How to repair coax cable
04-29-2015, 09:11 AM
#11
This is your problem. You can't cut the coax down like that. It is at a specific length for a reason. The kink at the end probably isn't helping either. I would just replace it.
05-02-2015, 03:58 PM
#12
JK Enthusiast
After a bit of homework on Firestick antennas, I have come to the following conclusion.
Correct, the kink in the cable is not good, however, actually you can cut the coax. Firestick makes two types of antennas, Ground plane dependent and No Ground Plane (NGP). The ground plane dependent antennas are the KW and FS models, the NGP antennas are the FG and LG.
Ground plane dependent antennas use the car body as the counterpoise for the antenna. In this configuration it is very important to be sure that the antenna mounting stud is well connected, electrically, to the body panel that it is being mounted onto and then the body panel has a good ground strap or electrical connection to the rest of the car. In this setup, the length of the cable is not important since it is merely a transmission line for the RF signal between the radio and the antenna. In fact, if you find that the cable length does have an effect on the antenna performance, then there is most likely a problem elsewhere in your setup. Either the radio is not grounded properly, the body panels are not well grounded, or maybe the antenna is mounted too low on the body and there is reflection between the antenna and a body panel.
No Ground Plane antennas use the coax cable as the counterpoise for the antenna. They are dependent on the length of the antenna cable. NGP antennas are normally used on vehicles that are not metal. Fiberglass cars and boats for example. Since there is no metal surface to act as the ground plane for the antenna the outside shielding of the cable acts as the ground plane. You should not use a standard type mount with an NGP antenna as a standard mount connects the outer shield of the cable to the body where an NGP mount does not. NGP antennas are typically about 20% less efficient than a 1/4 wavelength whip. In this configuration the length of the cable is very important. Shortening the cable changes the electrical characteristic of the antenna and may make it impossible to tune for a given frequency.
Now, from the photo it looks like the mount being used is the K-4 mount. This mount uses the car body as the ground plane so it is not an NGP antenna, and therefore is not dependent on cable length.
Lastly, I believe that you could replace the cable with a piece of standard coax and instead of the Firering connector, use two ring terminals with a nylon washer between them.
Good Luck
Correct, the kink in the cable is not good, however, actually you can cut the coax. Firestick makes two types of antennas, Ground plane dependent and No Ground Plane (NGP). The ground plane dependent antennas are the KW and FS models, the NGP antennas are the FG and LG.
Ground plane dependent antennas use the car body as the counterpoise for the antenna. In this configuration it is very important to be sure that the antenna mounting stud is well connected, electrically, to the body panel that it is being mounted onto and then the body panel has a good ground strap or electrical connection to the rest of the car. In this setup, the length of the cable is not important since it is merely a transmission line for the RF signal between the radio and the antenna. In fact, if you find that the cable length does have an effect on the antenna performance, then there is most likely a problem elsewhere in your setup. Either the radio is not grounded properly, the body panels are not well grounded, or maybe the antenna is mounted too low on the body and there is reflection between the antenna and a body panel.
No Ground Plane antennas use the coax cable as the counterpoise for the antenna. They are dependent on the length of the antenna cable. NGP antennas are normally used on vehicles that are not metal. Fiberglass cars and boats for example. Since there is no metal surface to act as the ground plane for the antenna the outside shielding of the cable acts as the ground plane. You should not use a standard type mount with an NGP antenna as a standard mount connects the outer shield of the cable to the body where an NGP mount does not. NGP antennas are typically about 20% less efficient than a 1/4 wavelength whip. In this configuration the length of the cable is very important. Shortening the cable changes the electrical characteristic of the antenna and may make it impossible to tune for a given frequency.
Now, from the photo it looks like the mount being used is the K-4 mount. This mount uses the car body as the ground plane so it is not an NGP antenna, and therefore is not dependent on cable length.
Lastly, I believe that you could replace the cable with a piece of standard coax and instead of the Firering connector, use two ring terminals with a nylon washer between them.
Good Luck
Last edited by maxspongebob; 05-02-2015 at 04:00 PM.
05-03-2015, 11:26 AM
#13
JK Enthusiast
It is a shame that Firestik promotes coax length as a means to sell "no ground plane" antennas. It is a myth (and a long technical discussion beyond that). Fact is, the best antenna for a mobile installation to compensate for a poor ground plane is a half-wave antenna, which is not perfect but due to the electrical characteristics they out perform the 1/4 and 5/8 antennas.