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Ronzo_volvo_guy
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PostPosted: Wed Feb 17, 2021 2:10 pm    Post subject: Re: HAM antenna placement Reply with quote

I've had very good results with Hamstick verticals on mobiles...a tilt-over mounted on a spring mount, they will survive the occasional hit, and can always be tilted over further. They clearly do need a good connection to the body for the counterpoise.

A quick deployed Inverted V as VN shows is of course nice...and with ends tossed into a tree can be a dipole even.

If I was going QRV Mobile in the Westy (actually my son's), I'd look at installing that springmount on the D Pillar also.

'73 de KA1-RPB
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Vanagon Nut
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PostPosted: Wed Feb 17, 2021 7:00 pm    Post subject: Re: HAM antenna placement Reply with quote

dabaron wrote:
Vanagon Nut wrote:
I've been experimenting with a 20 meter inverted V antenna

that is a respectable setup. dragging the ends out further to reduce the angle at the feed point might lower the SWR and help with the radiation pattern.

what frequency is the antenna cut for? i'll be QRV in the Westy in March


The goal was to cut antenna to ~ 14.200 Mhz but what I did was cut it long then fold back ends by ~ 8" which seemed to lower SWR.

The SWR seems to be affected by inner angle and height of wire ends to ground. In the image that "inner angle" appears wider than 90º. My main concerns: make mast stable, keep wire ends up high away from errant hands et al.

11' mast: 8' x 1" PVC with 4' wood dowel in portion of it near standoff. Last 3' is wood dowel. I plan to try smaller OD PVC with wood dowel. Increasing mast height even by 2' likely won't do much to increase efficiency.

An coax air wound choke at feed seemed to reduce floor noise and IIRC, SWR but the added weight made erecting the mast very awkward and top heavy. But, the mast held up even in moderately windy conditions. I plan to make a toroid type 1:1 current choke.

Decreasing the inner angle closer to 90º seemed to decrease SWR but at one point, likely with the choke and inner angle close to 90º, SWR was very low; the needle on outboard meter was hardly moving; AFAIK, I had it "calibrated" correctly.

On winter field day I ran this V inline with the van body; one element was basically running above van. Other element was in "free air". I made about 5 contacts. I thought the van body would really adversely affect propagation but apparently not.

Ronzo_volvo_guy wrote:
I've had very good results with Hamstick verticals on mobiles...

A quick deployed Inverted V as VN shows is of course nice...and with ends tossed into a tree can be a dipole even.


Yes for sure re: dipole configuration. I'd also be curious how well an EFHW would work using mast as shown. (wire ~ 17' off the ground) More gear would be required of course.

re: Hamstick. At ~ 3:30 PST while operating in the trees, I had QSO with operator in St. George Utah. He was 4/4 or so and was portable with Li battery, 90 Watts, on his Ham stick. His QTH was in a very open area though.

Neil.

my outboard meter

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Bear in mind that this is all prototype stuff. e.g. the 1" pipe is too large for this. i.e. a lighter weight fibre glass mast would likely be better especially if one used ladder line. The coax I'm using is quite heavy. (RG13 something) The cut down PVC T standoff piece fits even with top down. Of course YMMV.

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field day

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PostPosted: Sun Jun 06, 2021 12:45 pm    Post subject: Re: HAM antenna placement Reply with quote

Hi all.

edited.

I've abandoned the 20 meter inverted V dipole supported by mast on van concept. But, an ~ 8' mast on luggage rack *should* support a flat top dipole or end fed "random" length wire. Various forms of a 20 meter 1/4 wave vertical wire off a mast mounted to van "worked" but need further testing. I came up with a proof of concept means to help raise the mast using threaded rod on turnbuckles attached to luggage rack. It helps but raising a mast with end in luggage rack, attaching it to the van, is risky especially if mast is 12' or longer. YMMV. OTOH, setting up an awning can be risky. Some coax feed line, e.g. RG213, can add a significant amount of weight.

I carry a jack stand and piece of wood on long road trips. The 8' white PVC is filed at sides to fit jack and end passes through a hole in wood base. Jack stand straps to wood base. On level ground, base supports the mast as-is but I always weight it down with log or rocks. A large water container might do same. In windy conditions, base weighted, the mast will sway but so far, has not fallen down. That said, I have run 1 or 2 guy ropes to the mast. I carry a telescopic xmas light hanging pole. It can act as a mast or part of a mast but should serve to help hang the vertical wire from a tree.

I'm not using air wound choke shown. Feed line is ~ 28'. With or without that choke, SWR and reflected power are quite low but I don't know what the antenna efficiency is. But, I've made many QSO's from the Sunshine Coast some being DX. e.g. Barcelona, New Zealand so it for sure works ok. I often get compliments on audio quality.

My Fishing Pole 20™ (joking about the ™)

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I've used the four 8' insulated radial wires above ground, at an angle and on the ground. The latter works best for me. Feed point is at ground level. Coax feeds into and secures to a grey PVC T. Each wire is soldered to coax, knotted for strain relief then pass through a hole in T. Vertical feed is as close as possible to radial connection (center where radials form a +). I usually use a rock to weigh down the T. Radial wires (junction) are removable to allow connection of a 16.5' wire to form a dipole. My goal: make an affordable DIY antenna that erects almost anywhere and is stable under most conditions. AFAIK, even 100 Watts power can pose a potential risk of RF burn at the antenna which includes the radials. I'll try running the lower half of vertical inside the white PVC pipe. Not sure how, if, I'll protect the radial wires but I do clear away combustable material from them before laying them down. When I operate, I keep an eye on the area around the antenna.

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PostPosted: Wed Jun 09, 2021 7:33 pm    Post subject: Re: HAM antenna placement Reply with quote

Midknightc3 wrote:
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?

They dont cover it much in the Tech manual, but you need to understand there are two issues: grounding and ground plane. They arent the same. You can have a ground plane that isnt grounded and a ground with no ground plane. You can also have your radio finding a ground or ground plane that you dont intend, through covalent bonding

All antennas need grounding. Some will work without a ground plane but almost all VHF/UHF work better with a good ground plane.

I used to work at an ambulance service with fiberglass tops onnthe tops. We had to add a metal ground plane on top before they worked well.

Some other concepts you need to understand is the roof is always the best location Windows, fenders, bumpers anywhere else is always a compromise because some part of the height of the antenna is blocked to some extent. Obviously the antenna would be directional too with the part of the vehicle that is blocking the RF. Whether it matters or not is another question. My father still runs a dual band glass mount and it still works well enough to hit all the repeaters he wants to work.

The ARRL antenna manual is a great resource, even though most pertians to HF.
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PostPosted: Wed Jun 09, 2021 7:58 pm    Post subject: Re: HAM antenna placement Reply with quote

nemobuscaptain wrote:
I used to work at an ambulance service with fiberglass tops onnthe tops. We had to add a metal ground plane on top before they worked well.


I was wondering about this recently.

As a kind of hypothetical, if a 10 meter 1/4 wave vertical was mounted to the pop top (used when down) for "in camp" use, assuming the body parts are bonded properly, would bonding the feed line coax shield to the body suffice to provide adequate ground plane?

I'd guess that a 1/4 wave vertical with 4 angled radials might work but I wonder how the vans' body metal might interfere with that.

Edit: I've been thinking of ways to mount a 20 meter 1/4 wave vertical to the top of my Westy but even if I found means to safely raise it for "in camp" use, I'd hate to put time into figuring that part out if the body metal, properly bonded, won't provide a decent, or any, ground plane.

Neil.
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PostPosted: Wed Jun 09, 2021 8:03 pm    Post subject: Re: HAM antenna placement Reply with quote

Vanagon Nut wrote:
nemobuscaptain wrote:
I used to work at an ambulance service with fiberglass tops onnthe tops. We had to add a metal ground plane on top before they worked well.


I was wondering about this recently.

As a kind of hypothetical, if a 10 meter 1/4 wave vertical was mounted to the pop top (used when down) for "in camp" use, assuming the body parts are bonded properly, would bonding the feed line coax shield to the body suffice to provide adequate ground plane?

I'd guess that a 1/4 wave vertical with 4 angled radials might work but I wonder how the vans' body metal might interfere with that.

Neil.
Oh. Way beyond me. Im no Elmer by any means, and I have little actual HF experience.

My off the top of my head guess would that it would ground if you ground the coax to the body but it would not ground plane well with the vehicle under it, just from military vehicles under wire antennas.

I dont think fiberglass shields. Stealth antennas placed are placed inside fiberglass as are hamsticks or CB antennas. Fiberglass just isn't a ground plane.
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PostPosted: Wed Jun 09, 2021 8:47 pm    Post subject: Re: HAM antenna placement Reply with quote

nemobuscaptain wrote:
Vanagon Nut wrote:
nemobuscaptain wrote:
I used to work at an ambulance service with fiberglass tops onnthe tops. We had to add a metal ground plane on top before they worked well.


I was wondering about this recently.

As a kind of hypothetical, if a 10 meter 1/4 wave vertical was mounted to the pop top (used when down) for "in camp" use, assuming the body parts are bonded properly, would bonding the feed line coax shield to the body suffice to provide adequate ground plane?
Oh. Way beyond me. Im no Elmer by any means, and I have little actual HF experience.

My off the top of my head guess would that it would ground if you ground the coax to the body but it would not ground plane well with the vehicle under it, just from military vehicles under wire antennas.

I dont think fiberglass shields. Stealth antennas placed are placed inside fiberglass as are hamsticks or CB antennas. Fiberglass just isn't a ground plane.


Well, over the last while I've been "forced" to learn more about antennas, which is really good. Regardless, "I know enough to get in trouble". Wink I was likely comparing apples to oranges somewhat but having a 1/4 wave 20 meter antenna on the roof would be ideal for in camp use. Out of harms way and all that.

Thanks for mention of military vehicle antennas. Something else to check out I'm sure.

No. Did not think the fibreglass top would block signal propagation. And yes, my thinking is that the pop top would lack the ability to provide any real ground plane. (simulated ground aka "other half of antenna")

This page:

https://www.electronics-notes.com/articles/antenna...rtical.php

certainly backs up what you found in real life experience. I still wonder though if the entire vehicle body has some capacitance "connection" to the earth and that that figures into establishing a ground plane.

From the above linked page:

For VHF and UHF installations, height is obviously important and antennas need to be raised to ensure they are above the nearby obstructions. Also for mobile installations it is clearly not possible to use a true earth connection. In these cases a simulated earth is used. For mobile applications this consists of the body of the vehicle. The antenna mounting will normally enable a suitable connection to be made to the vehicle body, sometimes using a capacitive connection. However it is necessary to ensure that the vehicle body is metal, and not plastic in the vicinity of the antenna mounting.
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PostPosted: Wed Jun 09, 2021 9:55 pm    Post subject: Re: HAM antenna placement Reply with quote

Vanagon Nut wrote:
Well, over the last while I've been "forced" to learn more about antennas, which is really good. Regardless, "I know enough to get in trouble".
Exactly. We crosstrained in the military, Im a tech now, and I've worked with VHF and UHF commercial vehicle radios good deal for decades. I can usually fix the easy stuff, but I shy away from components etc.
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PostPosted: Thu Jun 10, 2021 9:51 am    Post subject: Re: HAM antenna placement Reply with quote

If it's safely possible, I'll try my current vertical 1/4 wave on top of my westy pop top. I'd connect the coax to the body.

If I ever make a wire vertical for "in camp" use I'd like to locate the elements away from easy reach. e.g. maybe run the four 8' radials under a "grass" matt in front of the bus. But, I don't know how much, if any risk, there is for voltage at radials to ignite matter on the ground.

On 100 Watt solar + group 31 SLA battery, I usually limit RF power to 75 Watts or less. But even at 75, I work on the assumption that there is some risk of RF burn to someone touching the antenna wire(s).

Neil.
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PostPosted: Mon Jun 14, 2021 12:12 pm    Post subject: Re: HAM antenna placement Reply with quote

Here's our June 2021 ARRL VHF contest setup. We operated as KA5D in the Limited Rover class.

The top photo location is Devil's Backbone, near San Marcos, TX. Supper was beef tostadas with fresh avocado and cold beer.

I'm explaining to some bystanders what ham radio contesting is. They thought we were storm chasers or ghost hunters (the overlook is a popular spot for scattering human ashes).

The bottom photo shows how it all looks with our top down and masts collapsed for driving.

We won 1st place nationally in Limited Rover class in January, and it looks like we will win 1st place nationally again in June.

kourt

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PostPosted: Mon Jun 14, 2021 9:35 pm    Post subject: Re: HAM antenna placement Reply with quote

kourt wrote:
I'm explaining to some bystanders what ham radio contesting is. They thought we were storm chasers or ghost hunters ... We won 1st place nationally in Limited Rover class in January, and it looks like we will win 1st place nationally again in June.


That's awesome in so many ways. Especially the Ghost Hunter comment. Wink

Great to see your antenna systems.

Way to go!

When will someone start a VOTA?

(Vanagons on the air)

Neil.
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PostPosted: Thu Jun 17, 2021 11:28 am    Post subject: Re: HAM antenna placement Reply with quote

kourt wrote:
Here's our June 2021 ARRL VHF contest setup.


Hi Kourt.

Seeing your antenna farm mounted on a Westfalia is inspiring.

I guess it wouldn't take much to try this out but....

For Kourt or anyone else...

If a 20 meter 1/4 wave wire or aluminum rod vertical was mounted on the Westfalia luggage rack, would bonding the feed line coax shield to the van body (assuming the van body sheet metal is all bonded well) provide a ground plane that might keep SWR below 1.5 ?

I'd be using a maximum 100 Watts RF power but more likely 50 Watts or less.

Neil.
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PostPosted: Thu Jun 17, 2021 11:39 am    Post subject: Re: HAM antenna placement Reply with quote

I'm pretty confident that would work.

My 102" whip antenna is mounted on the rear steel bumper, in an NMO mount drilled into the steel. That's the ground plane connection.

I use that antenna on several bands from 10 meters to 40 meters. I hit Italy on 40 meters with it once.

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PostPosted: Thu Jun 17, 2021 11:56 am    Post subject: Re: HAM antenna placement Reply with quote

KC3DOO checking into the net

Mounting an antenna without a ground plane strikes me as why bother.

Assuming that the fiberglass top will endure some abuse is ... um... ill-advised. DAHIK

73's KC3DOO out
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PostPosted: Thu Jun 17, 2021 12:22 pm    Post subject: Re: HAM antenna placement Reply with quote

RBEmerson wrote:
KC3DOO checking into the net

Mounting an antenna without a ground plane strikes me as why bother.


net control,

no ground plane is no good, and you really want a solid physical connection location. there is always a tree branch you won't see. a mount for hamsticks or a whip on a metal bumper seems to be the best option for protection and RF radiation while under way.

if you are just looking for a mount while stationary, a mast in a bracket held in place with the driver's side rear wheel is a great option.

73 de K3LID.
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PostPosted: Thu Jun 17, 2021 12:23 pm    Post subject: Re: HAM antenna placement Reply with quote

Thanks Kourt. Very helpful.

I've had really good success with my "20 meter fishing pole" vertical wire I made. I've gotten into Europe and other DX. Even some local QSO likely via ground wave propagation and favourable band conditions. That said, my portable QTH is ideal. Mounting something similar on top of van would certainly help put the antenna out of harms' way. e.g. for use at VW campouts.

This image shows a kind of proof of concept. If I rigged up a pulley, or even just a rope, I think i could safely erect a 16.5' aluminum vertical. I did use this to erect and support my PVC/bamboo 20 meter 1/4 wave mast. Top up, it could rest against the top. Top down, well, don't know yet. I also don't know if having radiating element relatively close to transceiver (or me!) is a bad idea. I'm learning to run lower power so I doubt its a potential issue.

Neil.

ignore the rusted bracket. Rod would be longer. Metal nipple was filed down a bit to fit ID of PVC mast. Edit: as per my previous comment, I'd use an aluminum vertical not the PVC/bamboo arrangement I have shown. I'm pretty sure ~ 1/2" aluminium tube would be lighter.

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this is the general idea. This mast is too long, heavy. Do NOT attempt ! I attempted multi band use with coupled to an Icom AH-4.

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PostPosted: Thu Jun 17, 2021 3:06 pm    Post subject: Re: HAM antenna placement Reply with quote

Guys;

On my mobile, a '66 Volvo, on the C pillar (obviously metal), I have a heavy duty G-E spring, with a Hustler fold-over mount and finally a Hamstick for the band I'm working*, including mobile. I think a such a spring mount with Hamstick would work well on the D pillar of a Westy...it into structural sheetmetal also and IF you go under a low roof at a gas station, the spring saves the day. Normal overpasses are typically at around 14ft.

...not quite like this, but I thought you might get a chuckle out of the pic...:

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Just as a reference, an antenna mount in the fiberglass of a Westy would be fine too...just add a 1" braid (low L!) back to the vehicle sheetmetal for that counterpoise...which is required only for verticals...and would not be required if your vehicle had for instance only a center support mast for a balanced fed inverted V (the ends supported by trees), but that would clearly not be for mobile operation.

*Powered by my Icom-706, I once QSOed with a JA on 20M from my driveway in Connecticut, and during a snowstorm! The fact that he called "listening for 1s only" helped, because the 6s, which I would have had no chance against in the pile-up, were nice enough to wait...I thought it was pretty cool mobile QSO!

73 de KA1-RBP
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PostPosted: Mon Mar 20, 2023 4:01 pm    Post subject: Re: HAM antenna placement Reply with quote

Apologies if already discussed, quick key word search didn't show....

If RF path was good through hinge to body, for an HF vertical.....

Make a 2 or 3 point mount bracket that attaches to rear hinge bolts, use a 1/4 wave vertical with that? A ham stick would be quick and easy.

I'm thinking more for "in camp" type work. Vertical could be pivotal. I'd guess that unless loaded, 20m might be the limit for length.

Neil.
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PostPosted: Mon Mar 20, 2023 7:13 pm    Post subject: Re: HAM antenna placement Reply with quote

Well, it's not a Vanagon, but perhaps this can provide some inspiration.

My Thule roof-rack had an accessory that was a single upright post. I think it was supposed to be for stabilizing kayaks. Anyway, a section of ordinary (in those days) TV-antenna mast slid nicely over that post.

I used three 8' sections to achieve a 24' centre support, which was driven through a tuner by 600Ω ladder-line. The wire was cut as an 80 metre dipole. I could work 80-10 metres with the tuner and near-unity SWR. (No telling what the radiation angle was! Part of the adventure!)

With a balanced dipole, I didn't have to worry about ground counterpoise. I started off feeding it through an MFJ tuner similar to this one, but replaced it with an Icom automatic tuner with a simple homebrew UNBAL feeding the ladder line.

The mast was guyed at the 8' level to front and rear bumpers. The ends of the dipole were attached through an insulator to a dozen feet or so of bungie-cord material, which I could tie to anything nearby, or even tie to a rock.

This obviously wasn't for use while travelling! But it only took minutes to set up when camping. The operating position would have been much nicer in a Vanagon!

On the cab roof is a VHF-UHF trap vertical.

de N7JDB

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