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Message |
    
Gonemuddin1
New member
Username: Gonemuddin1
Post Number: 1
Registered: 4-2005
| | Posted on Wednesday, April 06, 2005 - 11:38 am: | 
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Ok, Im running a 102" stainless steel whip that is mounted to the hinge bracket on my swing out spare tire carrier of a '94 S-10 Blazer, its basically like a bumper mount set up just about 3" higher than the top of the bumper. About 1.5' to 2' of the antenna is running in close proximity to a parallel section of the body. I checked my ground and it is good at 0.2 ohms. When i checked the SWR it was at around 4, and showing that the antenna needed to be longer. After adding a 3" quick conect it came down to around 3.2. In an attemp to lower the SWR further i machined a 3/4" diameter 6" long extension from brass rod. This has brought the SWR down to an average of 2.2. I am running a Cobra 19 Plus with an 90 degree coax connecter on the back of it, with 18' of coax to the antenna.
With all the background information provided my real question is how can I get my SWR below 1.5. I was thinking about trying to add a section of coax, becuase at 12' from ground to tip I dont really want to extend the antenna itself. What would be the best way to add the coax? Ive herd that each connection decreases power. Also I would prefer not to run a spring becuase i dont want it to lay down at highway speed, and I dont like the idea of it hitting my truck all the time. Any help would be much apreciated.
Brandon |
Rover
Intermediate Member
Username: Rover
Post Number: 152
Registered: 2-2004
| | Posted on Wednesday, April 06, 2005 - 12:15 pm: |
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Close proximity to the body. THAT is probably a clue. Adding and shortening coax does NOT "tune" the antenna. It *may* fool you and the system/meter into thinking it is matched. I believe you need to get the antenna away from the body. You said the antenna was at 12 feet total now. Thirteen six is the legal limit (like overpasses). I would add length up to 13'6" and see what happens, or get the antenna away from metal. Then if that works, you can fabricate a nonconductive bracket to attach to the luggage rack to prevent the antenna from leaning back.
I build multi-band HF antennas that, to most people, would seem to be heavy. They are often secured to the luggage rack via a long piece of
Lexan. This keeps the mast and whip in place and
there is very little lean-back. It would be very easy to extend the whip longer, or move it up higher, then make a bracket to hold the thing still, or at least mimimize the whip's flopping around.
If you feel the coax route is the way to go (and I wouldn't do this as fiddling with coax length is not *really* the way to match antennas), then one barrel connector in line is not going to make a substantial difference in your SWR. |
Marconi
Intermediate Member
Username: Marconi
Post Number: 420
Registered: 11-2001
| | Posted on Wednesday, April 06, 2005 - 1:30 pm: |
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Checked your ground and got a good .2 ohms, hey. Probably didn't zero the meter. You shouldn't have any resistance to ground. How and where did you check that condition, if you can explain? |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 453
Registered: 7-2004
| | Posted on Wednesday, April 06, 2005 - 2:48 pm: |
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I would further investgate the grounding
of the vehicle./ Use good quality coax and
connectors./ 18' of coax is fine./
The Wilson 1000 is close to the performance
of a 102" whip, if you keep having trouble
you may want to consider a smaller antenna
located in a place which would provide a
better ground for you./ Mobile antennas
sometimes drive you nuts...LOL...I know
how you feel./ I just went through the same
trouble with my antenna mounted on my trunk.
I had it in the middle of trunk couldn't
get it down./ I moved antenna 7 inches to
the left and it came down./ I'm still
baffled...LOL...
JIM/ PA/ CEF 375 |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 268
Registered: 2-2005
| | Posted on Wednesday, April 06, 2005 - 5:58 pm: |
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I have reservations about mounting antennas on anything with a hinge. The mount should have a solid ground, and you can't get that through a hinge.
The Wilson 1000 is not close to the performance of a 102" whip. There's nearly twice the metal in the air with a 102" whip. I've run both. There is a big difference. |
Gonemuddin1
New member
Username: Gonemuddin1
Post Number: 2
Registered: 4-2005
| | Posted on Wednesday, April 06, 2005 - 7:09 pm: |
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Racer X, its on the hinge bracket that is mounted directly to the body, not the moving part. The reason it is there now is becuase it was on the hinged part before that wasnt even remotely grounded, and you can imagine what the meter was reading then. Since that problem I checked my ground at that point 10 or more times to make sure it was good. Ill check the ground one more time tho. One other thing i could try is to pull my antenna bracket off the body, clean up the mount and body and put some copper between the two to make sure that the cast iron and steel mount dont rust and I lose the ground.
Thanks for yalls help.
One other question is how can I get the maximum recieve and transmit range from my current setup with out an amp. Thats after I get my SWR sorted out, and I guess with out moving the antenna to the roof Ill be at max performance once I fix the SWR anyway. |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 274
Registered: 2-2005
| | Posted on Wednesday, April 06, 2005 - 8:16 pm: |
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Putting copper between the mount and the body won't accomplish anything. Taking it apart, cleaning it, using some kind of antioxidant compound on the threads will help.
Your best bet for performance would be to mount the antenna directly to the body. A ball mount and spring would work really well as long as it's mounted high on the vehicle. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 354
Registered: 9-2004
| | Posted on Wednesday, April 06, 2005 - 9:12 pm: |
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gonemuddin, the problems you are having are because the antenna is too close to the body of the vehicle, and you're ground connection is not good enough. your meter can only read DC ground. when we are referring to "ground" on an antenna installation, we are referring to RF ground. it is a totally different beast. suffice it to say that if your meter is reading .2 ohms then you've got problems. your meter should read 0.00 ohms. you say that the antenna is mounted on the part of the bracket that is bolted to the body, not the hinged part. that is good, but what is the bracket bolted to? the rear door of your blazer? guess what, another hinge! you need to get that antenna up high on the vehicle so that less than a foot of it is below the roof level. you need to use a ball mount and drill a big hole in the side of your blazer. AND!!! you have to use the spring, it is not just for strain releif. it is part of the antenna. if you are not willing to do these things to your vehicle then please go buy a Wilson 1000 magnet mount and put it on the roof. if you do not mount the 102" whip correctly, it will provide no advantage over using a base loaded whip. this is the age old dilemma; " i want to get out but i dont want to do this or that". SORRY, but that's the trade off. performance comes at a price and there are no shortcuts.
BTW, if you're looking to cut down on corrosion, use the dielectric grease you use on your spark plugs. it works great for this purpose.
hope this helps
matt |
Gonemuddin1
New member
Username: Gonemuddin1
Post Number: 3
Registered: 4-2005
| | Posted on Wednesday, April 06, 2005 - 9:36 pm: |
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Ok thanks for the advise on how to prevent corrosion. The hinge bracket is literally bolted directly to the body, you wont find a better ground, only an equal one. Now I am considering testing the atenna on the upper hinge bracket, that would move it up around 1' and 1". On the spring thing, I dont see how a spring is any better than the piece of brass I machined since in my case the antenna still wants to be longer, and the extension is full 2" taller than a heavy duty spring. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 355
Registered: 9-2004
| | Posted on Wednesday, April 06, 2005 - 10:07 pm: |
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the spring has the correct length of copper braid in the center to provide the correct length. i guess you could experiment with different lengths of brass, but that could bet tedious.i understand not wanting to use the spring because of the bouncing on the freeway, just know that the antenna is designed to be used with the spring and the extra flex of the antenna wont be noticed at the receiving end. if you are worried about the whip hitting the body of the vehicle, i would poke two holes in a tennis ball and slide it down on the whip to just on top of the spring. then only the ball will hit the vehicle.
sounds like you have a good grounding point, but if your meter still says .2 ohms, then it needs some attention. probably just some paint in your way. good luck!
matt |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 455
Registered: 7-2004
| | Posted on Wednesday, April 06, 2005 - 10:27 pm: |
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RACER X,
What i meant was if a 102" whip is on
a vehicles bumper or he couldn't get the
correct ground on the hinge./ A Wilson
1000 placed in the center of the roof
will do just as good./ Both placed on
roof of coarse 102" would be better.
But, who wants a 102" on there roof.
I also have run them both, my Wilson on
the vehicles roof is just as good as a
102" whip on my bumper.
JIM/ PA/ CEF 375 |
Racer_x
Intermediate Member
Username: Racer_x
Post Number: 276
Registered: 2-2005
| | Posted on Thursday, April 07, 2005 - 7:26 am: |
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Gonemuddin1 - The length of the antenna is correct with a spring or your piece of brass. Actually, it would probably be fine with just the antenna itself too. Your match is bad because there is capacitance between the antenna and the body which is detuning the antenna. It's similar to how a gamma match works.
The bad news is that nothing short of mounting the antenna much higher on the body of the vehicle is going to fix it, the good news is that your radio probably doesn't care and will work fine with it that way as long as it hasn't been peaked to death. It won't be ideal, but it'll work.
Why don't you go with a rhino mount? Drill a hole in the middle of the engine hood and mount the whip there. It'll be unique and it'll work a whole lot better. Or get yourself a top loaded fiberglass whip and mount it in the middle of the roof. Don't forget a spring.
Road Warrior - There's the difference. I ran a ball mount, spring, and 102" SS whip mounted right in the middle of the roof of my car. It was MUCH better than the mag mount Wilson 1000 that I was using previously. I experimented with both fiberglass and stainless whips, with and without springs. I settled on the stainless 102" whip on a spring because it was more flexible and less noticeable. |
Hotwire
Intermediate Member
Username: Hotwire
Post Number: 264
Registered: 1-2005
| | Posted on Thursday, April 07, 2005 - 9:29 am: |
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From my expierences, most of the time, but not always!....it is almost impossible to get the swr below 2 with a 102 inch SS whip. In most cases the 6 inch spring is a must and is a very important piece of the setup. The sway back at hi way speeds never made that big of a difference to me. Consider this when mounting and angle the whip just a little bit forward and the whole sway back issue is no more. Like the other members stated, use the shortest widest ground strap and ground the door to the body frame. If you get swr of 2 then be happy and enjoy. |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 458
Registered: 7-2004
| | Posted on Thursday, April 07, 2005 - 10:42 am: |
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Good Luck Gonemuddin1 with your issues.
I wish you the best!
I remember my uncle years ago ran a 102"
with Spring on top his Station Wagon roof.
Hittin those trees limbs & clippin the
ole underpasses...LOL... Thing got knocked
off the car a few times./
JIM/ PA/ CEF 375
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Gonemuddin1
New member
Username: Gonemuddin1
Post Number: 4
Registered: 4-2005
| | Posted on Thursday, April 07, 2005 - 3:25 pm: |
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Allright, thanks for all yalls input. Im going to tinker with it this weekend and see what i can do. Ill try and fill ya in on what i figure out. |
Redwolf_145
New member
Username: Redwolf_145
Post Number: 8
Registered: 4-2005
| | Posted on Friday, April 08, 2005 - 6:10 am: |
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Just Go Get you A mirror Mount and Mount it on the Tire Rack and Put your whip on there and check your SWR... I have Had A Whip on of those vehicle and Worked Great on the tire Rack.... and another person had on as well |
Gonemuddin1
New member
Username: Gonemuddin1
Post Number: 5
Registered: 4-2005
| | Posted on Friday, April 08, 2005 - 11:55 am: |
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Thats strange, Im not sure how it worked great on the tire rack since it isnt even remotely grounded, I know this because thats exactly where I moved the whip from. It recieved decent, but would only tansmit about 2 miles, now that I have moved it to the hinge bracket, I can transmit around 9-10 miles. |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 462
Registered: 7-2004
| | Posted on Friday, April 08, 2005 - 3:18 pm: |
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Since all vehicles are different in some
way or another./ You will have to find
what works best for you on your vehicle./
Thats the fun part...LOL...Good Luck
JIM/ PA/ CEF 375 |
Redwolf_145
Junior Member
Username: Redwolf_145
Post Number: 12
Registered: 4-2005
| | Posted on Friday, April 08, 2005 - 3:53 pm: |
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well you must be doing somethint wrong cause no lie it work perfect.. 2 Diffrent People used it.... one Used the spring and the other didn't us a spring.... |
Brewdirect
Member
Username: Brewdirect
Post Number: 76
Registered: 7-2004
| | Posted on Friday, April 08, 2005 - 5:30 pm: |
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102" whip with a spring should offer a SWR of 1.5 or lower at the least if you have a good ground.
Your coax only needs to be long enough to get from the radio to the antenna.
Your radio shouldn't be a factor in the SWR.
Try removing the L piece if possible and run the coax directly to the antenna.
Try mounting the antenna at a different location to test the ground. Quite possible that something about your mount is not grounding properly.
Check your mount that the antenna screws into. Is the plastic washer seated properly between the two sections?
I ran a 102" whip with spring and had a 1.1 match.
If you have a spare battery cable handy - try attaching it to the mount and run it to the frame. Does your SWR go down? |
Gonemuddin1
New member
Username: Gonemuddin1
Post Number: 6
Registered: 4-2005
| | Posted on Saturday, April 09, 2005 - 10:27 pm: |
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Aight heres the deal, I moved it up a foot to the upper hinge bracket. Tested it and had exactly the same ground. But not that much metal near the antenna. Im now running a spring and the 6" brass. SWR is now at 1.25 chanel 40, and 1.3 channel 1. Im at 13' tall and I believe that is as good as I am going to get. Thanks for everybodys help. |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 372
Registered: 9-2004
| | Posted on Saturday, April 09, 2005 - 11:08 pm: |
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congrats gonemuddin'!
you've done it! that SWR is darn good, and your radio should work well now.
watch the garage!!!
matt |
Redwolf_145
Junior Member
Username: Redwolf_145
Post Number: 16
Registered: 4-2005
| | Posted on Saturday, April 09, 2005 - 11:48 pm: |
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That is What i forgot to tell you that it was on the top bar of the tire rack |
