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Injector feedback in Icom 2300H but not Motorola Spectra???!

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J

Jongage

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New ham, still wating on my license (been three weeks now). In preparation I installed two radios in my truck 2003 Ford F250 6.0 Diesel.

1. Icom 2300H (Purchased new from Ham Radio Outlet)
2. Motolola Spectra (Old)

Both are wired directly to the battery both positive and negative. Both are using an NMO mount in the roof that I installed.
Both batteries are brand new.

Now the problem.

The Icom has alot of RF interferencewhile driving. Primarly coming from the fuel injectors. I have ruled out the fuel pump as the interference does not occur during the "key on" phase. There is no interference with the engine off.

I have zero AC ripple measured on the multimeter.

The Motorola does not have anything, it is clean both on the receive and the transmit.

I know that I am not the first person to have this problem. I have been doing atot of searching and it is a very common problem. I am working on solutions and will accept any help, however it got me thinking.

Why the difference in performance between the two radios?
Most of the complaints the I have read are from hams and public service parts. Not alot of complaints from ambulances for instance.

Is there a common design that motorola incorporates in its design that Icom and other ham compaines do not??

Thanks

JG
 
mmckenna

mmckenna

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Not sure about the design, but I'd expect the Motorola to have some better filtering.

I do know that I had a Yasue many years ago that picked up awful alternator whine when I wired both positive and negative directly to the battery. Moving the negative over to a ground bolt on the fender next to the battery took care of the issue. Might just be that simple, might not.
 
R

ResQguy

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Icom IC2300H List Price: $236.00
Selectivity
Wide
More than ±6kHz/6dB
More than ±14kHz/60dB
Narrow
More than ±3kHz/6dB
More than ±9kHz/55dB
Spurious rejection
More than 60dB

Motorola SPECTRA List Price (in 1996): >$2,000.00
Adjacent Channel Rejection
(20/25 kHz channel) 90 dB
Intermodulation Rejection
(20/25 kHz channel) 80 dB
 
12dbsinad

12dbsinad

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mmckenna said:
Not sure about the design, but I'd expect the Motorola to have some better filtering.

I do know that I had a Yasue many years ago that picked up awful alternator whine when I wired both positive and negative directly to the battery. Moving the negative over to a ground bolt on the fender next to the battery took care of the issue. Might just be that simple, might not.
Click to expand...

I would also recommend NOT grounding directly to the battery. Reason being, the radio's do not have isolated ground. IF something ever became disconnected between the battery and ground (the factory battery ground) your radio ground would try to compensate (because it's grounded thru the coax and/or mounting brackets), causing hundreds of amps trying to be pulled thru the radios and the small gauge wiring. Not a good scenario.

Anyway, the first thing I would do is see how the noise is being injected in the radio, either thru the DC power or the antenna. One way to do this is to power up the radio with a jump pack or seperate battery not tied to the truck. If it goes away with the truck running, it's coming in from the DC power. Start there.
 
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techman210

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I have seen two different Motorola radios installed in the same year/model of diesel trucks. One had bad interference, the other, none. Connecting the radio directly to the battery had no effect.

Very little noise was present when looked at with a voltmeter, but using the ocillioscope revealed nearly 1.5v of noise, the same amount at the battery and the DC buss in the vehicle. Only a Motorola noise filter would solve the problem. Another filter, while removing most of the noise, had no effect, as it didn't do much to filter out the noise under 500 hz which is what was affecting the radio in question.

Anytime you cure powerline or RF interference, its about 80% theory and 20% experimentation.
 
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Kitn1mcc

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you have a spectra now. is this for public service work if so you can't use the icom on the non ham bands
 
mancow

mancow

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The Spectra has a preselector in front of the receiver that is pretty much a brick wall to out of band junk.
 
J

Jongage

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Thanks for all the feedback. It makes sence that the spectra has a difference sensitivity db rating.
I will play around with the negative terminal and place it onto the vehicle body. I did have an instance on my other car were i disconnected that battery however the vehicle still had enought power to turn on the radio. I figured it out, it was drawing power through the radio that was hooked up straight to the battery.

Also yes I have the spectra for my volunteer fire department and the Icom for ham
 
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