OEM Antenna Shortened to 17" or 24"!

[OLDMNSX]

So who would like to have a 31" OEM antenna shortened to either 17 in or 24 in? Sorry, no other choices. No modifications to the mast required.

If you want it to come up 17in, it is really easy. All you have to do is remove the antenna motor housing and rotate it 180 degrees. This changes the polarity of the magnets and makes the motor run backwards. The timing wheel inside then limits the travel of the antenna mast. The first time that you actuate the antenna after this procedure causes the clutch to slip until it reaches the stop, then it will only come up 17in. Really easy. I haven't done a reception test on either of these. Obviously if this doesn't work for you it can be reversed really easy, not like a vasectomy.

If you want it to come up 24in this procedure is much more indepth. Remove the antenna, remove the back cover, NOT THE ROUND ONE. Remove the two small gears, remove the timing wheel and assembly. The timing assembly is held together with hook arms on the back. Look at the back side. Carefully split the two pieces and remove the timing wheel. Take a small Dremel or like tool with a side cutting wheel and trim the timing wheel to the frist anchor point going counter clockwise from the null. Thim out this piece and smooth the cut edge. Stick it back together and now you have a 24in OEM antenna. This procedure is the vasectomy. If you don't like it you will need another timing wheel to replace the one that you cut up.

Brad

 

[ChopsJazz]

You could also buy the Integra (I think) replacement mast as I did. It's a few inches shorter and it's a direct fit.

 

[warrenw]

Brad, this is interesting.
How is the radio reception at 17"?

 

[OLDMNSX]

How is the radio reception at 17"?

Warren,
This has been one of those projects that I finally got around to doing this winter so don't have any data on the reception. My car is up on jacks with the tranny disassembled on my work bench and I just scooped 3" of snow out of my driveway before coming to work this morning. When is the snow going to STOP?
Brad

 

[warrenw]

Warren,
I just scooped 3" of snow out of my driveway before coming to work this morning. When is the snow going to STOP?
Brad

Around here it is late April early May
The good thing is you get that new car feeling every spring! That's about it though.
Thanks for the info

 

[Quix-Draw]

I'm trying to think... What is snow?

 

[nigel]

A four letter word.

Cheers
nigel

 

[angus]

So ... who knows the theory behind the 31" antenna length ?

nsxprime trivia!

 

[OLDMNSX]

So ... who knows the theory behind the 31" antenna length ?

nsxprime trivia!

By rotating the magnets on the motor 180 degrees you reverse the polarity of the motor which reverses the direction that it rotates. This in effect causes the "timing wheel inside the antenna to rotate backward and so the "nulls" on the wheel occur sooner. Give it a try, it is totally reversible. The 31" length is just the result, nothing scientific about getting it.
Brad

 

[FastraxTurbo]

31" used to be the 1/2 wave length of the frequency spectrum for AM reception. For FM, it doesnt matter as much since most of your stations are local and signal is strong. If you're in rural areas, then a longer length is better, as FM signals cannot follow the horizon.

 

[Ryuji]

Hello,

I just tried the 17" method and a strange thing happened.
OK, the antenna goes up only 17" BUT
when the radio is off, the antenna goes up
and when the radio is on, the antenna goes down...

Is there something else to do other than rotate the motor
housing ?

 

[dquarasr2]

Can I ask a naive question?

Why is shortening the mast considered a good thing?

 

[Ryuji]

Why is shortening the mast considered a good thing?

Look :biggrin:

 

[ChopsJazz]

Contrary to popular belief, longer does not look better. Unless you like flagpoles. :wink:

Hello,

I just tried the 17" method and a strange thing happened.
OK, the antenna goes up only 17" BUT
when the radio is off, the antenna goes up
and when the radio is on, the antenna goes down...

But this is some funny stuff. :biggrin:

 

[Ryuji]

By rotating the magnets on the motor 180 degrees you reverse the polarity of the motor which reverses the direction that it rotates.

Reading again all the thread, I found this that perfectly
explain what happened to me...
So the 17" method is perfectly useless :biggrin:

 

[9doors]

Yes...I had a similar experience 'till like a fool I kept fiddling with it and I had forgotten to pull the fuse relay under the hood, sparked the motor housing at one point and now it no longer works at all...

I'm thinking I just blew up a $400 antenna:frown:

 

[OLDMNSX]

Hey guys,
I am sorry you are having problems with my suggestion. I will take another look at what I did and see if I have left something out of my directions.

9doors if you have checked your fuse and it is good, send me your antenna and I will fix it for you. PM me and I will give you my address. I have another antenna already modified to come up 24 in, and it works just fine, and I can just send you that one if you would like.

Sorry for your trouble,

Brad

 

[drew]

The length 31" is approximately 1/4 wave length for FM at the low end of the scale. It can matter a lot, depending on signal strength and reflection.

Wave length for AM is dozens of meters long, you'd need to trail a balloon antenna behind you to get 1/4 wave length.

The NSX was a function over form sports car. The antenna is more of the same, be proud of it.

Function should always trump form....which why I always think that military hardware always looks amazingly cool.


Drew

 

[latzke]

So ... who knows the theory behind the 31" antenna length ?

The length 31" is approximately 1/4 wave length for FM at the low end of the scale. It can matter a lot, depending on signal strength and reflection.

Wave length for AM is dozens of meters long, you'd need to trail a balloon antenna behind you to get 1/4 wave length.

The NSX was a function over form sports car. The antenna is more of the same, be proud of it.

Fun: http://eosweb.larc.nasa.gov/EDDOCS/wavelength.html
1/4th of FM87.5's wavelength = 33.72"
1/4th of FM108.0's wavelength = 27.33"
(range is 6.39")

Maybe the effective length of the 31" NSX antenna is a little longer (actually 34" with 3" of element being made up of the base)?

I faintly recall seeing first hand the antenna on a 1990 LS400 adjust itself to a couple/few different lengths depending on where in the FM band you were tuned to. My recollection could be faulty...or maybe a 27.33" antenna makes less wind noise than a 33.72" antenna and they were really that anal (in later years they eliminated the external antenna completely in continued obsession with noise reduction).

 

[OLDMNSX]

Reading again all the thread, I found this that perfectly
explain what happened to me...
So the 17" method is perfectly useless :biggrin:

You are EXACTLY CORRECT. When I discovered this procedure of reversing the motor housing I was using my antenna bench test wiring harness that I made. I had not tested it in the car. I have since continued to experminent with this procedure and it DOES NOT WORK. SORRY GUYS, but the other procedure does work. You have to trim down the timing wheel to get the shorter length.

I repaired "9doors" antenna yesterday and trimmed his timing wheel and it works just fine and only comes up 17", so this procedure can be done for both a 17" and 24" length.

If you don't want to cut up the timing wheel from your NSX antenna, go to the salvage yard and get a timing wheel out of a broken Honda Accord antenna.

Brad

 

[9doors]

Just installed my antenna so graciously repaired and altered by Brad.

Looks perfect, works perfectly.:biggrin:

Brad is a stunning example of why Prime is one of the best online communities. :smile:

 

[nh_nsx]

Hey Brad,
I have an antenna question for you. My antenna won't retract all the way. It stops about 2" high. I've tried lubing it with silicon thinking it was sticking but it didn't make any difference.
It's been that way since I bought the car a year ago.
Any suggestions?

Oh, I had it running today and changed the oil and filter. I have the speakers and sub off to Briank to get them repaired.
It was 55 and sunny today here in NH! It's ALMOST NSX time!!
Although the 5 inches of snow we're supposed to get tomorrow could change things.. I still love New Hampshire but I'm getting some serious NSX fever!!
:-(

Thanks!
-Randy

 

[Ryuji]

Contrary to popular belief, longer does not look better. Unless you like flagpoles. :wink:

Just to say that I removed my flagpole to a Shark Attack 2
antenna... And I'm absolutely pleased of the look of that
antenna on my car (short but "virile" :wink: )

 

[OLDMNSX]

Hey Brad,
I have an antenna question for you. My antenna won't retract all the way. It stops about 2" high. Any suggestions?
Thanks!
-Randy

Well Randy what I do with this stuff when it doesn't work, as designed, is TAKE IT ALL APART!

It sounds like there may be something in the mast that is keeping it up a little. If you want to wait till I come out next month, that would give us something to fix, or you can take it out and send it to me.
Brad