I haven't retested the SWR yet, mainly because there is some amount of stuff
I have to take apart to get to the back of the radio. Then some stupid
neighbor comes over "WHOA MAN You got your car all apart!!!" and starts
wigging out sigh. And yes, I have committed the evil sin of running off
the car's power, my Kenwood CD player picks up AM without a hint of noise
from the engine, so I always declared it clean enough. However, I know
Nissan recommends running straight off battery power. I already recycled
some nice 14 gauge wire from work, and have a hole in the fire wall and some
fuse holders and a relay all sitting there (so the radio can be shut off
with the ACC), waiting to be soldered together. I'll have to try putting
those in this weekend. Right now the way it is the noise added is small, and
only transmissions I have to strain to hear in the first place are getting
drowned out. However, even with reasonably strong reception the annoying
part is that it noise mixes in and creates a very annoying tone in the
background.

For RF cable I am using mil-spec RG142. The original buyer paid about
$200/foot for it, and I acquired it at highly significant discount. Before I
just had some Tandy RG-8 stuff in there that I acquired at a ham fest and it
worked quite well but i decided i could do better. The Tandy wire I put in
originally was about 18f long or so. This is because I believed some tall
tale about coax cable length and resonance frequency when I installed it,
however I haven't seen anything confirming this theory beyond the CB world
so I dumped it and used the shortest length of RG142 possible. After
replacing it I measured the SWR and antenna field strength, and even after
tweaking the K40 inductor the SWR went up slightly and field strength went
down slightly. RG142 with its dual layers of brayed and foil shielding,
silver coated center conductor and reduced length should have increased
antenna performance, so im not sure why that happened.


"Gary" wrote in message
news
Just wondering how you can possibly 'retune' the antenna without knowing
where the swr is at any given time?

I am assuming the radio is wired directly to the battery with fuses on
both positive and negative? You certainly wouldn't consider running the
radio off of the car's auto electric system, right?


Zombie wrote:
FYI, the antenna has a tunable tip, and i eliminated about 90% of the
noise
by retuning the tip. Havent checked the SWR yet though.


"Zombie" wrote in message
...

Hey guys I have a problem with alittle noise from the fuel pump and a
lot

of

noise coming from the ECM on my 95 maxima. I hope someone can help me
out.

Here is the deal: Uniden CB radio. I have a 3' K-40 mounted in the rear
quarter panel. When I switch on the ignition, engine on or not it floods
with noise. I turn off the ignition, after 2 second delay the noise
stops.
If I dont have the antenna connected i get no noise. If the only the
positive connecter of the coax is on the radio then i will still get

noise.

I measured the resistance between the co-ax ground and the radios ground

and

got 90 ohms, between the radio ground's and the negative terminal of the
battery its about 2 or 3 ohms.

The antenna has a solid ground connection to the chassy, and under the

hood

i have a 4 gauge cable bonding the negative terminal directly to the

chassy.

This might make it seem like all the noise is coming from the antenna
side
of things, but if i use my handheld CB on AA battery power there is
virtually no noise picked up. If its powered by the cigarrette lighter

then

noise comes flooding in. This makes it seem like its coming from the
power
source.

I get zero noise from the AM radio in the kenwood CD player, which is on
a
noise filter anyways. I tried connecting the CB to the same power source

and

it didnt help.

Has anyone had a similar problem?