Hello SpakySKO:
You are experiencing noise problems a lot of guys have. Some just live
with it, and some try to cure it.
With a properly installed radio system, and good radio with a Noise
Blanker the noise should be at a livable level.
EMI (Electromagnetic Interference) is being experienced more and more
with new electronic devices.
In order for EMI to exist there must be three things, A noise generator,
a path, and a receiver.
Most of the times it best to reduce or attenuate the noise at the source
or noise generator. Or then break the path, then filter out the noise at
the receiver. In that order. But thats not always possible or particle.
I had a 1989 Nissan truck that everything caused noise in my radios. A
fuel filter in the power wires at the gas tank helped some. Shielding
the ignition wires also helped. But nothing I did was the total answer
that got rid of all the noise. Connecting the fender battery ground to
the fire wall and hood was also a help in reducing the ignition noise.
Everything I did helped reduce the noises a little but again nothing was
the total fix to remove the noises.
The muffler pipe was grounded about 12 inches away from the exhaust
manifold, the radios had a direct connection to the battery, both
positive and negative. Not having the radio ground wire going straight
to the battery is asking for noise troubles.
But the greatest help was a Heil DSP (Digital Signal Processor) Speaker
that reduced the noises significantly. I could here the local big base
stations all most 50 miles away.
You will hear more noises with the poor skip conditions, as compared to
the good skip conditions, when all the big boys are out there on the
channel.
Also remember that the low end radios don't have all the neat-o noise
reduction circuits in them. Comes down to if ya want to play ya got to pay.
Here is a book written on EMI or RFI:
http://www.arrl.org/catalog/6834/
Hope this helps.
Jay in the Mojave
SparkySKO wrote:
So my results with a Cobra 75 with just soundtracker had negligible
results versus my fuel pump noise. So I went and bought a Cobra 29 with
ANL, Noiseblocker and SoundTracker. With a base noise of S0 and S3 when
I start my truck, with ANL, Noiseblocker and ST turned on, the noise
dropped from S3 to S2. Although the volume of even voices sounds a
little muted, so the signal to noise ratio was improved a little, but
not completely.
Previously, I had blower motor noise from my AC, which went away when I
bolted an antenna mount onto my fender (When I was using the Midland
1001, Uniden 510, Cobra 75). However with the Cobra 29, the noise came
back. All the radios have used the same antenna mount and wiring
(straight to the battery, also have tried the bare metal where my
transmission shifter comes up from the floor, i'm able to use this for
a DC ground).
I tied of a wire to bare metal (confirmed it's a DC ground) and touched
all of the screws on the radio, no change. If I touched it to the
faceplate for some reason it sometimes changes the noise a little bit
sometimes, but not much. I've also touched this wire to the ground on
the antenna cable, and also tried grounding the antenna mount again. No
change.
Interesting to note that although the S meter drops with NB on, the
squelch setting seems to want to be in the same spot.
Also interesting to note, my portable shortwave radio which can do CB
frequencies, does NOT pick up the blower motor or the fan noise however
it DOES pick up the spark plug noise.
RF or not RF.!?!?!
I did check my fuel tank, and it is metal (I thought it was plastic). I
wonder if this can made to act like a faraday cage? I work in a
wireless labratory with UHF (2.4ghz, unfortunately nobody else is
really radio savvy, especially with HF), and we have rooms made out of
copper screen that is electrified ( i believe ), and no RF comes in or
out. Of course all the powerlines also need to be filtered.
Although I guess if the noise is coming out from the wires, it won't
make any difference.
I'm going to probably return this Cobra and get the Midland 1001Z again.