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[N4MU]

I just installed an FT-1900 in my 2011 F-350 diesel. Was looking forward to some casual use as I don't use the vehicle much. After the install, when I did turn the ignition on I was very surprised to have quite a mess of spurious signals over several programmed frequencies...not all, just some. Strong sigs too in some cases. The radio works fine and if the repeater is stronger than the spur of course it is fine or at least acceptable...I will probably remove the radio and use it indoors unless we have a wizard out there who has been there/done that. Here's the status (to save a lot of expected try this replies): 1. Noise NOT on DC line; radio is wired direct to a vehicle battery, tried ferrites and even wired radio to a completely separate small gelcel with short jumper on dash; no change. 2. Relocated wiring; no change. 3. Disconnected roof mag mount antenna...Noise Gone! Of course that leaves me with a "Catch 22". IOW, So far as I know, the noise is coming in from the antenna. Moved antenna to adjacent vehicle and noise decreased but was still rather evident. Turn off key/ignition and after vehicle computer apparently goes to sleep all is perfect! Turn key on (only to start - engine on or off makes no difference) and noise instantly reappears. Any suggestions from one who may have had the same thing? Oh...I'm keeping the truck...radio or not.

[K0BG]

First, the Ford truck in question does have 3 B-Cans (body LANs in other words). The harmonics spread clear into the UHF spectrum, but most of the time they're not bothersome. However, you're using a mag mount with not clear connection to the body, save for the coax shield. This allows the outside of the shield to be part of the antenna, so it picks up all of the spurs from (mostly) inside the vehicle.

Find a mix 43 or mix 31 ferrite core, at least 1/2 ID, and wrap two or three turns of the core through the core, close to the antenna. If the spurs are reduced, you'll know that the answer is to drill a hole, and mount the antenna permanently.

[N4MU]

Thanks (AGAIN) Alan! I will try that. I have another large ferrite (31 I believe) that I used with my Tarheel when it was on the vehicle but never "mobile" - just stationanry (Yes, you helped with that too!). I can wrap at least 4 or 5 turns at the antenna and see if there's a reduction. If so I have no problem with doing a permanent NMO. I'll let you know what happens. I also have what's left of my Breedlove Tarheel mount so maybe I can also "test" using that as a base for the NMO antenna. Thanks!

[K0BG]

Five or 6 turns isn't necessary. Remember, a ferrite choke, like any decent current balun, is a tuned circuit, and a specific number of turns ib partly based on the frequency bandpass.

[N4MU]

10-4! (Oops!) Got it Alan. Will advise, Thanks!

[N4MU]

UPDATE (Alan): (LOL)
I rigged a 20" section of 5/8" all-thread on my existing Breedlove truck bed lip mount (that served well for the Tarheel antenna...but never in motion or with engine on) and put a right angle NMO mount on the top by a clamp to the all-thread.  Basically an elevated, grounded mast section for the NMO 5/8 wave whip. The Breedlove is grounded at its' mounting position of course and also with a 1" wide flat copper strap to the wall of the bed at a tie down hitch point. NO change! Still hear the crud on 2 or 3 programmed repeater freqs at same levels. I then placed a 1/2" I.D. mix 31 core at the antenna lead (within just a few inches of base of antenna NMO connecter and did a 3 wrap...NO change!
Looks like the only way I'm going to get rid of these spurs is to try to drive at warp speed...oh maybe 1.1 mach and outrun them.
I have no more ideas. Do you? BTW, there are a lot more serious problems in the world...I admit. Oh well...

[K0BG]

No matter what you do, if the RFI is within the bandpass, you won't get rid of it. Since I can hear it for myself, I have to guess. And that guess is, the B-cans.

[N4MU]

Yep! It's in and around 146 plus or minus...not everywhere but enough. In my delusionary state yesterday, just for a moment, I thought I would design a bandstop filter to get rid of the spurs. I was momentarily elated, "Yes! That would do it!" Then the "down-side" hit me! LOL
Thanks for helping Alan. Merry Christmas and a very Happy and Safe 2016!