Roof Antenna

Because a real vertical piece of metal OUTSIDE the body and the glass makes a better antenna.
Pretty simple really.
That's a "tech" item too.

 

It's called a "ground plane" antenna. The standard 27 inch quarter wave vertical element has been replaced with a 27 inch wire coiled down to about 6 inches.

The "ground plane" is one of the most efficient antennas out there.

When antennas were mounted on fenders, there was inconsistent 360 degrees results in signal strength due to the extreme offset of the "ground."

The center of the roof would have been a better placement. The back of the roof is a compromise for aesthetics.

 

Not sure if it's relevant, but there's one Honda Civic with roof-mount antenna: the hybrid, and it's purportedly due to the hybrid battery causing interference with rear window embedded antenna.

 

And it's a bit more complicated than that, too. A fair number of Priuses come with satellite receivers. There's an amplifier built into the base of the antenna on the inside, likely low noise (first low noise stage sets the overall radio sensitivity), that amplifies not just FM and AM, but that GHz satellite signal as well. If you're going to play with satellites, it's again a lot more fun to have that antenna on the outside.

Interestingly, ye standard 1/4 wave vertical antenna has maximum gain planted roughly around the horizon, with some up-tilt, which works well for the FM radio band, since that's where the transmitting antennas are. However, it's a pretty good bet that the antenna receive pattern for the satellite radio for tends to point straight up where the satellites live. Fun.

KBeck

 

Somehow I doubt that amplifier has any impact on AM at all.
Satellite, sure that's what is mainly there for.
FM, maybe.
AM, highly unlikely as the wavelength is WAY off from the other two.

The 27 inch quarter wave quoted does not even come close for the AM band........where a quarter wave is something like 150 FEET.

 

What, you listen to AM junk?

 

Up here there's CBC am, rebroadcast on fm, just an excellent mix. Nary an ad.

 

I'd be perfectly happy if my prius had no antenna at all. Why would I need one? Do people still use radios? I have an endless supply of music on an ipod. That being said I hated the stupid stick antenna so much I spent the $80 for the fin upgrade. At least now there's no ugly stick on the top of my car and I can run through a carwash without having to worry about the stick getting bent.

 

How serious of a problem is that? Will I be able to take it off easily like I do on my truck?

 

It's probably not a big deal. I'm sure people go through car washes all the time with it on, but I always took it off. It unscrews easily enough

 

Thanks for the reply.

 

Just wanted to chime in here. I do not use the radio AM, FM, or Satellite in my 2012 Prius. I have my iphone with the Tune-In radio app which gives me over 25000 stations world wide, and I use the Pandora app for music. I have Verizon as my cell provider and I never have reception problems...unless I go thru a tunnel.

 

I'm curious. May I ask how much data do you use per month doing that? Going over my data limits might be cheaper than XM.

 

For that matter, the quarter wavelength for a 100 MHz is (3e8/1e8)/4 = 0.75 m in free space; a wire antenna that's resonant at that frequency would be a little shorter (lower speed of light) at around 70 cm. Now, putting an inductor in series with an antenna makes it shorter, and one puts a capacitor at the base to make it somewhat resistive at the resonant point. Further, making the antenna fat widens the bandwidth, a good thing when one is going from 88 MHz to 104 MHz.

To those of you who haven't taken apart an AM/FM radio and discovered the AM antenna, it's usually a low-loss ferrite core loop antenna with a lot of windings on it. Or something that looks like a 6" long, fat inductor. All those windings make it really short. And, yeah, a typical AM antenna has lousy gain, but AM radio stations typically have monster power levels to make up for it. It wouldn't surprise me much to discover that the standard Prius AM/FM/Satellite radio has the AM antenna inside the radio box, but it's probably coming in from that antenna in the rear. Which likely has an "interesting" ferrite in it.

There's an old, interesting story dating back to WW II. In France some GI goes to a techie with his (relatively) high-cost radio, and complains it isn't working well. After a check of the tubes and a tune-up the techie, who just happens to have a 300' antenna out back, hooks up the radio and has the fellow listening to the AM stations in New York. The customer goes away happy.. But he's not going to be listening to any NYC stations with that ferrite rod antenna of his.

KBeck

 

I had a 2011 Prius for 3 years. I ran it through an automatic car wash regularly during that time and I did not remove the antenna once. No problem.

 

No problem...glad to answer your question. I have a 4Gig a month data plan as my wife and I both have iphones. The most I have used so far is 950 meg during the Month of May. That was both of using Pandora alot and me also using my Tune-In radio app. I tried the free 3 month Sirius/XM satellite and that service does not even come close to Tune-In radio. I told Sirius/XM to take a hike. My wife and I are going a a 3 or 4 week road trip end of July thru Aug and I do not expect any issues. Now that being said I do have Version as my carrier and they have excellent cell coverage. When I was still working (now retired) I had a company issued iphone with Sprint as the carrier and it's coverage was terrible. Even driving on Interstate 5 south from LA to San Diego 3 days a week, I would lose connectivity. Never happens with Verizon.

Hope the helps

 

One other thing. My wife and both have non cellular ipads, but we take them in the car and make her phone (which is an iphone 5s and has LTE capability for much better data speed, mine iphone is a 4s and only supports 3G) a hotspot and link the ipads to her phone. Then who ever is the passenger can check their email, surf the web, or watch a movie on Netflix. I do the Netflix thing and have a nice on ear headphone for my ipad. I lean the seat back to a comfortable position, use a pillow as a soft head rest, man it doesn;t get any better traveling on the open road or stop and go traffic.

 

I'm surprised you can do all that with just 4GB!

 

Originally, I didn't think the Prius roof antenna was unsightly or out of date. Recently, I considered going with a shark fin antenna for a better look. Then I had a revelation. Why not remove the mast antenna and keep the base? From a short distance it looks like a variation shark fin
antenna. I NEVER listen to AM-FM, so loss of those signals is no loss. The cost of a shark fin antenna is insignificant, but free is best.

.