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Kc8gpd
Junior Member
Username: Kc8gpd
Post Number: 12
Registered: 2-2004
| | Posted on Wednesday, July 02, 2008 - 9:52 am: | 
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1st. I bought a stereo amp install kit. 4ga. wires, power distribution blocks, inline fuse etc.
I will be running a stock 40ch CB, SVA w/amp(got FireCpt809's old setup) , 2 motorola amplified external speakers(one on sva, one on cb), and a SWR/Watt meter for 27MHz.
my question, should i run negative to chassis or direct to battery? with this equipment(the sva has the 45w amp, have not decided on using it or not) should i run off the battery positive or the fuse panel in the cabin?
besides RFR to passengers(should not be a problem at 5 Watts) what are the problems with mounting a 1/4 wave vhf whip to the hood lip with an L brack as opposed to drilling holes for an NMO mount in the roof?
object of install is minimum holes or damage to vehicle interior.
I have two CB's available. a Cobra 75WXST and a Uniden PC-?? (similar to a cobra 29).
uniden seems to fit a din bracket.
here is a pic of a Saber Vehicular Adapter.
http://gallery.batlabs.com/portables/sabmva.jpg |
Hotwire
Senior Member
Username: Hotwire
Post Number: 2537
Registered: 1-2005
| | Posted on Friday, July 04, 2008 - 9:13 pm: |
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With my own setups I run the amps' positive to the battery and negative cable to the chassis. Use the shortest length possible.
I run the radios' negative and positive cables to the battery with the shortest length possible.
ANy positive cables that run to the battery should be fused at the battery for safety purposes.
The reason for using the shortest possible negative cables is important. The longer the negative cables get to 9 feet the more they will act like antennas. They will actually radiate rf causing all kinds of problems. This goes for external speaker wires as well. Cut them all down to the size you need. You can always add more length later if needed.
As with any antenna mounting it on the vehicle roof is best, it is up higher and will radiate in an omni-directional pattern.
Mounting on the hood lip will cause it to radiate in a more directional pattern behind the vehicle more so than the front. May also pic up more engine compartment noise.
KEEP IT REAL!
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Tech237
Moderator
Username: Tech237
Post Number: 1020
Registered: 4-2004
| | Posted on Saturday, July 05, 2008 - 11:57 am: |
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Run both positive and negative to the battery - it helps to reduce potentilal problems from a bad earth. Remember if you run it to chassis and then rely on the battery-ground connections, that adds in another connection that can fail and cause trouble. IN fact if you look at the manufacturers recommendations they all recommend running cables directly to the battery.
With VHF, always mount anennas as high as possible. A 1/4 wave antenna mounted on the fender or hood lip is going to next to useless,as it will be sheilded in most directions by the cars body. If you don't want to use a thru roof mount, then (and I tremble at saying this as I really hate them) use a roof mounted magnetic mount. The reason I hate mag mounts is simply they are not as efficient as a properly installed thru roof base due to the fact that the mag mount relies on capacitive coupling for ground.
An example I can give, is while testing several antennas on my mobile for my daily 100m commute, I did borrow a mag-mount 5/8 wave 2m whip and whereas it did improve signals over the 1/4w thru roof mounted antenna it was also more susecptible to noise and interference from all sorts of things, including the lit dot signs the DMV use. When I replaced it with a 5/8 wave antenna on the thru roof mount the noise and interference problems disappeared and I got better signal coverage as well.
Another option, would be use a lip mount on the top of the hatch, but be prepared for some directionality if you do.
Simon
Tech237
N7AUS
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Kc8gpd
Junior Member
Username: Kc8gpd
Post Number: 13
Registered: 2-2004
| | Posted on Thursday, July 10, 2008 - 8:22 pm: |
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i'm thinking about popping snap on ferrites on the power leads to battery.
this should kill any potential RF problem from the power leads should it not?
I don't know if you can find a pic of it, but i have a 1992 Nissan 240sx with sunroof and hatchback.
also will i have any problems with ground loops running a ground strap from the radio to car chassis?
I tried contacting the Local moto Dealer for install services, but never heard back from them.
guess they have their hands full with county contracts and don't want to bother doing ham/cb installs.
the local car stereo guy does not do cb/ham installs either. |
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