Amateur radio antennas

[ai4kk]

I'm building up a Prius V as a camper and working on aerodynamic wheel covers, fender skirts, and a boat tail. I'm also a ham radio operator and plan to have a couple of radios in there both for on the road use and also as a temperature sensor / transmitter for keeping tabs on the temperature inside since my dogs will often be staying in the car with the air conditioning on.
Where do radio antennas fit into aerodynamics? I'm looking at at least one 8 and 1/2 ft whip and two more traditional 2 m antennas about 48 in long.
I've seen some other hams on here, have any of you all paid any attention to the aerodynamics of your antennas or have you just accepted that loss as part of the cost of the hobby? Do you know what kind of things can be done to antennas to make them more aerodynamic? Not so much concerned about the whip part as the junction with the body

[ai4kk]

Thinking about this a little more and thinking maybe the answer is to use foam and fiberglass to sculpt leading and trailing edge fairings for all antenna mounts to make them more airfoil-shaped instead of just a big ball sticking out the side of the car

[freebeard]

...instead of just a big ball sticking out the side of the car.

It's been like a half-century since I studied electronics, but IIRC the antenna can be amplified by a ground plane. Like the roof of your car.

As for the junction -- fillets and blisters.

[redpoint5]

I just started taking practice tests for the technician license and it seems I probably won't need to study too much to pass it considering there's a lot of basic electronics theory in there.

I'd say get the skinniest antenna that will hold up to your use case, and then sculpt a trailing edge device of some sort. I'm envisioning something like a straw with a tapered trailing edge that inserts over the antenna. It would make it rigid though, which makes it susceptible to damage. The ideal solution would probably be made of foam.

[freebeard]

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https://live.staticflickr.com/8188/8...78e648bf14.jpg

Four foot trolling rods, but the 8.5ft mast should be stowable for freeway speeds and parking garages. [IMHO]

Tiny little vortex-killing T-tails on the 2 meter antennae.

[Isaac Zachary]

Number 1 way to make an aerodymanic antenna: remove it while driving.

Personally I just accept the loss. You aren't going to get a 8.5ft whip to work that's only 1/32 of an inch thick. You also need the diameter for current, which is also limited due to the skin effect.

It might be possible to make an antenna that has a "tear drop" shape, but I'd be afraid that regardless of how you made it, it would have too much strength front to back and not enough side to side, coupled with greater weight. In other words, it may sway and flop all over like a tape measure (only stiffer) and not give to wind and velocity changed, which will probably bend the heck out of the mount.

But hey! Amateur radio is also about expirementation. I've thought about trying some sort of "tear drop" shaped antenna, but I don't have the time right now and don't see the benefits outweight the costs yet. I just did a 400 mile trip and averaged over 46mpg in a full sized car (Toyota Avalon HV) even with the 1/4 wave 70cm/2m antenna on the trunk. When I get my HF antenna NMO mount put on the top I'm going to be taking the antenna off as I drive, since I only do HF at night while stopped and also use different antennas for different bands anyway, including one 15ft telescoping antenna that would not survive me driving around at highway speeds with.

[freebeard]

Not so much concerned about the whip part as the junction with the body

Nobody is addressing this point. The examples I gave are fixed. Here's how we dd it back in the day:


https://external-content.duckduckgo.com/iu/?....&ipo=images

If the antenna mount is at the rear of the boat tail, 8.5ft would come to where? The windshield header?

[Isaac Zachary]

Originally Posted by freebeard

It's been like a half-century since I studied electronics, but IIRC the antenna can be amplified by a ground plane. Like the roof of your car.

Originally Posted by freebeard

Nobody is addressing this point. The examples I gave are fixed. Here's how we dd it back in the day:


https://external-content.duckduckgo.com/iu/?....&ipo=images

If the antenna mount is at the rear of the boat tail, 8.5ft would come to where? The windshield header?

An ideal ground plane would be to put the antenna right in the middle of the roof. Putting it at the rear of the car would be a compromise as it would have less "amplification" (gain) towards the rear.

But it all depends on what is trying to be achieved here. How much of a compromise? A shorter antenna can also be a compromise.

[aerohead]

I'll advocate for streamlining the bases, and unscrewing the antennae while commuting, re-installing at destinations.
Somewhere, there's a comparison between a streamlined strut and cylindrical structure drag ( I think it's in Hermann Schlicting's book, Boundary-Layer Theory' ).
You'd 'lose' the antennas if you saw the difference.

[freebeard]

If the antenna is to be removed, and the top center is the optimal location, why not a flush threaded [electromagnetically isolated] hole?