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Coax For Cophase Setup
- Thread starter DJboutit
- Start date
On a cophase setup, I believe you are supposed to use 75 ohm coax. Like RG 59 - not RG 58.
That is supposed to be used between the 'tee' and the antennas. If I'm also mistaken, then the length of the coax from the 'tee' to the radio must be 18 ft. The distance between the two antennas is supposed to be a 1/4 wavelength between each other - or appoximately 9 ft.
But I really can't say. That setup is usually used for diesel rigs. Most passenger cars/trucks can't use it because they don't have the dimensional width requirement of 9 ft apart. I never had to set one up. What were you going to put it on?
That is supposed to be used between the 'tee' and the antennas. If I'm also mistaken, then the length of the coax from the 'tee' to the radio must be 18 ft. The distance between the two antennas is supposed to be a 1/4 wavelength between each other - or appoximately 9 ft.
But I really can't say. That setup is usually used for diesel rigs. Most passenger cars/trucks can't use it because they don't have the dimensional width requirement of 9 ft apart. I never had to set one up. What were you going to put it on?
Rob is on the right track. You need 75 ohm coax for the phasing harness. The length depends on what you are trying to accomplish. A typical trucker setup that is installed so the antennas are on either side of the cab is usually trying to accomplish an elliptical signal pattern: one that is stronger to the front and rear but still has some signal to the sides. To do that, you need to feed each antenna with a length of coax that is an odd quarter wave multiple: 1/4 wave, 3/4 wave, 5/4 wave, or something similar. For the typical mobile/truck install, that's going to be either 6 feet (1/4 wave) or 18 feet (3/4 wave) depending on the length. You can run both cables directly into the PL-259 and connect that to your radio.
Keep in mind that you can sort of direct the signal the way you want to with a cophase setup if you have the antennas spaced properly. Let us know what you're trying to accomplish and we can give you more precise advice.
Keep in mind that you can sort of direct the signal the way you want to with a cophase setup if you have the antennas spaced properly. Let us know what you're trying to accomplish and we can give you more precise advice.
I plan to run 2 mr coily enforcer comps on the sides of my mini van like the way truck drivers setup there antennas. If put them on the roof the antennas would be to tall to drive around, on the side I can run them they well be 67" to 69" apart have one setup already still need to get one more.
The placement of the antennas does not determine the type of coax you'll need, like the 2 previous posters stated you'll have to make a 50 ohm pigtale and then t-off that with 75 ohm coax to the antennas and you'll not like the results that you're gonna have mounting those antennas that close to each other.
They need to be 108'' apart to react as they're suppose too.
The distance between those two antennas will determine how directional the are. Larger separations make for more directionality than less separation. Something on the order of about 1/4 wave length separation is thought of as the minimum distance for practical use. shorter separation distances are certainly possible, just not very usable for a directional antenna system (the only thing those dual antennas are good for).
Would they work if you only have something like 60 - 65 inches separation? Yes, but not as well as if they were further apart. Would it be worth doing? I can only speak for myself, and since I don't see any practical use for dual antennas at all, I'm not too sure you want my answer to that. You decide for yourself.
- 'Doc
Oh, running the power you are talking about is just going to make it even more 'fun'! Lots of voltage involved with the type of impedance matching you're talking about doing, start looking for some RG-9, at least, doubt if RG-59 will work very well. Have fun.
Would they work if you only have something like 60 - 65 inches separation? Yes, but not as well as if they were further apart. Would it be worth doing? I can only speak for myself, and since I don't see any practical use for dual antennas at all, I'm not too sure you want my answer to that. You decide for yourself.
- 'Doc
Oh, running the power you are talking about is just going to make it even more 'fun'! Lots of voltage involved with the type of impedance matching you're talking about doing, start looking for some RG-9, at least, doubt if RG-59 will work very well. Have fun.
ButtFuzz
Anti-BS Advocate ● WO0WOO ● Reverend Doctor
Go to truckstop, or CB shop near thereto.
examine co-phase harnesses.
purchase one that looks of quality build.
Hook it up.
examine co-phase harnesses.
purchase one that looks of quality build.
Hook it up.
A lot of the clear mini-8 that I've seen for sale at truck stops is marketed by Wilson. It's good quality RG8x, 50 ohm coax, if it is. Most truck stops also have cophase harness, which is 18' of 75 ohm coax, but it it two cables with a common, single PL-249 connector on one end. That's the one you want...not the clear mini-8.
Sure - just don't expect to run a lot of power thru it. Even cheap coax can handle ~300 watts minimum. Only the better coax has the better/higher power rating. Two antennas cophased needs to have RG-9 or 59. The 9 will handle more.
What kind of vehicle were you going to put it on?
