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Dual Coax with single 102"

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I believe the other reason that it needs to be a an odd multiple of a quarter wave per side is that if this is used, both antennas will be forced to have equal currents and in be in phase even if the loads are not perfectly matched in impedance. If this isn't used, the whole idea of using a co-phased system could easily be compromised by having one side slightly different than the other. This method of feeding helps to assure a symmetrical radiation pattern.

lords... Just because it is commonly used, doesn't make it the best way to do things. Aren't you the one that is always harping about doing? You would think with all your sophisticated test equipment (more than all of us combined I think your claim was...) you would know this already and could school me properly.

Mopar
 
right on the mark mopar........

a 1/4 wave line cannot mirror impedance unless extended an additional 1/4 wave.

a 1/2 wave line cannot invert impedance unless extended an additional 1/4 wave.

what i don't understand is how you get to be an engineer without knowing these fundamental basics in addition to the principles of n-slit diffraction and constructive and destructive antenna pattern interference variables along with the mandatory mathematics which are required aptitudes necessary for dealing with phased antenna systems.

oh that's right, i forgot, our centers of higher education have lowered the bar in the last couple of decades, my bad.

thanks mopar.
 
oh that's right, i forgot, our centers of higher education have lowered the bar in the last couple of decades, my bad.

you want to talk about hands on ,yes and over 500 trucks..but in your eyes were all wrong...shame on you book man...you should know better...all units have been running for years without a problem....thank the god you don't install to many and if you do.Pfft

and to top it off also many have been updated with RG8/xx double shield...something out of your erra.....

peace...and thats about the end of this posting...
 
"over 500 trucks..but in your eyes were all wrong."

no, i didn't say that everyone in the forum was wrong, i said that you're wrong. i'm not the ony one here who knows the difference.

i quit counting the trucks and other vehicles after 1972 and you don't know anything about "my era."
 
Palletburner said:
The base station will be in a Double wide mobile home, if that makes any difference.

Would I be better off buying one of those 18'6" base station antennas off of ebay, or somewhere?

Im not too familiar with actual base stations, just mobiles with the power converters in quarry scalehouses, truck shops, gravel pit office, etc., where they only need to reach out about half a mile or so to trucks in the yard. Im using this base station to get out to the pit and shop/office without having to go out to a truck to use the radio. It'll need to reach atleast 3-5 miles, but I'd like to be able to talk to guys a ways away.
Click to expand...

IM not one with a problem with Ebay ,been selling and buying for 6 years now. Yes you can get a Antron 99 for about 50.00, shipping might be around 10 to 15 , but there are other places on the Net you can get them brand new. Just do a Internet search and many retailers will come up for you. You'll need a good line of coax 50 ohm (RG-8x RG-8 RG-213 ect.ect.) Getting some decent hight on your antenna will surely be a plus for your RX and TX , those Antrons will even work in trees if need be without a problem , I think with a fairly decently tuned radio , you will talk much futher then you think with a set up like that.
Also , not sure what your home is made out of ? but I have a friend I've been talking to whom lives in a trailer , he has been using a triple mag-mount with a 102 incher for 15 years (because the trailer court wouldn't let him have a base antenna) he's done very well over the years and has talked 20 miles very well on his set up for what it is. Good luck to you and welcome to the Forum.
 
Thanks for all the replies, I never knew how much math was involved, holy moly.

I havent gotten around to doing the base station yet, but I did buy a single coax and put the 102" on my truck. I could not find any RG-8 but I did find RG-58. Its 18'. I did'nt think the 14' would reach to where I had the mount.

It seems to work well so far, I can hear people clearly now that I used to barely hear, but it doesnt seem to be putting out as good as it used to. I was told it should be grounded, so I ran a ground wire from the mount down to the frame of the truck.

IS there anything else I should do? Its the Uniden PC68XL. The antenna mount is bolted to the side of my aluminum toolbox in the bed, and the end of the coax is the 2 lug connectors.
 
what you can do is run 2 ground straps from frame to the toolbox on each side of the box. leave the ground strap you already have on the mount there. for ground straps you should use flat stranded ground straps (check your local auto parts store), they are better for an rf ground than regular round wire. What I did was got some old thick coax and stripeed the shield out of it and flatened it out. I have a 102" on my toolbox and have a great match. I am feeding it with rg8 18'.

The 102" should be able to tx better than your previous setup, I would try to relocate the whip to the center of your box if you possibly can.
 
Palletburner said:
Thanks for all the replies, I never knew how much math was involved, holy moly.

I havent gotten around to doing the base station yet, but I did buy a single coax and put the 102" on my truck. I could not find any RG-8 but I did find RG-58. Its 18'. I did'nt think the 14' would reach to where I had the mount.

It seems to work well so far, I can hear people clearly now that I used to barely hear, but it doesnt seem to be putting out as good as it used to. I was told it should be grounded, so I ran a ground wire from the mount down to the frame of the truck.

IS there anything else I should do? Its the Uniden PC68XL. The antenna mount is bolted to the side of my aluminum toolbox in the bed, and the end of the coax is the 2 lug connectors.
Click to expand...
No, theres not a whole lot of math involved. You either get an NMO mount with 18' of coax and mount the 102 dead center on your roof. A mobile home has plenty of metal to provide a sufficient ground plane or you get a second 102 and 18' RG-58 dual-phase cable from the local truckstop (and make sure that it is black). You place the two antennas at a minimum of 9' apart and ground the mounts to the mobile home with the shortest ground possible. Check out Wilson's website for details on how to ground. To adjust SWR you don't use the dual-phase, you use an 18' length of single coax and either use an MFJ-269 antenna analyzer or an SWR meter in-line with the antenna that you are going to tune. DON'T try to tune the antennas while they are hooked up to the co-phase cable. You might want to call on a good CB shop to tune them. Unless you live in a valley I don't know why you are going to use a 102, just go with wilson 2K or 5K. If you are dead set on using the 102" and you aren't mobile then put that 102" on a mast and do it right and hook it up with a 7/8" hard-line or Belden 9913 you will have allot less loss in the line.
Also, having two omni-directional antennas will not make both of them directional.
As for putting the 102" on your truck, save the 102" for your base and get a Wilson mag mount for your truck and put it dead center on the roof. The vehicle is your ground plane and you want the antenna in the middle of that ground plane.
 
"No, theres not a whole lot of math involved"
that explains all of the incorrect information and errors. the algebra and simple math alone required to understand the proper phasing and feeding of dual antennas, a pair of 50 ohm loads in parallel connected to a 50 ohm source transmitter would stop this guy dead in his tracks as is evidenced by the following:

"and 18' RG-58 dual-phase cable"
you can't properly phase and feed a pair of 50 ohm antennas with 50 ohm feedline.

"place the two antennas at a minimum of 9' apart"
minimum spacing is 1/8 wavelength.

"DON'T try to tune the antennas while they are hooked up to the co-phase cable"
this is just asinine.

"You might want to call on a good CB shop to tune them"
if this is any example of the the advice you're getting from them then you don't know any good cb shops. try radio shop instead.

"if you are dead set on using the 102" and you aren't mobile then put that 102" on a mast and do it right"

doing it right would entail including some type of elevated radial system up on that pole unless you're good with a 3:1 mismatch.

"hook it up with a 7/8" hard-line
more money than brains.

"having two omni-directional antennas will not make both of them directional"

not the way you're putting them together.

n-slit diffraction in phased antenna arrays

constructive and destructive pattern interference in phased antenna arrays

one day you're trying to change the coil in your 2m antenna because you're worried about a 1.5:1 swr and 10 days later you think you're an antenna expert. only in WWRF. with the exception of your last sentence your last post belongs in the comedy forum.
 
freecell said:
"No, theres not a whole lot of math involved"
that explains all of the incorrect information and errors. the algebra and simple math alone required to understand the proper phasing and feeding of dual antennas, a pair of 50 ohm loads in parallel connected to a 50 ohm source transmitter would stop this guy dead in his tracks as is evidenced by the following:

"and 18' RG-58 dual-phase cable"
you can't properly phase and feed a pair of 50 ohm antennas with 50 ohm feedline.

"place the two antennas at a minimum of 9' apart"
minimum spacing is 1/8 wavelength.

"DON'T try to tune the antennas while they are hooked up to the co-phase cable"
this is just asinine.

"You might want to call on a good CB shop to tune them"
if this is any example of the the advice you're getting from them then you don't know any good cb shops. try radio shop instead.

"if you are dead set on using the 102" and you aren't mobile then put that 102" on a mast and do it right"

doing it right would entail including some type of elevated radial system up on that pole unless you're good with a 3:1 mismatch.

"hook it up with a 7/8" hard-line
more money than brains.

"having two omni-directional antennas will not make both of them directional"

not the way you're putting them together.

n-slit diffraction in phased antenna arrays

constructive and destructive pattern interference in phased antenna arrays

one day you're trying to change the coil in your 2m antenna because you're worried about a 1.5:1 swr and 10 days later you think you're an antenna expert. only in WWRF. with the exception of your last sentence your last post belongs in the comedy forum.
Click to expand...

I love people who try and make everything too difficult and belittle people who simplify things. I follow what I preach and my Wilsons are at 1.1:1.
I wouldn't know how to modify the coils of a wilson 2k to get it to be an 11 meter antenna. Some things I need help on. I am learning lots of things about RF and antenna systems in studying for my upgrades. Everything I have said in my post will get Beetle on a better start than confusing him with math. Antennas can be a bit overwhelming and for someone who may not be on the same level as an MIT professor can get a little confused. If we ask what time it is, we kinda want to know the time, not how a clock works.
 
Freecell, I noticed that you have a link to the CB shop in the Hopi Travel Plaza. Are you affiliated with that shop? If so, I wouldn't let that get out too much aside from the few people that are bedazzled by your "skilz". Most truckers that I know who have had them work on their radios have to take them to GOOD shops like the Indianapolis Pilot shop at exit 4 or the Boise Stage Stop Cb shop and let AL fix them cussing the whole way.
Oh, yeah, and THIS will fit on a truck :LOL:
200px-PAVE_PAWS_Radar_Clear_AFS_Alaska.jpg
 
"I love people who try and make everything too difficult and belittle people who simplify things. I follow what I preach and my Wilsons are at 1.1:1."

well you keep studying and you'll find that vswr is not as important as you have been brainwashed to believe it is. you may see 1:1 but the antenna may actually be RESONANT (and usually is) several ten or even hundreds of khz. away from the freq where you measured that vswr that you're so proud of because what you don't see are values of resistance and reactance. the PATTERN could be as such that most of the radiated signal is wasted up into space instead of down on the ground where you want it. that BALANCED antenna is fed with unbalanced feedline and an unbalanced transmitter which represents more inefficiency and improper feed which also distorts the pattern and the associated symmetry. out of all of them the only thing you may know anything about is the vswr and depending on how it's being measured you may not even know what that actually is. IMPEDANCE is a combination of RESISTANCE and REACTANCE as such that when R = 50 (in a 50 ohm system) and X = 0 the antenna is both matched and resonant at the intended frequency. there are numerous combinations of both R and X that will provide that 1:1 swr but in the sense of the two values that determine the IMPEDANCE the only meaningful swr with respect to the actual operating frequency of the antenna would be the pair of values measured indicating a purely resistive load with no reactance present.

engineers and individuals in the high end of the communications industry install antennas in the ehf band and above where mismatches on the order of 10:1 and higher exist as a matter of course and still attain 85 - 95% efficiency levels when the amount of power generated by the source transmitter is referenced to the amount of power actually radiated by the mismatched antenna. they can do that because they know a lot of something that you don't. you don't see them running around like some stupid cb'er who for the most part believe that if it ain't 1:1 it doesn't work right. in many instances the truth is that a higher swr may represent improved efficiency if ALL parameters are taken into account. wrap your mind around that for a while.

"I am learning lots of things about RF and antenna systems in studying for my upgrades."

yeah, right. you're memorizing the answers to a pool of questions wherein for the most part you have no clue as to why the answers are what they are and couldn't explain why if you had to because those explanations would have to be couched mathematically. ignore the math and physics and learn nothing except how to parrot everything else you've heard.

"Antennas can be a bit overwhelming and for someone who may not be on the same level as an MIT professor can get a little confused."

especially if you're ignoring the mathematics.

"If we ask what time it is, we kinda want to know the time, not how a clock works."

when you ask what time it is i'll give you a simple answer. this is the antenna forum and as such, antenna applications will never be as simple as you seem to think they are and with mathematics and the laws of physics being what they are it never will be.

can't find either of your shops on the internet. here's a google listing of the tech that runs the shop at the plaza.

AB7IF

your boys don't have any creds.

the website sees more traffic than this forum does at over 1,000 hits per hour and finished up the month of march at 747,130 hits, 602,605 files, 196,745 pages, 55,581 visits from 9,549 sites and produced 3,810,648 KB. (3.810 GB.) of host server throughput. comparitively speaking your boys are nobodies.
 
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