is radiated, not conductive
2. The noise is pulsed, not static
3. The noise is either the cap/rotor or the center wire, but definitely not the coil (ignition pulse either way).

So, for everyone that guessed ignition noise you were correct. Nothing coming out of the ECM, exhaust, alternator, or anything else in the engine or under the dash (except the 11m antenna coax that I forgot was on the DS under the dash and then got real excited when I ran the probe over it and the display went crazy ).

The individual wires to the six plugs showed virtually nothing when probed, and ditto for their connectors at the dist. cap. However, the cap itself showed high RF when probed on the top (where the connections are) but nothing when probed on the sides. The highest RF was at the connector for the center wire - but when I ran the probe down the wire toward the coil, the RF dropped and there was nothing at the coil itself. I placed several chokes on the wire but no improvement anywhere.

Remember, all the wires, cap, and rotor are new. The coil is not but that doesn't seem to be the problem. I also checked that the center wire had a tight fit - it did. Being new doen't mean it is not defective, I'm just pointing out the facts. So . . . at this point I guess I'll look into RF suppressing wires and an RF suppressing cap. The rotor is, in fact, an intentional spark-gap generator so I don't think I'll find an RF suppressing rotor (or cap for that matter, but I'll try).

As an interesting aside, we also connected the radio to an external battery outside of the cruiser (to rule out DC source noise) and connected an external mag mount antenna - no change in the RFI. We also tried putting the mag mount at various different points of my cruiser side-to-side and front-to-rear but still no change in the RFI. Next we placed the mag mount on the rear side quarter panel of the cruiser (making it a horizontal antenna) and the RFI diminished significantly to about S1-S2 pulsing - confirming that the RF was a vertical wave.

We also placed the external battery and radio in another vehicle with the mag mount on top of that other vehicle (which was parked about three (3) feet away from the cruiser) and the RFI was still there!!!! So then we took a brand-spanking-new-in-the-box IC-7000 of the other ham (really, the box was just delivered by UPS while I was there) and connected it to make sure it wasn't a bad radio - - - and it showed the exact same RFI and same level. We then checked the Icom 2820 that the other ham had installed in his vehicle (still parked about 3-feet away from my cruiser) and found ZERO RFI so we then connected the external mag mount antenna to his 2820 thinking maybe his installed NMO Diamond antenna wasn't sensitive enough - ZERO RFI still This is when the other ham realized that the IC-7000 is simply a more sensitive front-end radio as it has AM/FM/SSB etc. . . and the 2820 has only FM so it doesn't even pick-up the RFI being radiated by the ignition system.


So . . . back to work trying to find a new cap and center wire that is RF suppressing or at least another new cap and wire to make sure the recently installed items are not defective.

In the end, the problem is not solved, but I'm a lot happier just knowing what items are NOT causing the problem and that my radio is NOT defective and the antenna, coax, and mounting locations are NOT part of the problem. I'll sleep better tonight.

Cheers.

 

[groucho]

Fells good to find it, adds more frustration to see it is harder to fix...

I did the same thing with my borrowed oscilliscope. Since the alternator and distributor are fairly close to one another, I couldn't make the confirmation of either as being the culprit for my RFI. But it was definitely either ignition or charging that was the problem, so I am glad it is consistent with yours.

There has got to be a real way to shield the cap and center coil wire. It might be interesting to try different configurations. I wonder if it would be possible to make a copper "Hat" that is no more than a 5 sided box that goes over the top of the distributor with slots for the wires to pass through? I might give that a try.
Or some sort of use of some coax shield wrapping the distro.

I would really like to get my S-level down to S1-S3, it would be nice. Your information points me in the direction of suppression at the distro.

 

[Miescha]

I did the same thing with my borrowed oscilliscope. Since the alternator and distributor are fairly close to one another, I couldn't make the confirmation of either as being the culprit for my RFI. But it was definitely either ignition or charging that was the problem, so I am glad it is consistent with yours.

I would really like to get my S-level down to S1-S3, it would be nice. Your information points me in the direction of suppression at the distro.

I originally just used my 2/70 NMO coax as a probe by removing the antenna and just passing the NMO mount around the engine - wherever there was a strong RF signal I could see it on the bandscope of the IC-7000. I too orignally thought it was either the wires or the alt. But with two different spectrum analyzers, it is definitely the distributor cap and possibly center wire. I think any RF on the other six plug wires is just conductive from the dist. cap. That may also be the case with the center wire, but the RF was much stronger and wider ranging on the center wire so I didn't rule it out as the culprit. Thinking about how our cruisers dist. and rotor work (spark-gap generator) I think the center wire just gets more conducted RF than the other six plug wires - I don't think it is the source.

The dist. cap is actually going to be tougher to fix/shield. I doubt anyone makes a cruiser-specific RF suppressing cap so your idea of a box/trap or 3M copper tape is all I can think of. The IC-7000 actually does a terrific job of suppressing and filtering the RFI given what we were seeing on the spectrum analyzer. In fact, if I engage the Noise Blanker, Noise Reduction, and twin Band Pass Filters, I can get it to almost disappear. But I'd rather fix it than filter it

I'm also wondering if adjusting the timing (which I've never done) will make any difference. As I look at the FSM procedure, it seems I would need to rotate the dist. and that will adjust the timing - but I don't know how so. Does it adjust the rotor speed or spark gap or ?????

I guess I can just try it and see.

 

[NW Wheeler]

Reviving this thread, after a fair bit of searching there doesn't seem to be much on RFI, and almost nothing on RFI problems related to 12VDC powered fridges.

Have a Yaesu FT-2900R 2M, with a quarter wave mag mount (SWR good). When the ARB fridge runs it completely overcomes the squelch at max setting - very obnoxious. Have verified that the RFI is coming in through the antenna by doing the disconnect-antenna test. I can list the testing I done so far, but could it be as simple as the poor grounding situation caused by using a mag mount rather than a hole-in-the-roof mount? Before I buy another antenna am hoping to find out if the permanent mount is the cure.

 

[Fast Eddy]

I would consider the 'fridge the problem and fix the problem instead of swapping out perfectly good radio gear.

 

[NW Wheeler]

I would consider the 'fridge the problem and fix the problem instead of swapping out perfectly good radio gear.

Agreed, I have been working with ARB for a month and found that this is a known issue, although there isn't much on the web about this RFI caused by the fridge. They have been slow to supply a solution and I am leaving on a 3000 mile trip to CruiserFest in a few weeks and am looking for fix before I leave. Thought I would throw this out to see if someone had experienced and solved this already.