HAM antenna placement

[Midknightc3]

I know this has been covered, but after reading many threads no one has discussed what I was planning, which has me worried. My plan is to place a dual band antenna on the forward center lip of my pop-top with a Diamond K400. My idea here is I can fold the antenna down when not in use, but this gets it nice and high for driving to and from a camp site, and once in camp gets it that much higher with the tent up.

Is this a bad idea because the fiberglass is likely to be damaged if I whack a tree or some such? Really my main interest for this location is the added height when in camp, but I have other ways to achieve that if this is a bad idea.

Thanks!
Clark

[Gnarlodious]

Game over, this guy wins! First post in eight years!

de K5ZN
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit

[Zeitgeist 13]

Paging Dr. Kourt...paging Dr. Kourt...

[dabaron]

K3LID here...

how you want to operate is an important factor. are you 2m and 70cm repeater hopping?

i don't think the rubber will be up to the task of supporting the load. a better option is to accept the height of the bus and use the luggage rack screw mounts as an antenna mount point. take advantage of the gutter and use a gutter mount and run the coax down the driver's vent in the rear.

i plan to operate HF from my Westy to a 20/40M wire.
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1991 Vanagon GL Camper
i had no idea i wanted to be a mechanic
"burnin oil and cookin coils" -- Destructo

BiWerks Design, LLC

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[Midknightc3]

Haha! I had not realized it had been 8 years since I joined! That must have been when I obtained my Westy from my uncle, who had purchased her new in 1990. I come from a 4x4 background, and also own a 1986 Toyota FJ60 I lovingly call the Wandering Goat. She has been my primary mode of more local travel, and thankfully the Vanagon has just been there, trustily running when I need her, which is why I have not been posting here. Due to COVID however, we have stopped our international travels, and wanting to focus more on hiking than wheeling, the Vanagon is taking more front stage.

[lcolon]

I actually purchased one of the VanagonLife MPV vents that has both an external solar panel plug and an antenna mount. It is designed to use a firestik M2 mount which is a 3/8x24. You can get many ham antennas using those threads.

That is my plan for when I finally put a ham radio into my van. For the moment solar panels and the ham radio later.

On my landcruiser I use the K400 lip mounts to the tailgate lid and they work very well. I am not willing to use those on my van given the new paint job. Should work well, however. On my cruiser I have one side with a dual band 2M/70CM and the other side I have various hamsticks that I use (20m, 40m, 6m) depending on what I am doing.

The one thing I do not like about the fiberglass is that the antenna would not be grounded up there and you will likely need to use some sort of grounding braid to the chassis. The vehicle is half of the antenna. This is more important with HF than VHF/UHF depending on what you have in mind.

Also keep in mind, depending on how you do things, the K400 only changes position by getting an hex wrench out, loosening the mounting bolt, and adjusting the antenna angle. If it was on the fiberglass roof, you would need to climb up there and adjust it for roof closed vs open to get it vertical.

Luis AF6GS

[MarkWard]

If you do use the fiberglass top, you could back it up with a decent metal plate from underneath. A smaller plate could be at the base to sandwich the fiberglass. This might improve the ground plane for the antenna too.
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[kourt]

Greetings!

If it were my van, I would not install anything into the fiberglas poptop, especially on the edges.

I see the appeal of getting the antenna on the roof. However, the extra elevation gained from getting the poptop open at your campsite isn't really meaningful. The poptop is relatively fragile and hard to replace. If you hit a low tree branch, the weakest material in the chain of materials will absorb that energy. Your poptop mount may not fail the first time, but it will fail much less gracefully than sheet metal.

On top of the relatively poor mechanical foundation, the poptop has poor electrical grounding, and your feedline has to be run through extraordinary means to make this all happen.

I still stand by my idea of using the sheet metal around the engine vents, or the D pillar, to install antennas. I've been doing it that way for about seven years. The back sides of that sheet metal are easily accessed through the engine vents (for support plates behind the mounts) and the vents themselves offer a clean passage for the feedline (no new external cuts to your body metal).

I recently bought this Larsen 90 degree NMO mount for a cell phone booster. I mounted it just forward of the engine vents. It's a great way to mount an antenna to the sheet metal, get it high up and get it grounded.

If you're only going to mount one antenna, I suggest using the driver side D pillar. Low tree limbs are less prevalent on the driver side of the van, since that is usually the middle of the road. This will keep the antenna strikes from tree limbs down to a minimum.

The bottom photo in this post is an example of an NMO plate I'm still using, bolted into the top lip of the engine vent. If you need a part number for this plate, message me.

The above post referring to a rain gutter mount is also a good idea.

Summary: don't mess with the poptop fiberglas. Do use the D pillar sheet metal area to make something happen.

I hope this helps.

kourt
KB5PRZ

[bsrad]

I don’t know if you have “truck style” mirrors but we’ve been running this one for over three years and and love it. It’s really nice to be able to reach out the drivers window and fold it down if you have something hanging down like a tree limb the you want to get under.
https://www.amazon.com/dp/B00NWYVM94/ref=cm_sw_em_r_mt_dp_TXg9FbWP8KR0Q?_encoding=UTF8&psc=1

https://www.amazon.com/dp/B00IDTJ1VY/ref=cm_sw_em_r_mt_dp_67g9FbKFZ5B0N?_encoding=UTF8&psc=1

I’m not an expert by any means but works great for vehicle to vehicle communications. And FYI we too run the FT7900. Let me know if you want any pictures.
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Bill

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1987 Syncro Westy
1967 OG Single Cab
1976 FJ40

[Steve M.]

[GoEverywhere]

I have my 2M/440 antenna mounted at the top of the rear hatch on a lip mount.

Its important to have good metal contact for the antenna's ground plane, so sticking it on fiberglass is going to lower the performance of the antenna. Since my van is a poptop and its fiberglass everywhere, the rear hatch made the most sense.

[1988M5]

Thought; Spray copper head gasket seal then aluminum tin-foil to the bottom side of the fiberglass top to achieve the "ground plane".

BK
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1991 tin top GL
2002 Winnebago Vista. VW VR6 24V Eurovan front clip powered class C 21' RV.
Some BMWs.

[Midknightc3]

So y'all have me convinced not to mount it to the fiberglass lip, I assumed strength was the reason this hadn't been discussed and it sounds like that is the case. I already have the K400, so I will probably run with something on the rear hatch. As for ground plane, I am running a Diamond NR770HB for most applications, and a Commit SS-460SB when I'm expecting clearance to be an issue. On the Goat (FJ60) the mount is on the drivers side hood/fender seam. Both of these are intended to be mounted in such a way that grounding isn't specifically necessary right? I know it's still a factor, but I have been of the assumption that overt grounding of the mount isn't necessary with these antennas. While I have been operating HAM for many years, I still have loads and loads to learn!

[Midknightc3]

Mounting to the engine vents is certainly an intriguing idea. I had seen kourt's images of his mount and had already been keeping that in the back of my mind, but perhaps I should advance that idea over the K400 on the rear hatch, since opening the hatch wouldn't affect placement. I can always use the K400 on the wife's Subie for our road trips, though it's probably overkill for that application.

Icolon, I had not been aware of the Vanagonlife vents, but that is a slick setup. I currently have a rigid solar panel that I have wired to work with either the Goat or the Vanagon, but have definitely considered a more dedicated setup for the Vanagon, and that antenna mount is quite slick.

I'm now deep in debate with a buddy of mine about ground planes with these antennas, something I have had a hard time wrapping my head around in the past as well.

[tjet]

I installed a 102" whip on a ball-type mount on the LH rear side below the window. Mast is currently removed.

https://www.thesamba.com/vw/gallery/pix/2093131.jpg

[kourt]

I am presently using two Diamond NR770HB antennas on my van, one mounted to each engine vent.

I can hit my UHF repeaters in Austin with 50 watts from 60 miles away with these antennas (Yaesu FTM-300DR).

They are excellent for the van in that they can be easily folded down. I do this a lot when I need to get boats and other loads on the roof racks.

Mine take an almost daily beating from tree branches. The engine vent mounts I have from Larsen take any energy and deform as intended, and bend back into shape easily.

Any and all vertical antennas require grounding. One must consider all vertical antennas to be half of the entire antenna system, the other half being the best ground you can offer.

Conversely, a dipole is an example of an antenna that does not require a ground.

In the case of the Vanagon, or any vehicle, the best ground is body sheet metal. I have seen some creative suggestions for poptop grounds in this thread. They are well intended, but all terrible ideas! They all would add mass to the roof, add corrosive materials, permanently modify the poptop finished surfaces, or worse--and the ground planes they would offer the vertical antenna element would be sub-par compared to the body sheet metal

Summary: the metallic vertical antennas you buy are only half of the system, with the other half being a metallic ground you supply. If you are not grounding your vertical, you are not offering the radio a balanced emitter for RF energy. New poptops are not being made, so tread lightly on any ideas of modifying one.

kourt

[Steve M.]

https://forums.qrz.com/index.php?threads/dual-band-antenna-grounding-for-fiberglass.697717/

https://ham.stackexchange.com/questions/8885/cb-ground-plane-on-fiberglass-rv

The question is whether or not your antenna requires a ground plane?
Some do and some don't.
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[Vanagon Nut]

I've been experimenting with a 20 meter inverted V antenna that mounts to a mast supported at luggage rack and raised pop top. Since I'm "forced" to work portable from my van, I can pick advantageous spots which really helps (see below) but so far, it's working quite well even at the side of a dirt road with a bunch of trees around.

Feed point is ~ 16' high. With inner angle at more than 90º, dipole ends can be ~ 10' high.

This antenna can obviously be used as a horizontal dipole but if the improved lighter weight mast I'm thinking of pans out, I'll be curious to see if I can "shorten" the antenna by folding the wires back on themselves so it can be used as an "up and outer" L wire antenna on 15 or 10 meters. One external securing point would be needed for horizontal element.

This is not the final version of mast etc. YMMV. I was up the mountain with a wide clear view of Pacific ocean so in a lot of ways, the QTH was ideal. Best QSO was Japan albeit difficult to work. (100 Watts, phone)

view

Neil.
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1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[dabaron]