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Chris
| | Posted on Friday, October 25, 2002 - 5:42 am: | 
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Several questions in here, just trying to find the right combo and what works good.
Well, I have been playing around in placement,and mounts of my antenna. I still have the antenna that came with the radio, but I'm not sure what it is. When I chatted with you last I was running with it on the roof, mag mount. (I have a 92 F-350 Crew Cab.) i wanted to try a differnt mount trying to get a good ground. I have made a bracket and attached it to the bed rail behind the cab and from there i have attached another antenna,not sure what it is either. Overall I'm the same height as before but the signal on receive is better and forward modulation i pegged the meter, but when i checked my swr's I was way off( 3 to 1)and wouldnt get better. With my mag mount my swr's are great. Im running 1.3 to 1 on channels 1 and 40. I thought that i would get a better ground going right to the metal of the truck? I would like to keep the mount on the bed rail and get a 102" whip now. How is there a differences in ground planes between mounting on the roof and behind the cab? And should I get a 102" whip or stick with a mag mount W 1000 or 5000?
Thanks for your help and sorry its so long....
Chris in AZ |
Chris
| | Posted on Friday, October 25, 2002 - 7:41 am: |
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I was justing reading about a comparsion between the 102" and the firestik kw7. which one of these would you chose? just curious.. And I also found where it is not recommened to mount your antenna close to any vertical plane, saying this would cause unacceptable SWR. Is that what happened to me when I moved the antenna behind the cab? and if so what could I do to better the swr without going back to a mag mount.
I'm only asking these dumb questions to figure out what to buy and what I need. I like the mount behind the cab that way i can use a longer antenna, but if my rig works better on top i may have to stick with a roof mount.... Thanks in advance for any response...
Chris in AZ |
bruce
| | Posted on Friday, October 25, 2002 - 7:46 am: |
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I like the 102 wip but if you want to see if your antenna just needs to be tweeked try the following... chris ive seen this if your antenna was on a mag mount and you move it to a grounded mount sometimes you need to change the length now here how to check to see where it is tuned if all you have is a 40 ch it may be a problem but check at ch 1 ch 20 ch 40 VERY carefully set the meter full scale and go to swr write down carefully the exact reading ...... just to use ramdom numbers lets say its 2.8/1 on ch 1, 3.0/1 on ch 20, 3.2/1 on ch 40 the wip is too long ..... if 3.2/1 on ch 1 and 2.8 on ch 40 its too short. NOW say it looks to short add a piece of wirt to the top of the wip say 3 inches get a good electral conection and tack it in place with a strip of tape measure again if the swr went up chances are the wip was too long to begin with but check it anyway if it went DOWN and is under 2/1 get a wip replacement from radio shack thats at least as long as the final cut that you need to make on that tacked on piece to get it down under 1.5/1.
One more trick you know the rool up steel yard sticks they come like 6-25 foot in a steel contaner well unscrew your wip and tape one to the top of the coil and using the lock set it for the same lengh as your wip and tweek it up and down to get about the right lengh using the lock to hold it when your done put the wip with the exstension wire back in cut just a bit longer and see it you found the right length...... you have no idea how many times ive done this i have a 6 foot rool up that is in a steel container ant without cutting wip after wip it will get you close THEN you get and cut a wip!
Arn't antennas fun.....
Bruce |
Dx431
| | Posted on Friday, October 25, 2002 - 12:28 pm: |
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Chris, The high reading you got, were these with the firestick or with the whip? I mounted a 102" whip behind the cab of my truck and have a 1.2 swr on all 40 chnls. Anything short a 102" whip mounted behind the cab will not perform as well and show high swrs. |
Alsworld
| | Posted on Friday, October 25, 2002 - 5:53 pm: |
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I would think this all relates back to exactly what Ironmask was relating in the prior post (the original post prior to this one).
If you have a good ground but high SWR's, the antenna is reflecting back onto itself creating high SWR's instead of properly sending the signal.
Try various spots first. A 102" whip is the most efficient at what you are looking for.
Alsworld |
Chris
| | Posted on Saturday, October 26, 2002 - 3:42 am: |
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Bruce,
Thanks for the helpful info. By what you have told me and retesting my SWR, my antenna is to high, and you were right about taking it off a mag mount.. i'm going to try your technique. It cant hurt plus Im learning as I go.
Thanks again
Chris in AZ |
Chris
| | Posted on Saturday, October 26, 2002 - 3:58 am: |
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Alsworld,
I was looking for the prior post and im not sure were you are talking about. let me know there. I have a good ground. I have went through and checked everything i know to check. I printed a diagram off the net that showed what i should be testing and reading. As far as different locations, I understand that you must have at least 50% above your vehicle? Not sure though. So with the antenna that i have now that limits me. And I would like to keep it some where in the center, there again I heard that is the best place to mount.Due to the ground plane?
Im willing to try anything, so if you have any suggestions to where to mount let me know.
Thanks for the info.
Chris in az |
Chris
| | Posted on Saturday, October 26, 2002 - 4:19 am: |
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I have another ?..
I have been reading about coax cable. I know that im going to get some new stuff, just not sure what to get. I have seen the rg8, rg58, and this 213. Can someone tell me? Is the smaller # a smaller cable, and the bigger the # the bigger the cable? And what size should I go with a 102" whip? And is it better to get a longer cable. Now I have a 9' cable.
Im just full of questions... I can say when I first started in cbing, i thought it was plug it in and go, but im learning that it is nothing like that. Thanks again for all your help
Chris in az |
Alsworld
| | Posted on Saturday, October 26, 2002 - 10:12 am: |
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Chris,
my apologies as I got this post confused and related to another which were from two different authors. I should have looked first. Sorry for sending you on a wild goose chase, it was unintentional I assure you. The post Ironmask replied to (that I referenced as the "original") was about custom Trailer hitch mounts. It was a recent post here on the Open Forum and maybe Ironmask comments might be applicable here as well.
The coax numbers do not relate to size. Here is general sizes:
RG-58 small diameter coax slightly smaller than a pencil
RG-8x, or RG-8U(mini), LMR240: just a tad larger.
RG-8 and RG-213 are both larger, about the size of your pinky finger.
Larger coax handles more power with less loss, but short runs of smaller coax are fine, and perfect for vehicle installations due to size and flexibility.
Bruce tell me if I'm crazy here. Now for the antenna's, plug and play a Wilson 1000 or 5000 magnet mount would do that fine. But, being we are learning, I've got to point this out.
Most off the shelf magnet mount antennas come with 18 ft of coax. I know where base stations we keep the run as short as possible, but I've seen where vehicle mounts, 18 ft is the magic length. Bruce??? I don't want to bring up a "cut coax length to better the swr's" debate but for mobiles, 18ft just sticks in my mind. It's a 1/2 wave length anyway so shoot away Bruce. Could this be a factor here with Chris only running 9ft at the present? It seems he should be able to make a 102" work without cutting it.
Alsworld |
Dx431
| | Posted on Saturday, October 26, 2002 - 11:33 am: |
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Alsworld, I find that the 102" whip works with just about any length coax. I have mini 8 on mine and it is about 17' ( from having to to reinstall connectors ) and it works just fine. I have run 9' with the same set up as I have now with the same swrs ( 1.2 ) and with good reports. As soon as figure how to post my pix I will post them in the "Pics of Mobile Set Up" section. |
Chris
| | Posted on Saturday, October 26, 2002 - 3:20 pm: |
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Dx431,
I thought i posted a response to you but i guess it didnt go through. I dont have a idea what my antennas are now. I purchased them at a swap meet and neither of them have any kind of writing on them. But im leaning more to getting a 102" whip. Just got a couple of ?'s for you. You said that you mounted your 102 right behind the cab.... What kind of mount? And do you have it on a 5" spring? How far away from the cab is your antenna, did you have to put something on it to prevent it from banging on your cab? I would like to see your pics, so i could get an idea. My email is: 4ofusinaz@msn.com...
And as far as getting new coax, what would you perfer? im going to get new cable anyway cause what im running I have no idea how old it is.. So should I get 18' or stick with 9'?
Thanks for your help and Im glad to hear your rig works, that encourages me that I moving in the right direction. Hope I can see your pics....
Thanks
Chris in Az |
rharper
| | Posted on Thursday, January 02, 2003 - 10:36 am: |
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Another good feature about the 102" whip is it's broad-banded abilities. With my EURO 3900, I can cover 25.6-28.5 mhz with an acceptable(2-1 or less) SWR. Not many other mobile whips will do that right out of the package. The only thing I did to help this antenna was to hook a large wire from the mount to the frame of my F-150. Since I got a good match (1-1 on Ch.20) and the entire range of the radio within the 2-1 range, can't imagine why I would want to use anything else - except when I go through the McDonald's Drive-Thru (grin). |
bruce
| | Posted on Thursday, January 02, 2003 - 12:43 pm: |
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rharper my 102 is realy 97 since its tunned to 28.8 but in a pinch it will go down to 28 and up to 29.7 at 1.7/1 not bad! |
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