Grounding hatch mounted antenna

[Intruder]

Ok, so I've got a hatch-mounted ATAS 120 antenna that needs to be well grounded to tune properly. The hatch hinges apparently don't provide enough ground to the body, so I've got some grounding strap, but no idea where to attach it for the best grounding point(s). Any suggestions?

 

[limamike]

Ok, so I've got a hatch-mounted ATAS 120 antenna that needs to be well grounded to tune properly. The hatch hinges apparently don't provide enough ground to the body, so I've got some grounding strap, but no idea where to attach it for the best grounding point(s). Any suggestions?

The ATAS 120 is the antenna, but which mount are you actually using? The Diamond K400?

 

[Intruder]

I'm flipping the coin between the K400 and the Comet RS840. Both seem to be the only heavy duty lip mounts that'll hold the weight of the antenna.

 

[limamike]

I'm flipping the coin between the K400 and the Comet RS840. Both seem to be the only heavy duty lip mounts that'll hold the weight of the antenna.

The K400 grounds itself by cutting through the paint on the mounting screws (on the inside of the hatch), so I doubt you'll need the grounding strap with it. The good thing (and annoying thing) about the K400 is that it loosens up when it hits an obstacle, so it won't break off if you happen to jam your antenna on something like a tree. Simply tighten it back up and you'll be good to go.

 

[Intruder]

My understanding is that the hatch is often not grounded well enough to the chassis through the hinges. The ATAS is supposedly really finicky about tuning properly when it isn't really well grounded from what I've read online.

 

[mace.]

I have the Comet RS840 but haven't installed it yet. I'm guessing it's grounding itself the same way as the k4000. Was planning on giving it a shot tomorrow or Saturday. I'll post with info on how it goes.


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[limamike]

My understanding is that the hatch is often not grounded well enough to the chassis through the hinges. The ATAS is supposedly really finicky about tuning properly when it isn't really well grounded from what I've read online.

I would bet money that you don't need the grounding strap, but the easiest option would be to screw it into the body right on the inside of the hatch opening. I don't think there's an "easy" point of attachment to the frame from that location since you would have to run it through the bottom of the truck and behind some plastic panels. I'm lazy, so I would give it a shot with the K400 alone first and see what you get.

 

[fourwd1]

My understanding is that the hatch is often not grounded well enough to the chassis through the hinges. The ATAS is supposedly really finicky about tuning properly when it isn't really well grounded from what I've read online.

Hatches and hoods typically are not as well grounded as they could be when it comes to RF. I've seen cars where the trunk lid is totally isolated from the rest of the vehicle ground.

Adding a braided ground strap in parallel to each hinge is a start. Of course you have to get down to bare metal at each mounting point or you're wasting your time.
I had an old Jeep Cherokee which had a fiberglass hatch. I created a groundplane on the hatch using aluminum foil tape, then connected that to the rest of the vehicle. Worked decent on 10m.

 

[Ryan1975]

The K400 grounds itself by cutting through the paint on the mounting screws (on the inside of the hatch), so I doubt you'll need the grounding strap with it. The good thing (and annoying thing) about the K400 is that it loosens up when it hits an obstacle, so it won't break off if you happen to jam your antenna on something like a tree. Simply tighten it back up and you'll be good to go.

I've got the K400 on my hatch with the CR8900 antenna.

The only complaint so far is that the hatch is rusting pretty badly now. I may go back to a qtr length antenna on the hood at some point.

 

[Intruder]

I have the Comet RS840 but haven't installed it yet. I'm guessing it's grounding itself the same way as the k4000. Was planning on giving it a shot tomorrow or Saturday. I'll post with info on how it goes.

Cool, let me know.

I would bet money that you don't need the grounding strap, but the easiest option would be to screw it into the body right on the inside of the hatch opening. I don't think there's an "easy" point of attachment to the frame from that location since you would have to run it through the bottom of the truck and behind some plastic panels. I'm lazy, so I would give it a shot with the K400 alone first and see what you get.

Yeah, that was exactly why I posted - no obvious point of attachment to a metal surface on the body around the hatch.

Hatches and hoods typically are not as well grounded as they could be when it comes to RF. I've seen cars where the trunk lid is totally isolated from the rest of the vehicle ground.

Adding a braided ground strap in parallel to each hinge is a start. Of course you have to get down to bare metal at each mounting point or you're wasting your time.
I had an old Jeep Cherokee which had a fiberglass hatch. I created a groundplane on the hatch using aluminum foil tape, then connected that to the rest of the vehicle. Worked decent on 10m.

Yeah, that seems to be the consensus I've found on the HAM forums - the hatch hinges aren't enough of a ground. The problem is that the bolts that attach the hinges to the body are carriage bolts or something similar, so they can't be undone to attach a strap. Wonder if foil tape on the body then attached to the hatch would work.

Getting kind of tempted to ditch the ATAS, give up HF, and instead get a whip style antenna mounted to my ARB. The reason I'm mounting the ATAS on the hatch is that I doubt it would survive contact with branches on the trail.

 

[Intruder]

I've got the K400 on my hatch with the CR8900 antenna.

The only complaint so far is that the hatch is rusting pretty badly now. I may go back to a qtr length antenna on the hood at some point.

Oh wow, that worries me a lot. They use a lot of salt on the roads in the winter up here...

 

[flyrv9]

You could take a meter and measure between the hatch and the rest of the vehicle and see how well the hatch is bonded. Then measure from the vehicle to a known good ground point. A good bond or ground for an antenna is around 2.5 milliohms or .0025 ohms. If you have to install a strap use a braided one and remove the paint from around the hole of the screw or bolt you remove. Or make a new hole. After attaching the strap check the bond again. Once good cover the bare metal with something to prevent corrosion. Clear nail polish will work.

 

[Ryan1975]

Oh wow, that worries me a lot. They use a lot of salt on the roads in the winter up here...

It's not from the screws into the paint...its from the screws that come in contact with the main body as the hatch closes. Those could be ground down and maybe tape on the body so to protect that contact point?

 

[Intruder]

It's not from the screws into the paint...its from the screws that come in contact with the main body as the hatch closes. Those could be ground down and maybe tape on the body so to protect that contact point?

Ah, ok. I'm still thinking that I'm going to ditch the ATAS and hatch mount though. Did a bunch of reading last night (something I should've done before I bought it) and it isn't the greatest. Needs a large ground plane and the HF on it seems mediocre at best. I think for now I'm just going to buy a 1/2 metre antenna that doesn't require much of a ground plane and mount it on my ARB bumper. HF while moving is supposed to be pretty spotty, so eventually I'll just get an HF antenna I can mount on the roof rack when stationary if I want.

I'm not really into it as a hobby, I just got my license for comms when I'm in the truck especially off road, since CB seems to be a dying tech. Up here our distracted driving laws forbid you to use CB while driving, but if you're a licensed amateur you're exempt for some reason.

 

[Okki]

[MENTION=66300]Intruder[/MENTION], What about the roof rack bolts? The bolts for that go straight into the body. It would be an exterior cable, but may be your closest/easiest grounding point near a hatch mounted antenna.

Okki

 

[Intruder]

[MENTION=66300]Intruder[/MENTION], What about the roof rack bolts? The bolts for that go straight into the body. It would be an exterior cable, but may be your closest/easiest grounding point near a hatch mounted antenna.

Okki

Nah, not going to make my truck look ugly just to run this antenna. I bought a Comet SBB5 NMO 1/2 wave antenna this morning that doesn't require much ground and I'm going to mount it on my front bumper. I understand the hobby aspect of amateur radio and don't have anything against it, but for someone like me who only wants to use it as a tool this has been a bit of an ordeal. Hopefully once it's set up I won't have to do anything more than replace a broken antenna every so often.

 

[limamike]

Ah, ok. I'm still thinking that I'm going to ditch the ATAS and hatch mount though. Did a bunch of reading last night (something I should've done before I bought it) and it isn't the greatest. Needs a large ground plane and the HF on it seems mediocre at best. I think for now I'm just going to buy a 1/2 metre antenna that doesn't require much of a ground plane and mount it on my ARB bumper. HF while moving is supposed to be pretty spotty, so eventually I'll just get an HF antenna I can mount on the roof rack when stationary if I want.

I'm not really into it as a hobby, I just got my license for comms when I'm in the truck especially off road, since CB seems to be a dying tech. Up here our distracted driving laws forbid you to use CB while driving, but if you're a licensed amateur you're exempt for some reason.

HF while moving is very spotty. It's been an issue the military has been trying to tackle for a while - hence the high reliance on SATCOM.

 

[Intruder]

HF while moving is very spotty.

Yeah, that's what I've discovered after doing a bunch of reading. The main problem I ran into is the shop where I went was less than honest about that, didn't mention any potential problems with ground planes even though I showed him the truck and mentioned I'd like to attach the antenna somewhere unobtrusive like the rear hatch. I get the feeling he was rather clueless since he didn't mention any possible grounding issues and he also sold me a hatch mount that was not capable of supporting the weight of the antenna. Sorry for the rant, but this has been a little frustrating. Now to run the antenna wire through my firewall (easy) and attach the connector (not a clue).

 

[Okki]

Yeah, that's what I've discovered after doing a bunch of reading. The main problem I ran into is the shop where I went was less than honest about that, didn't mention any potential problems with ground planes even though I showed him the truck and mentioned I'd like to attach the antenna somewhere unobtrusive like the rear hatch. I get the feeling he was rather clueless since he didn't mention any possible grounding issues and he also sold me a hatch mount that was not capable of supporting the weight of the antenna. Sorry for the rant, but this has been a little frustrating. Now to run the antenna wire through my firewall (easy) and attach the connector (not a clue).

I hate BNC connectors. I ended up paying someone to make me a cable. Grounding shorts in the cable are the most common issue. Test your cable before you run it. That should save you some potential headaches.

I ran a small diameter RG316 cable. Those are a bit harder to put connectors on compared to the larger RG8 cable.

Okki