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1-7 of 7 messages
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IC-7000 with Engine noise on VHF/UHF but not HF?
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by KD0EIL on September 9, 2008
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I have an IC-7000 that I recently removed from my 2002 GMC Yukon XL Denali and installed in my 1996 Toyota Landcruiser (dedicated off-road exploration/rescue vehicle). The radio performance was simply amazing when installed in the Denali. It is a different story in the Landcruiser.
(1) I'm using a Larsen NMO 2/70 for vhf/uhf (which I moved from the Denali - so same identical coil & whip). This is mounted on the passenger side of the hood, mid-way front to back, using a Larsen hood-channel angle mount (I used the same mount and relative location on the Denali). FYI, as many of you may recall from past posts, I'm not opposed to drilling holes (and much prefer the better look and performance thereof), but a fully-loaded roof rack prevents it on these vehicles. For this antenna I'm using the Larsen NMO-K coax with a soldered PL259 "kit."
(2) I'm using a variety of dedicated HF antennas (10m, 12m, 20m, 40m so far) mounted on the front "bumper" which is a heavy steel ARB winch bar using an existing 3/8 x 24 hole. For these antennas, I'm using Firestick RG58 coax with a soldered PL259 that I already had in-place from a previous CB installation.
(3) Power is via the Icom DC power cord that came with the radio and is direct to the auxilary battery for both neg and pos (this vehicle has a three battery system - the battery in use for the IC-7000 is isolated from the starter battery, but grounded to the engine and frame using 2/0 cable).
(4) The radio is *not* currently grounded at the mounting location using the ground screw on the rear of the radio (I've yet to find an appropriate ground point near the mounting location).
(5) The head is remote mounted in the front of the vehicle near the factory stereo using the Icom remote kit - no issue that I'm aware. I have the Icom remote speaker mounted, but not currently connected as the audio level from the remote mounting location is plenty loud. I have the HM-151 mic connected to the rear of the radio as it reaches OK from the remote mount location, but I may move it to the head connection if I cannot locate an extension (I just prefer not having the cord connect at the head from a personal visual perspective). I don't know if any of these items are important, I'm just adding as much info as possible.
(6) I've done a fair amount of bonding on the vehicle using 1/2" wide braid, including two points on the hood (one on each side near the hinges), one strap on each of the four doors, one strap on the front bumper and one on the rear. I've also got one strap on the exhaust near the end of the vehicle. However, just prior to installation of the radio the catalytic convertors and a portion of the exhaust just behind the cats were damaged in an off-roading trip (hit by big rocks). The mounting bracket for the rear cat is completly detached from the frame and the front cat is pretty loose. Also, the connection of the exhaust Y-pipe to the manifold is loose. I don't know if the noise was present prior to the exhaust damage as the radio was not yet installed. I will be doing some welding repairs this coming weekend and I will add additional bonding straps at that time.
(7) The Issue: HF is crystal clear and by all accounts my transmissions seem fine and the distance I'm reaching is in-line with my experience.
However, on VHF/UHF, I see the display meter jump from nothing when the engine is off (on receive) to a peak of 9 and average of 6 when the engine is turned on. If I un-squelch the audio I hear only the normal static. On receive, everything has static but it is fairly minimal. I just know that none of the freqs I have programmed normally have static. On transmit, everyone indicates my signal is clear.
The noise blanker makes no difference in the receive static. The DSP NR makes a significant improvement (but it is still there).
If I disconnect the HF antenna line, there is no change. If I disconnect the VHF/UHF antenna line, the noise obviously drops out and I can see no pulsing on the display meter.
To be clear (no pun intended), this is not causing a huge problem on recieve as nothing breaks through the squelch at its normal setting - but the minor static is starting to bother me. There is no problem at all on transmit that I can determine and no problem on HF at all. Frankly, if I didn't see the display meter pulsing, I probably wouldn't notice it at all (even on the receive).
I first thought perhaps I did a poor job of soldering the PL-259. I had a few other club members look at my work and they all said I would be crazy to clip it off and do it again. After much agonizing, I clipped off the amphenol connector and installed a new one. I did not even re-use the reducer, though I was tempted after working hard to un-solder it just to see if I had a solid connection previously). FWIW, I followed the directions of K0BG precisely, even using nearly all the same tools (but lacking all the experience and skill :-). Of course, there was no change with the new PL259.
At this point, my only guess is the exhaust bonding. But it seems odd that the noise is only coming in through the VHF/UHF antenna and not the HF - and the HF has a relatively less-ideal DC ground and image plane, though possibly a better RF ground.
It may be premature to even ask prior to repairing the exhaust and bonding it, but I'm hoping something in the *extensive* description I've given may lead a more experienced reader to suggest additional items to investigate, just in case the exhaust repair and bonding doesn't resolve the issue (or there is another issue which I've completely missed).
Many thanks!
William
KD0EIL
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RE: IC-7000 with Engine noise on VHF/UHF but not H
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by K0BG on September 10, 2008
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You're seeing what a lot of other mobile operators see. The RFI does de-sense the radio to some extent, but it is usually minor. Why it is there is the question?
You might reinstall the whole works in an otherwise identical vehicle, and have no problems whatsoever. A lot of it has to do with how well things are bonded together at the factory.
The source is most likely the engine control system. You could find it with a spectrum analyzer, but that doesn't mean you can correct it.
I would bond the exhaust, obviously, but I'd leave the radio grounding as it is. Sometimes, grounding the chassis at a different point than the ground lead, can cause a ground loop to appear. It's sort of asking for trouble. As long as it works, don't fix it!
Alan, KØBG
www.k0bg.com
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RE: IC-7000 with Engine noise on VHF/UHF but not H
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by WW5AA on September 10, 2008
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Just as a side note....last week a friend stopped over with a RFI problem on his old mazda four wheel drive. As usual bonding the doors, hood and exhuast cut the problem in half. While fooling around underneath I noticed the emergency brake cable and touched a ground strap between it and the ground strap for the driver side door. Presto no RFI.
73 de Lindy
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RE: IC-7000 with Engine noise on VHF/UHF but not H
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by KD0EIL on September 12, 2008
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Thanks Alan and Lindy - I appreciate the help.
I repaired the exhaust and also added two more 1/2" braided straps to the exhaust. I added another 1/2" braided strap from the engine to the frame and from the engine to the body.
Sadly, there was no measureable change in the RFI. :-(
So I'm not really sure where to go next - I really thought the exhaust and extra straps would make at least *some* noticeable difference.
Another ham who also owns a landcruiser suggested I check the ground wire coming from the alternator as it was the source of RFI for his 2m radio in the past, so I'll look into that this weekend.
I don't have a spectrum analyzer or access to one (or the big $$ to run out and purchase one for one-time use :-) but after thinking about Alan's comment regarding the Engine Control Module, I realized that when running the coax for both antennas and the DC power, I went through an existing hole and grommet on the passenger side firewall that is used for the steering column in right-hand drive countries. However, this results in all the lines coming in at the passenger side footwell and they are all ultimately hidden behind the kickpanel there and resting directly against the ECM which is also located behind that same kickpanel.
I really didn't even think about this being a problem, and if I had I probably would have concluded that the cable shielding and sheath would be sufficient to prevent any RF ingress from the ECM - but maybe I'm wrong.
Does the ECM produce RF at that location, or is it more the entire engine control system? If it does or could, would having the coax against the ECM allow RF ingress?
My plan for a low-budget and low-tech test is to simply take another Larsen NMO coax and run it from the antenna to the radio along the outside of the vehicle and coming in the rearmost window. This will allow me to have all doors/hood closed while not pinching the coax but move it away from the ECM and see if there is any difference - but I won't have to unsolder the PL259 from the existing coax or pull it out of the firewall and possibly fish it back in if that isn't the source of the problem.
Any other ideas?
One more possibly important factor: as some of you may recall from other posts, this radio was purchased from HRO as an open box demo unit and HRO performed the free-band modification. I can't imagine this is a cause given that the radio performed flawlessly in another vehicle, but maybe it allows RF of a given range that it woudln't allow but for the modification and that range of RF simply wasn't present in the other vehicle.
Thanks all.
-William
KD0EIL
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RE: IC-7000 w/ Engine noise on VHF/UHF but not HF
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by KD0EIL on September 14, 2008
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Yet another update (I wish there was an 'edit' option for my previous posts).
After a bit more bonding with 1/2" braid - still no improvement. I also did a lot of low-tech testing with a new Larsen NMO-K coax kit: basically, I ran the coax along the vehicle as I moved the antenna to various points. It was not mounted anywhere save for the mount I already had at the hood groove and a vacant mount on the front ARB bull bar. No combination of coax location & antenna location seemed to affect the noise (S4-S9 pulsing).
I removed the coil and whip and noticed that the noise disappeared. So I moved the NMO end of the coax around a few different locations and found that some noise was coming in when it was near the ignition wires and quite a bit more when it was near the alternator (I also received several transmissions from strong local repeaters even though there was no coil or whip at the end of the coax!).
I decided to step-up the attack. I've made preliminary arrangements for a local club member to use their spectrum analyzer in an effort to find the source(s) of the RFI. I'll report back - hopefully with a definite source and resolution.
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Spectrum analyzed my vehicle today!
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by KD0EIL on September 17, 2008
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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 doesn'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.
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. I guess I could always try to make my own RF suppressing cap by covering the existing one with 3M copper tape and I guess do the same with the center wire - but that sure sounds time-consuming (as if I haven't spent enough time already :-)
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.
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RE: Spectrum analyzed my vehicle today!
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by N2RRA on September 19, 2008
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Just an idea!
I would buy some steel braided hose just the right diamter to slip it over the distributor cables and hose clamp at the ends. Then bond them to the chassis ground and see if you can shield them that way.
Maybe it will help!
73!
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