Cobra 148 gtl/Inverted V antenna advice

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148gtl556
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Cobra 148 gtl/Inverted V antenna advice

#410100

Post by 148gtl556 »

After a year of listening to cb in my truck I have finally built a base station and have been trying to get out and do some DX'ing. I have a 1992 malaysia Cobra 148 GTL

and a home built inverted v antenna in my garage attic. Now I can pick up across the pond (scotland, ireland, germany, etc.) and places like texas and california regularly (I live on the east coast in delaware). However, I can't seem to get my voice out at all (there is not much local cb traffic in my area). Now I have a few ideas as to why but I'd like to know where I should start first so I will detail the setup a bit more.

The antenna I tuned with the built in swr meter and have what appears to be a good rating (12 awg stranded covered copper and chinese balun). The antenna is a little bit greater angle than 90 degrees, facing east/west. Now the ends of the antenna are only about 10' off the ground.

The radio is old and I don't believe it has been recapped. That task is outside my skill level (though putting the ERF-2030 does sound appealing). Still running the stock mic, and tested it, it is getting out to my mobile in the driveway.

Then there is the power supply, I just have the power leads running to a small mower battery powered by a trickle charger.

So what should be the first steps I take to improve this base station. I'm not trying to break the bank and buy a mess of gear. Would the antenna be the best thing to change first or get the radio recapped? Any advice is appreciated as I'm pretty new to this hobby. Thanks
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Re: Cobra 148 gtl/Inverted V antenna advice

#410105

Post by jessejamesdallas »

"Hearing" stations across the pond, and down to Texas and over to Cali is one thing...But getting your name called by one of those stations is something else!

Your radio is probably just fine the way it is to get your name called, as long as it works and sounds clear, so I wouldn't spend any money on it just yet.

Your power supply is questionable at best using a charger and lawnmower battery...That may work good enough to make the radio function, but other than using a lead battery inside which could cause battery gas fumes to build up, those chargers "can cause" static noise in your radios receive...So the first thing I would do is upgrade to a proper power supply.

Next would be the antenna...You say it's in your attic? Your going to need to get that thing out of the attic and up in the air...At least a 30' pole or tower would be where I would start...(higher the better)

As for the antenna itself...you didn't say what wave length you made it...(1/4 - 1/2 - 3/4 wave?)...again, bigger the better!...a 1/4 wave would be something along the lines of a 102" mobile whip antenna, and a 1/2 wave or bigger, would be more along the lines of what allot of guys use for base antennas...but regardless, it needs to be outside in the air away from obstructions like trees and buildings.

Once you get those issues taken care of, you will notice allot more people calling your name...Still, most will be locals...To get out to those stations hundreds, and thousands of miles away, your going to have to bump-up the power...Now this is where your bank account will start to take a nose-dive.

Now if this sounds like allot more than your willing to jump into right now, then you might want to think about a radio that has SSB channels...on side band, you don't need near as much power to get your name called, as you do with the AM channels...you will still need to get that antenna up in the air, but a stock ssb cb radio can shoot skip when conditions are right without the need of a bunch of power.

Some of those guys you hear in other States or Countrys are running anywhere from 200w's, to a 1000 watts or more!....If your listening to channel 6...some of those guys are running enough watts to light up the New York skyline...

And then there's Motor Mouth Maul over on the west coast who has this monster antenna that he could use to let E.T. phone home on... :-D
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Re: Cobra 148 gtl/Inverted V antenna advice

#410106

Post by 148gtl556 »

So as far as the power supply goes the charger does put some static on the radio but only when charging, not nearly as much as another one I have or my shoplights, this is rarely an issue with my current usage. The initial idea behind the base station was to have long range communications if there was a widespread/extended power outage, for example east coast power grid down for a week, to at least be able to get info from other areas, if not transmit, if cell towers went down. So is there a better option than a 120 V supply?

The antenna is around 102", built at I believe 106" and trimmed until SWR on the radio looked good. I do have a 20' pole not too far from the garage but I'm worried about the tree overhead. Any good advice on doing a tree install? I have pecan trees and don't think they would be too friendly to an antenna in them. I was also thinking line loss would be a factor and running a 25' coax would be better than 100' plus.

I have been trying to get SSB contacts on ch 36-40 LSB but no luck yet, they only way I have to check if I'm on frequency is my SW/MW radio and everything sounds funky on SSB on that. I was not hoping to reach the west coast or gulf coast, but I thought my antenna being low I could get some NVIS contacts. Maybe thats more of a HAM thing or those that I reach then skip over me?

So I guess I need an outside antenna higher up and possibly a better power supply, but the radio should be good? I need to do some local range testing. Any other more specific recommendations or thoughts are welcome. I'm 30 getting into this and I want to keep this hobby alive in the future.
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Re: Cobra 148 gtl/Inverted V antenna advice

#410107

Post by jessejamesdallas »

If you want to do some tree-climbing, I knew a guy who stuck a antron 99 up in a pine tree once...had the antenna mounted on a 20' pole, then wiggled it up in the tree till the antenna stuck up over the top of the tree, and then he used some some clamps like you would use to mount a pole to a chimney to secure the pole to the top of the tree trunk...no need for guy wires since the pole was attached to the tree in several places...That got his antenna probably a good 50' in the air or better!...Think he did run a ground wire off the pole to the ground too.

As for being worried about signal loss running 25-100' of coax...just use a good quality coax (RG 213 or LMR-400) and you'll be fine...I have a 50' tower, and probably over 100' of coax running back to my radio and if there's any loss, it's so minimal it's not even worth a second thought.
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Re: Cobra 148 gtl/Inverted V antenna advice

#410110

Post by 443 Arizona »

there are endless ways to build antenna's, :arrow: one thought came to me about your situation,,, a long wire antenna, look it up :idea: , also, keep in mind that no matter how hard you squeeze the mic key, its the antenna that makes all the difference :eek:
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Re: Cobra 148 gtl/Inverted V antenna advice

#410137

Post by 148gtl556 »

I finally got my first contact on the base station, I got all the way to Texas! So it does indeed work.

I have never heard of a long wire antenna for a CB setup, only for shortwave reception. I've been trying to figure out how to mount an antenna outside without it getting taken down by a tree, I may go with a A-99 mounted to the garage roof in the future. For now I like mine being out of the weather and concealed.

But my next steps are replace my 25' RG-58 coax with 50' RG-213 for a quieter noise floor and ability to run a new antenna in the future. Get a dedicated power supply and keep the battery as a back up for power outages, I didn't realize how cheap they are. And finally ground the case of the radio to a driven ground rod. Does anybody have experience with grounding the case? Does it make that much of a difference?

It might be a little while before I get this done but I plan to make an update in the future when I do.

73's
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