Coax facts

Mike what is that #

 

You use a short jumper to connect an antenna analyzer to the PL259 on the underside of the antenna mount.

 

???.....Are you talking about length of the coax? If so, it depends. If everything is right it won't matter. If you have rf ground problems, you'll just have to play with the length. 9ft is plenty long for the trucks I drive, but I can't get a SWR reading below 2:1 unless I use 18ft of coax. I slip seat so I have to compromise. If I drove the same truck every week, I'd fix the rf ground problem.....or at least try. Since I don't, I compensate with coax length so I don't damage my finals.

 

the coax length is based on a three inch increment. How ever most have a hard time getting the precise, at that length there is no forgiveness. Its comonly measured in three foot increments because there is a wider range of forgiveness. The swr,'s can be tuned with a tuneable antenna. Use a 3 foot jumper to connect radio transmitter to anything aad use the three foot measurment for your coax to your antenna and you will be fine. Just don't coil up your wire for it can cause a magnatism and make swr's high. Good luck.

 

We should first remember that if the coax length is having more than a very minor affect on the SWR's then there are other problems that need to be addressed with the antenna or "mounting of the antenna" or "where it is mounted " that sort of thing. Sometimes you can do things to help or correct that antenna mounting but if you cant and the coax becomes essentially another element of the antenna then you will have to use the coax length to establish a load or "SWR" that the radio can live with.. This will be fine to do just remember nothing you do with the coax will change the antennas performance in the sense that it would change or make it work better.. What I guess I should say is that if the antenna was really a 3.1 to 1 match and you managed to make the radio belive it was 1.4 to 1 by making the coax a certain length then the antenna would still be 3.1 to 1 it would only allow the radio to see a match that it could live with and the performance of the antenna would not be changed ... And sometimes that may be what you must live with....I have found a way that you can establish a good ground on Trucks when all else seems to fail. Take a mount just like the mount you use for the antenna and mount it upside down just beside the vertical antenna take the slug the antenna screws into and remove the nylon insulator and screw the slug back on the mount this will allow the antenna you screw into this mount point down and be grounded and allow you form a dipole. Every time I have ever tried this on a truck it has worked beautifully. Just something to think about in the event you can't seem to establish a good RF ground. Yes it may not be something you want to see on your truck but it does work and it certainly will get some attention like what kind a F@@king antenna is that but aside from all that they work really well when done right..

 

Yeah, well, I've done this and it doesn't always work either......just sayin! (worth a try though)

 

First there is nothing about 3 inch increments that would mean much at 27Mhz it could at 800 Mhz but if 3 inch increments is having an affect with a CB antenna you have some real serious problems...

The truth about coax length specifically the 18Ft length is simple.. I worked for Hustler antenna back in the late 70's and early 80's as a team who's job was to come up the ultimate coax length not just for performance issues but also for manufacturing issues and making the antennas as useable to the DIY'ers in CB as to make it the best possible scenario for more or less plug'n Play antennas.. It didn't take long for Hustler and other companies to figure out that if a good match on the SWR meter was going to be achieved by almost everyone that it would be with 18Ft of coax.. We also knew that it didn't always translate to the best design but it certainly made experts out of almost eveyone that installed there own antennas which was the goal.. You could actually get good results with very short antennas with 18ft of coax just remember that does not mean the best performance it only means it made meter readers happy to see a useable match without much technical ability needed.. The beauty of this 18Ft was simple if you keep in mind that the length really doesn't mean anything if the antenna is designed and installed in a way that meets all the criteria for a proper and efficient system the coax can be 6 inches or 5ft 2inches of anything you want. So with all that in mind it goes back to the same thing I have been preaching for ever you can get a perfect match on a 10 inch antenna but you wont talk more than a mile maybe if you are lucky so SWR's are nothing more than something you need to make the radio happy it doesn't mean the antenna you have will talk 15 miles like the 9Ft stainless steel whip will and that whip will do that with a 2 to 1 SWR. At Hustler we focused on one thing making all our antennas as efficient as possible, But also making them as user friendly as possible we installed out antennas on every kind of vehicle you can imagine we actually used the cars of employees to test them on in return for letting them keep the antennas after all it was PR and advertising to have all the employees with Hustler antennas and or Antler which was also owned by Hustler till they dropped the product line about 25 years ago..

Another way of describing this ::

feedline/Coax length could affect the antenna's behavior: when 1) the shield of the coax acts like part of the antenna and radiates/receives. That's not supposed to happen, because no two stations will run their feedlines exactly the same way and it would add a random element to the performance of the antenna. Also, in the case of transceivers, it brings RF back to the radio and operator which can mess with nearby electronics (at higher power levels it can even cause burns). Well designed and built antennas should keep that from happening. Halfassed designs, which are quite common in the CB market, might find that they can minimize the effects of RF on the shield by making the coax certain fractions of the free-space wavelength.

 

Fixed for you...

 

Anyone know what happened to the signalengineering.com pages. Particularly the coax basics and ultimate 11 meter antenna guides?