Comet RS720 Mounting?

[Krayziekid]

Hey everyone. Quick question for ya. I am mounting my CB antenna (3' Firestik) with the Comet RS720 mount. Want to put it on the driver's side of the rear hatch. I don't want it sticking too far above the roof line, and it seems right by the taillight will be perfect. I did a test fit without fully clamping it, and it seems like it puts a bit of pressure on the taillight housing. More than I think it should. Should I be concerned by this? Should I mount it higher and then just unscrew the antenna when I don't need it? Would love to hear from you guys who have it mounted by the taillight. Thanks everyone!

 

[gm350reratliff]

I use a Comet mount on my 4th gen just like your planning on using. Originally, I purchased the RS720 but it wasn't going to work with the Firestik stud I wanted to use because the hole in the mount was too large. I now run a Comet HD-5, which is kind of similar to the 720. There is also a tab that would contact the tail light but I simply bent it out a bit so it barely touches the tail light. You can see a little more of it in my 4th gen build thread.

 

[Drunner97]

I use a Comet mount on my 4th gen just like your planning on using. Originally, I purchased the RS720 but it wasn't going to work with the Firestik stud I wanted to use because the hole in the mount was too large. I now run a Comet HD-5, which is kind of similar to the 720. There is also a tab that would contact the tail light but I simply bent it out a bit so it barely touches the tail light. You can see a little more of it in my 4th gen build thread.

How did you get your mount to ground on the hatch? I have the RS720, but I couldn't get it grounded well enough to get my 4' Firestik to tune. Threw a mag mount on the roof and had it tuned in no time without a problem so I know it's not an electrical ground or a CB issue.

 

[Krayziekid]

I use a Comet mount on my 4th gen just like your planning on using. Originally, I purchased the RS720 but it wasn't going to work with the Firestik stud I wanted to use because the hole in the mount was too large. I now run a Comet HD-5, which is kind of similar to the 720. There is also a tab that would contact the tail light but I simply bent it out a bit so it barely touches the tail light. You can see a little more of it in my 4th gen build thread.

Yea I figured it out. Turns out the mount fits way better when actually tightened down all the way. Really liking it so far. But as the other guy said, are there grounding issues? I am gonna tune it tomorrow hopefully, but if there are issues, is there a good place to ground it? Thanks!

 

[Drunner97]

Yea I figured it out. Turns out the mount fits way better when actually tightened down all the way. Really liking it so far. But as the other guy said, are there grounding issues? I am gonna tune it tomorrow hopefully, but if there are issues, is there a good place to ground it? Thanks!

I couldn't tune at all. My SWR stayed the same across all channels regardless of changes made to the tuning screw. I also tried removing my spring (to reduce length), as well as a shorter antenna. I sanded down under the lip where the small screws dig into the hatch, I sanded down the bottom of the mount where the Firestik Mount connects to the RS720 (bottom for ground, top for plastic washer to remove ground from actual antenna) Everything short of going to a CB shop.

 

[Krayziekid]

I couldn't tune at all. My SWR stayed the same across all channels regardless of changes made to the tuning screw. I also tried removing my spring (to reduce length), as well as a shorter antenna. I sanded down under the lip where the small screws dig into the hatch, I sanded down the bottom of the mount where the Firestik Mount connects to the RS720 (bottom for ground, top for plastic washer to remove ground from actual antenna) Everything short of going to a CB shop.

Ok thanks. Even if you can't tune it very well, can you still use it? Such as within 30-40 feet of someone? I sort of need it this weekend and don't know if I even have time to tune. Is there a way to ground the mount separately?

 

[gm350reratliff]

How did you get your mount to ground on the hatch? I have the RS720, but I couldn't get it grounded well enough to get my 4' Firestik to tune. Threw a mag mount on the roof and had it tuned in no time without a problem so I know it's not an electrical ground or a CB issue.

To get it to ground, I scraped the paint completely off where I mounted it. After scraping the paint off, I lightly covered that area in some thick dielectric grease, then installed the mount. The mount I ended up using (HD-5) is slightly different than the 720 because the HD-5 has a factory installed stud and ring terminal.

To be honest, I haven't tuned it yet but it seems to work great. I literally installed it just a couple days before the FJsummit and didn't have time to tune. Some day I am going to tune it but the closest cb shop is 100 miles away.

FWIW, I also use a 4' Firestik, HD spring, and quick disconnect.

What stud are you using with the 720?

Yea I figured it out. Turns out the mount fits way better when actually tightened down all the way. Really liking it so far. But as the other guy said, are there grounding issues? I am gonna tune it tomorrow hopefully, but if there are issues, is there a good place to ground it? Thanks!

If you absolutely can't get it to ground to the hatch, you may have to run a dedicated ground strap to the body. What stud are you using? It was my understanding that the 720 has a larger hole for a PL259 style mount which is not coax cable. That is where you may have issues grounding.

 

[Krayziekid]

To get it to ground, I scraped the paint completely off where I mounted it. After scraping the paint off, I lightly covered that area in some thick dielectric grease, then installed the mount. The mount I ended up using (HD-5) is slightly different than the 720 because the HD-5 has a factory installed stud and ring terminal.

To be honest, I haven't tuned it yet but it seems to work great. I literally installed it just a couple days before the FJsummit and didn't have time to tune. Some day I am going to tune it but the closest cb shop is 100 miles away.

FWIW, I also use a 4' Firestik, HD spring, and quick disconnect.

What stud are you using with the 720?



If you absolutely can't get it to ground to the hatch, you may have to run a dedicated ground strap to the body. What stud are you using? It was my understanding that the 720 has a larger hole for a PL259 style mount which is not coax cable. That is where you may have issues grounding.

I ended up using a fire ring coax with the firestik stud and a 3' antenna w/spring. I haven't finished wiring my CB yet, so I can't tell you I've tried it. But have everything mounted and ready to go. as long as it works in short range/LOS, I will be happy. From what I can tell though, the fire ring fits the hole perfectly. I could be wrong though cause I don't know a ton about this.

 

[Drunner97]

To get it to ground, I scraped the paint completely off where I mounted it. After scraping the paint off, I lightly covered that area in some thick dielectric grease, then installed the mount. The mount I ended up using (HD-5) is slightly different than the 720 because the HD-5 has a factory installed stud and ring terminal.

To be honest, I haven't tuned it yet but it seems to work great. I literally installed it just a couple days before the FJsummit and didn't have time to tune. Some day I am going to tune it but the closest cb shop is 100 miles away.

FWIW, I also use a 4' Firestik, HD spring, and quick disconnect.

What stud are you using with the 720?

If you absolutely can't get it to ground to the hatch, you may have to run a dedicated ground strap to the body. What stud are you using? It was my understanding that the 720 has a larger hole for a PL259 style mount which is not coax cable. That is where you may have issues grounding.

There's two 720 mounts. One is a NMO which is 5/8s, and the other is just regular which 3/4. I used the 3/4 720 with the Firestik Stud Mount.

http://www.amazon.com/gp/product/B00T4RSQ92?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

Maybe I just wasn't getting a good enough connection with the stud mount to the 720.

Ok thanks. Even if you can't tune it very well, can you still use it? Such as within 30-40 feet of someone? I sort of need it this weekend and don't know if I even have time to tune. Is there a way to ground the mount separately?

I could receive, and I even risked the high SWR transmit a couple times, but I never got a response. So I'd say you can at least listen if you can't get it tuned.

At this point I'm on the fence whether I'm going to keep the 720 mount, or make an adapter to fit between the bumper and the tail light. The Lil Wil mag mount works great, but I don't like that it's pretty static. I wanted the flexibility of removing the antenna when I wanted and aesthetically I prefer the look of the 4' Firestik over the Lil Wil. Unfortunately I really haven't found a whole lot of info on too many people successfully using the 720 so if you can get it to work you should post the cable/radio/setup you used.

 

[Krayziekid]

There's two 720 mounts. One is a NMO which is 5/8s, and the other is just regular which 3/4. I used the 3/4 720 with the Firestik Stud Mount.

Amazon.com: FIRESTIK K-4A CB RADIO ANTENNA HEAVY DUTY SO-239 STUD MOUNT (BULK): Sports & Outdoors

Maybe I just wasn't getting a good enough connection with the stud mount to the 720.



I could receive, and I even risked the high SWR transmit a couple times, but I never got a response. So I'd say you can at least listen if you can't get it tuned.

At this point I'm on the fence whether I'm going to keep the 720 mount, or make an adapter to fit between the bumper and the tail light. The Lil Wil mag mount works great, but I don't like that it's pretty static. I wanted the flexibility of removing the antenna when I wanted and aesthetically I prefer the look of the 4' Firestik over the Lil Wil. Unfortunately I really haven't found a whole lot of info on too many people successfully using the 720 so if you can get it to work you should post the cable/radio/setup you used.

Is it dangerous to transmit with a high SWR/un-tuned antenna?

 

[Drunner97]

Is it dangerous to transmit with a high SWR/un-tuned antenna?

You could fry your radio if it's 3+

 

[gm350reratliff]

There's two 720 mounts. One is a NMO which is 5/8s, and the other is just regular which 3/4. I used the 3/4 720 with the Firestik Stud Mount.

Amazon.com: FIRESTIK K-4A CB RADIO ANTENNA HEAVY DUTY SO-239 STUD MOUNT (BULK): Sports & Outdoors

Gotcha. I might've had the wrong mount/Firestik stud then. I've never really had a cb radio in my own vehicle before even though I installed quite a few over the years for other people. They just always seemed to work without tuning.


Maybe I just wasn't getting a good enough connection with the stud mount to the 720.



I could receive, and I even risked the high SWR transmit a couple times, but I never got a response. So I'd say you can at least listen if you can't get it tuned.

At this point I'm on the fence whether I'm going to keep the 720 mount, or make an adapter to fit between the bumper and the tail light. The Lil Wil mag mount works great, but I don't like that it's pretty static. I wanted the flexibility of removing the antenna when I wanted and aesthetically I prefer the look of the 4' Firestik over the Lil Wil. Unfortunately I really haven't found a whole lot of info on too many people successfully using the 720 so if you can get it to work you should post the cable/radio/setup you used.

To be honest, I'm not 100% happy with the comet mount either. The mount flexes a little more than I'd prefer and there was a large cast washer which holds the two halves together that broke on Imogene pass in CO. Fortunately, I had some spare washers in my tool bag that day. Actually, the washers are still on there because they seem to do a better job at holding it together. My plan is to build a nice rear bumper and move the antenna to that.

Is it dangerous to transmit with a high SWR/un-tuned antenna?

Only to the radio. You could fry the radio trying to transmit with high SWR.

 

[Drunner97]

My plan is to win the lottery and get a CBI rear with swing out, tire holder, and can holders. Then mount the Firestik to that. =P


I'm awhile out from that though, maybe for my birthday in February depending on how tax season goes.