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post #1 of (permalink) Old 12-18-2002, 10:20 PM Thread Starter
 
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some useless CB dribble

I had a few days off recently and finally got to a project that had been a problem for a while...a CB in my truck that received great, but people could not hear my tranmissions very far at all.

to cut to the chase, here are a few observations after borrowing a properly working SWR meter...my friend brought his over, and lo and behold, I was not a total dumbaxx, my SWR meter was not functioning correctly.

my setup is this, radio shack $40 cheapie, 1 4" fiberglass whip or 1 radio shack "off road" whip (about 56"), and standard RG58 cable.

I mention two antennas, because I thought if I bought the longer whip that would solve my transmit problem. It didn't. So I set after my problem.

My antenna is mounted on the rear tire carrier. First thing I checked was the ground it was getting to the body....VERY IMPORTANT!! But no, mine was grounded OK. Once I had my friends SWR meter, we checked my current install trying each antenna....the 4' worked best, but something was still wrong as I was still transmitting in the "red" zone at about 2.3:1.

After wasting numerous hours on the internet, I decided that I may have blown something in my cheapie due to the high SWR, or I had a cable problem (length, short, cheap cable, etc). The cheapest route next was to go to radio shack and pick up some good RG8 cable and proper solder type connecters, in an 18ft length. This cable is about twice as expensive, and the connectors aren't cheap either. (the cable is still only like 60cents a foot.

I ran this cable just directly from the meter/CD to the antenna to test before burying, and guess what??? SWR with the long steel offroad whip was way better...just under 2:1. Still not great....I tried the shorter whip, and where last time it was better, it now gave the worst SWR. This new coax seemed to be matched to the whip better. The longer whip also gave the best SWR on the lower channels. Since I use 4 offroad, this is what I wanted.

Hmmm, still not a great SWR though. For the heck of it, I removed the hi lift from it's rear perch on the tailgate. It is verticle and about 12" from the antenna...Guess what....SWR goes down again.

I then removed the rear tire...SWR goes down just a bit again. So, I ended up having to move the antenna to the right on the rear carrier bar, to get it away from the tire a bit.

with all said and done and bundled up tightly, I now have a tuned SWR of about 1.5:1 which is decent. Amazing how a few little things can make a big difference. This should make a huge differnce in my ability to transmit at distance.

FYI, I did try the hood mount that some of you may use. I think it still is the best place for ground plane and a slightly improved SWR. On my truck it seemed to bring it down to 1.3-4:1 but I just didn't want it there.

Besides, now I had a new project, where to mount the hilift now that it could no longer sit verticle bolted to the rear tire carrier. [img]images/graemlins/smile.gif[/img]
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post #2 of (permalink) Old 12-18-2002, 10:45 PM
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Re: some useless CB dribble

interesting! I've had good luck with my 4' Firestik II on the tire carrier bar with their "no ground plane" kit. I talk to truckers on I40 all the time and I've talked 4 miles over a ridge before (5 watts), so it gets out. On the Disney trail run I mentioned to OzarkJeep that my "antenna warning" light came on occasionally and he put an SWR meter on it, which showed an infinite reading. I'm not sure how an SWR meter works, but I'm guessing it's because I dont have a closed loop in my coax (shield is not hooked to anything in the NGP kit). Logic would tell me that the radio's SWR sensing circuitry is similar to the meter's, so I guess it's always going to seem like I have a problem with this coax/antenna setup. Oh well, the sucker gets out and receives great, but I really need a stiffer spring cuz that 4' whip gets to whipping the living shlt out of my top any time i leave the asphalt! It's worn a white spot on there, which I dont mind, but I have to think that is bad for the fiberglass in the antenna.
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post #3 of (permalink) Old 12-19-2002, 06:00 AM
 
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Re: some useless CB dribble

i just finished putting my cb in last weekend and am going to take it to the cb shop to check it out. i drilled my rear bumper on the drivers side and put a 4'er on it the man at the shop can tweak it out he did a hand held for my years ago and got 14 watts out of it ,i didnt think of putting it on the tire rack would have gotten my higher
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post #4 of (permalink) Old 12-19-2002, 09:47 AM
 
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Re: some useless CB dribble

I put a tennis ball on my steel whip to keep it from beating the sh!t out of the back of the truck. An old trick that works. And the ball doubles as a toy for the dog! [img]images/graemlins/grin.gif[/img]
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post #5 of (permalink) Old 12-19-2002, 04:02 PM Thread Starter
 
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Re: some useless CB dribble

You mean he tweaks the CB right? The ouput (legally) of the CB is 4 watts. I'm an electrical dummy, but I really think there is no way the antenna changes that. However, what I was speaking of above is that unless you have a perfect match with your antenna, the 4 watts output is usually reduced by some percentage. As long as your SWR reading is at or below 1.5:1, the percentage loss is very small. From 1.5-2:1 is increases dramatically. Still ok, but not great. Beyond 2:1 you should not really transmit because the loss is large, your tranmit ranger very short, and it can damage your CB.

Usually 1.5:1 is considered fine. It becomes increasingly difficult to get results lower than that, which is why most "experts" agree on the 1.5 and that spending lots of time trying to reach 1:1 is not worthwhile. Even if you got there, the added transmit strength is minimal. It is the numbers larger than 1.5 where working on tuning the antenna becomes critical.

Does your CB shop know where you placed the antenna? I tried that awhile without much luck, they may recommend the carrier or the side of the front hood.
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