jimrockford

I've looked all over for answers to a few questions but keep finding conflicting information. Can someone help straighten me out?

I bought the following:

• Cobra 18 WX ST II CB
• Wilson Silver Load FGT-3 3 foot antenna
• 12' RG58AU coax cable (both ends are PL-259)
• PL-258 double female coupler

I intend to buy (if I can find a place that sells them):

• Firestik SS174 hood mount (or equivalent - whatever I can find)
• Firestik Fire-Flex coax with PL-259/fire ring (the coax I bought won't fit the Firestik hood mount unless I buy an adapter, and I'd rather have the fire ring type of cable anyway due to the lower profile)

I modified my Cobra CB to fit in the dash of my '98 4Runner. Even with a right angle adapter, the coax stuck too far out the back of the unit to mount the radio properly. So I removed the antenna plug from the back of the unit and soldered a coax cable directly to the circuit board. It now fits perfectly and I have an easy way to check the SWR without removing the CB. The coax I wired in is about 3 feet long. I bought the PL-258 coupler to connect it to another coax that will run to the antenna.

Now the questions:

1. Does the length of the antenna cable matter?
2. Do I need to compensate for the 3 foot pigtail I wired into the radio?
3. If not, can I shorten the overall cable length so I don't have coax stuffed all over the place?

AzStorm

1.No
2.No
3.Yes

Its actually better to NOT have excess coax,especially since most people tend to coil it up which can create problems.

Youll see sites that reccomend 18feet,but you shouldnt have any problems with setting your SWR with whatever coax amount you actually need.

Make sure you use an external SWR meter rather than the radios meter.These tend to be a bit more accurate.

jimrockford

Cool. That's what I wanted to hear. Thanks for the reply.

AzStorm

Your very welcome.
There are several keys to having a good working CB.
Antenna (qaulity and type) and antenna placement are probably the biggest,followed by proper SWR tuning of the antenna and proper ground is essential.
I grounded everything.Bed to frame,battery to frame,cab to frame,and alternator to frame.This step is probably more work and expense than most want to tackle but it was crucial for my set up since I run power.
Let me know if you have any more questions.

TStango

Did you notice a huge reduction in noise when you added all those grounds?
At times I can hear my alternator whine over my radio and I would like to fix that. Right now I have my firestick mounted part-time to the TJM bumper with a quick disconnect. I would like to relocate it permanently off the back of my rig. So when I do get around to it, I want to do it right.

AzStorm

There was a slight reduction in ignition noise but this works better.
http://www.partsexpress.com/pe/pshow...number=265-047

The front mount,close to the ignition source is probably the cause of the ignition noise.

What most fail to realize,when mounting the antenna on the rear bumper, is that the signal radiated from the antenna will reflect back through the antenna if placed close to the body of your truck.Most dont mount the antenna high enough.This can and will,whether immediate or eventual is dependent on numerous conditions,lead to the finals in your radio to burn out.It is also not the best way to get the most transmit and receive out of your radio.
Antennas are designed to radiate RF energy.The more efficient they can do this the better.It also makes for setting the SWRs a good bit easier.

Locating the antenna on the back of your rig would make the antenna somewhat directional with most of your transmit power reflecting from the front of the vehicle.If mounted on the right rear power or signal will be strongest towards left front of vehicle,on the left rear it would radiate stronger towards the right front.
I have found that an antenna works best when placed at approximately the center of the vehicle and as high as possible.
When using a 4' firestick,which are nearly indestructable,you could use a spring on the mount to protect the antenna from tree branch hits etc..

Hope this helps

TStango

It does. I really appreciate all the info. Thanks for the link too. I might have to try that filter.