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Author Topic: radio noise and isspro gauge  (Read 709 times)
KF4STX
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Posts: 7




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« on: September 02, 2006, 03:26:10 PM »

I installed a Kenwood TMD700 in my 02 Chevy Silverado Duramax/Allison. Since day 1 I have had a signal that would give me s-4 noise with the squelch open. This signal would fully quiet the background noise for 3 seconds then disappear for 15 seconds. I determined that the noise comes thru the antenna. It would also show up as s-9 on my Icom IC91 when held close to the dash. It appears from approx. 139.000 to 149.000. Well after alot of hair and fuse pulling I found out the interefence is coming from my Isspro 3607 E.G.T gauge I installed on the a pillar. When the gauge is deenergized the interference goes away. My problem is how to fix? I installed torroids on the power leads, caps on the power, grounded the thermocouple, covered the control box with aluminum foil and a ground strap. Aside from buying another brand of gauge does anyone have any ideas? I need the gauge for towing.
Than you in advance
Lane
KF4STX
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KB1LKR
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Posts: 1899




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« Reply #1 on: September 02, 2006, 08:07:47 PM »

You've put ferrites (and capacitors) on the power leads, but how about the control box to gauge leads & the thermocouple leads? Are you using the right mix (43 for VHF??) ferrites? Is the antenna solidly grounded at the mount (some recommecnt sanding off the paint at the *inside/underdide* edge of the 3/4" NMO mount hole so the teath on the mount clamp get a good ground. It the antenna coax run adjacent to th econtrol box to gauge (or other) leads? Have you contacted Isopro?

On another note, how hot is too hot on a P/U diesel's exhaust?  
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K0BG
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« Reply #2 on: September 03, 2006, 05:59:49 AM »

This isn't the answer you wanted perhaps... but replace the gauge with non-electronic one. I might suggest you buy one from Banks Engineering.

You are not the first one to bring this to my attention, and although I don't mention it on my web site, it is in my RFI database.

Alan, KØBG
www.k0bg.com
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KF4STX
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Posts: 7




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« Reply #3 on: September 03, 2006, 07:13:24 AM »

Thank you all for such fast response.

K0BG I figured someone has seen this before. I think I will try the beads first and replace as last resort. Thanks also for your fantastic website on mobile installs. I almost read the whole site one day in prep for this install. That is probably why this is my only hiccup. I will keep you informed if it works.

KB1LKR  I am going to try the beads before changing the gauge. With the new diesels that use common rail electronic fuel injection there is a lot one can play with. But with diesel fuel containing more energy than gas one has to be careful. If one runs the engine stock there is no cause for alarm. But when someone like me can not keep from reprogramming the ECM one has to be careful. When I have mine programmed for "Fun Mode" I can not tow my trailer as enough fuel is being injected to raise the cylinder temp above the melting point of the aluminum pistons which is approx 1450 degrees F. So if I see the gauge approaching 1300 degrees I back off the throttle. Ther are lots of websites that cater to the diesel buff (thedieselplace.com for chevys) if you are further interested.
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K0BG
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« Reply #4 on: September 03, 2006, 07:50:55 AM »

There is one thing to keep in mind when using beads to control egress RFI. You should use the bead mix best suited for the RFI frequency peak, not necessarily the band you're using.

Alan, KØBG
www.k0bg.com
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KF4STX
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Posts: 7




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« Reply #5 on: September 17, 2006, 12:50:02 PM »

UPDATE
 I spoke with an ISSPRO engineer about the problem. He said he was also installing an APRS setup in his vehicle and experienced the same problem. He has brought this to the attention of the company and is working on it. He said the RFI comes from the leading edge or the output pulse from a volyage to frequency converter that is used for isolation. He also stated he tried the ferrite beads already with no luck. I am going to wait a while to see if they can fix the problem. For now the gauge is unpowered unless I am pulling a load.
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K9OMF
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Posts: 2




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« Reply #6 on: December 02, 2006, 09:17:09 AM »

I just installed an ISSPRO R3607TR pyrometer in my truck and found that it causes RFI in my VHF ham radio also. I looked at the DC voltage with a 100 mhz scope and there is not a trace of rf on the line. I did notice that the interference appears to be shifting freq on the 2 meter band.  I used an ht to listen on a different freq than the mobile rig and the noise was at a different time.  Using the ht it appears like the radiation is on the line from the amplifier to the gauge. Very difficult to trace for sure.  Has anyone explored this further?  If so, what has been the cure?
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KE7FIX
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Posts: 2




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« Reply #7 on: January 26, 2008, 02:52:30 PM »

Howdy,
I'd like to know if you found a solution, other than disconnecting or replacing your gauge? I also have the s-4  EGT noise and the gauges were installed in late 2007. Well, to be clear, The original set of gauges were installed in Sept 2007 all was well. The EGT gauge had a bad LED so it was replaced under warranty at beginning of January. It was shortly after that I noticed that there was a noise in the Yaesu 8800 so I wonder it the replacement gauge is causing the problem.    I get the S-4 static you mentioned as well as needle jumping up (EGT goes up and tranny temp goes down) when I key the mic  that seems to be influenced by the position of the antenna. When I attached a magnet mount antenna there was no needle jump. I didn't have the truck running so I don't know if the S-4 static was gone as well.  Hmm, now that I think about it, I installed a more permanent antenna (from mag mount to fender mount) so I wonder if that had an effect.  The coax now runs nearer to the control box and gauges than it did when I was using the mag mount.
I re-soldered the ground on both ends of the coax, with no help.
Thanks for your time in replying.
Fred
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K9OMF
Member

Posts: 2




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« Reply #8 on: January 26, 2008, 04:19:37 PM »

Hi Fred,
No, I never did find a solution. Isspro  ignored me, after all the gauges worked, so it's not their problem, at least in their minds.  Actually these days I seldom turn the 2 mtr mobile on so it's not a problem.  I mainly used the rig on my commute into work talking to a couple of friends.  Well I retired last summer so no commute now.

I did look at the 12 volt power lead with a o-scope and it was clean.  I am guessing that the interference is being radiated from the wiring between the amplifier box and the gauges.  Probably antenna placement and its coax routing will give the most bang for the buck.  It sounds like you have discovered that already.  I did not have much choice on my pickup for mounting the antenna, it is mounted on the left front cowl.  The antenna is only about a foot from the amplifier box, so what is what it is.
Best of luck, 73s
Joe K9OMF
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KE7FIX
Member

Posts: 2




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« Reply #9 on: January 26, 2008, 05:49:10 PM »

Joe, Thanks for the quick reply. Interesting that you and I have antenna mounted on the left fender and having issues with gauge noise. My antenna is about a foot or so from the front of the hood.  I really don't want the hassle of moving the antenna to another location (roof?), however... I'm going to ask some of the more knowledgable folks around here if there is a good method of RF shielding. I'm not sure how to isolate the situation to see if its RF getting into the gauge controller or the gauge itself.
Thanks again.
Fred
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