How to create a ground plane

[Mogman]

So I am installing the helmet top on my HMMWV and am contemplating ways to create as much of a ground plane as possible.
I plan on running a vast amount of radio equipment including a 500W HF station and would like to avoid over exposure and make antenna matching as easy as possible.
Thin sheet aluminum comes to mind, copper would be easier to bond (electrically).
A spray in option would be great if it exists.

 

[antennaclimber]

Are you mounting all of the antennas on the roof?

 

[Mogman]

Are you mounting all of the antennas on the roof?

No but most will have the radiating elements above the roof, the big HF antenna will be on an offset mount and likely with a base extension to get the base to roof level

 

[antennaclimber]

If you can mount antennas on the roof, put as large a piece of aluminum under the antennas as possible. The roof location maximizes the performance of antennas. The ground of the antenna needs to be mechanically connected to the aluminum. To increase the metal area, add as much aluminum tape as possible to the interior of the roof area. The aluminum tape needs to be electrically connected to the large metal plate. If you are planning on installing more than one antenna on the roof, try to keep the antennas as far a part as possible, yet keep them at least 1/4 wavelength from the edge of the metal plate. Try not to install them closer than 1/4 wave length of the lowest frequency. Best to use a NMO thick roof mount kit for VHF or UHF antennas. Thickness of the aluminum does not make a difference electrically.

As for the HF antenna, again the higher the better. If you can get the base of the antenna above the roof line, it will work better. Ensure that the metal base mount is electrically and mechanically connected to the metal frame of the vehicle. This can be accomplished with a good quality metal braid.
Try to keep the metal braid as short and as direct as possible to the frame ground. Clean all connections prior to installation.

Antennas that are mounted on the sides, corners, hood, trunk deck and other places not on the roof, will have directional patterns. Roof mounted antennas will offer a more uniform omnidirectional pattern.

Attached are pictures of how I did my M1009 and M1008 HF, VHF and UHF antennas.

I hope this helps.

 

[Mogman]

If you can mount antennas on the roof, put as large a piece of aluminum under the antennas as possible. The roof location maximizes the performance of antennas. The ground of the antenna needs to be mechanically connected to the aluminum. To increase the metal area, add as much aluminum tape as possible to the interior of the roof area. The aluminum tape needs to be electrically connected to the large metal plate. If you are planning on installing more than one antenna on the roof, try to keep the antennas as far a part as possible, yet keep them at least 1/4 wavelength from the edge of the metal plate. Try not to install them closer than 1/4 wave length of the lowest frequency. Best to use a NMO thick roof mount kit for VHF or UHF antennas. Thickness of the aluminum does not make a difference electrically.

As for the HF antenna, again the higher the better. If you can get the base of the antenna above the roof line, it will work better. Ensure that the metal base mount is electrically and mechanically connected to the metal frame of the vehicle. This can be accomplished with a good quality metal braid.
Try to keep the metal braid as short and as direct as possible to the frame ground. Clean all connections prior to installation.

Antennas that are mounted on the sides, corners, hood, trunk deck and other places not on the roof, will have directional patterns. Roof mounted antennas will offer a more uniform omnidirectional pattern.

Attached are pictures of how I did my M1009 and M1008 HF, VHF and UHF antennas.

I hope this helps.

Thanks, I am well aware of sound RF practices, I was a communications/SCADA tech for 37 years.

 

[MarkM]

What bands will you be using and will this setup be used stationary or mobile or both.?

Mark

 

[Mogman]

For HF/VHF/UHF (mostly for HF/UHF) I will be using a IC706MKIIG, ALS500RM amp and a SCG235 tuner into a Harris SB-V16/V35 HF Whip Mobile and whatever my imagination can come up with stationary.
#2 VHF rig will be a Racal VRM5080 and its matching auto tuner and whip.
#3 VHF will be a 110W Motorola XTL5000, allot of P25 traffic around here.
A receive only Icom IC-R2500 which covers DC to Daylight also with P25 capabilities and dual receivers.
And of course a laptop with Starlink for internet connectivity, connected to the PCR to hunt down on air signals and make changes to the XTL programming
All of these radios have remote head capabilities, plans are to install an overhead console like they used to put in the hippy vans and most of the radios in the side boxes/ under seats

 

[Mogman]

The only component I do not have besides the Starlink (waiting for new version) is the ALS500, I keep hoping something more reliable will come along.
Maybe something 24V, there are allot of 48V amps/components etc. out there.
I have a few Harris RF110A's that are totally bullet proof but that would require a 5KW gen and trailer, still might be something for field day, dang things will run 1KW RTTY into a 4.5:1 load 24-7 they just loaf along at legal and easily top 2KW PEP into a dummy load of course.
They run a pair of 8122s driving a pair of 4CX1500A finals, geez!!!

 

[Mogman]

Turns out there are allot of spray in RF shielding products, time to do more research!!

 

[G744]

Yes, I used a silver-bearing paint to do an economical Faraday shield at a high power broadcast facility.

They normally sell it for use in turning blow-molded plastic into silver coated resonant chambers for microwave amplifiers.

It resulted in transforming a concrete block wall into metal, with less than an Ohm/in2. Got it from Carroll Coatings in Providence, RI.

Also, I'd use .020X2" copper strap to join RF elements reference to ground, as braid will change impedance as it ages.

Just a bit of free advice from an old timer in the radio biz.

DG

 

[Mogman]

Yes, I used a silver-bearing paint to do an economical Faraday shield at a high power broadcast facility.

They normally sell it for use in turning blow-molded plastic into silver coated resonant chambers for microwave amplifiers.

It resulted in transforming a concrete block wall into metal, with less than an Ohm/in2. Got it from Carroll Coatings in Providence, RI.

Also, I'd use .020X2" copper strap to join RF elements reference to ground, as braid will change impedance as it ages.

Just a bit of free advice from an old timer in the radio biz.

DG

Thanks, I found one company that has several products, their copper bearing coating they say is the most effective under 30Mc which would be my main concern, they also have a silver bearing coating but of course it is much more expensive.

My first thought is if I laid out a "cage" made from copper strap (bonded where ever they cross) leaving extra along the edges for bonding to the body then spray the copper coating over that cage that it should be effective.

 

[G744]

Sounds like a plan.

 

[MarkM]

Thanks, I am well aware of sound RF practices, I was a communications/SCADA tech for 37 years.

Then you don't know what you're talking about. LOL

That's a lot of gear to go in the truck. Where are you going to mount it all?

I would love to put a AN/GRC-106 setup in mine but I have an old Kenwood 520S that would fit nicely on the radio shelf and it's a good working unit. A Clansman RT320 would also be a nice compact setup. I have an old Icom IC 25A for two meters.

Keep us updated.

Mark

N1FTC