NewCelica.org Forum banner
1 - 20 of 20 Posts

·
Registered
Joined
·
248 Posts
Discussion Starter · #1 ·
hey guys, I was reading through some threads and have a question regarding the antenna hookup to an aftermarket headunit. Are there 2 antennas in the celi? I saw a post where someone said to just hookup the bigger one to the new headunit. Does this impact AM radio listening? I listen to AM a lot, so I want as good a reception as possible. If this is going to be a problem, are there adapters available? I am trying to get everything I need before I buy my headunit at the end of the week. thanx, dave
 

·
Registered
Joined
·
248 Posts
Discussion Starter · #3 ·
SQ GT-S: does your Am & Fm reception suck or just the Am? Do they make Y adapters or is that a DIY thing?
 

·
Registered
Joined
·
1,586 Posts
Actually, my AM reception is fine. I don't listen to it much, but it comes in as clear as AM possibly could. My major problem is FM. I don't get the reception my factory radio or any of my other vehicles get.

The Y adapters can be picked-up at Radio Shack, Circuit City, or any car audio shop. You will need an adapter for the little guy, though. Maybe I'll pick one up tomorrow and try it out.
 

·
Registered
Joined
·
248 Posts
Discussion Starter · #5 ·
ok, sounds easy enough. thanx for the info.
 

·
Registered
Joined
·
4,466 Posts
Sorry to resurrect an old thread, here. But, has anyone come up with a solution? In town and driving by power lines the reception (specifically of far-off AM and FM stations) really sucks! The stocker did just fine with the same antenna (S2K). So I'm blaming the smaller antenna lead (someone here called it a diffusion antenna once, I think?).

Anyway, who's gotten this done and how???

Thanks!
 

·
Electromagnetic Wave :-h
Joined
·
15,664 Posts
Diversity antenna.... one in the rear window & the other is the whip.

You should be using the larger connector. S2K antenna will have reduced range compared to the full length whip. It will be more noticeable on further stations. It is also possible that your aftermarket radio has less sensitivity (range) than the OEM.
 

·
Registered
Joined
·
4,466 Posts
2way said:
Diversity antenna.... one in the rear window & the other is the whip.

You should be using the larger connector. S2K antenna will have reduced range compared to the full length whip. It will be more noticeable on further stations. It is also possible that your aftermarket radio has les sensitivity (range) than the OEM.
I hear everything you're saying. But I still want my diversity antenna hooked up, too. Has anyone found a solution?

Thanks.
 

·
Electromagnetic Wave :-h
Joined
·
15,664 Posts
You can get the Y adapter & a GM adapter (I think that'll fit... not sure) for the small connector & join them. It won't be diversity, but might gain you a little.. but not much.... maybe 2-3db of signal.
 

·
Registered
Joined
·
594 Posts
I dont know if it's everyone that has a problem though. I listen to AM once in a while, and fm as well. I live about 20 miles away from the nearest AM tower and 40 miles away from the nearest FM tower, and with only the one antenna plugged into my hu (jvc kd-avx1) my reception is great, for am and fm. I actually think it' better with the one plugged in the most other cars.
 

·
Registered
Joined
·
4,466 Posts
I do a lot of driving and can tell the differences at distance with terrain - including downtowns (tall buildings), dips, etc. I was blown away by the stocker's reception, frankly. It beat the crap out of most car radios I'd ever seen.

Moving to a JVC HU, running along power lines or through a downtown at 50 miles for an AM station it disappears, etc. Just looking for a better option - that thing's there for a reason.

Thanks for all your input, folks!
 

·
Electromagnetic Wave :-h
Joined
·
15,664 Posts
If you listen alot to AM... the longer the antenna, the better... S2K isn't very long... you might benefit adding the rear window antenna with the Y adapter & a GM adapter to give you more if you're going to continue to use the S2K. I'll see if I can find the parts @ RS for ya.
 

·
Electromagnetic Wave :-h
Joined
·
15,664 Posts

·
Registered
Joined
·
4,466 Posts
Damn, no technical info to go off of either. I can't be the only one that's tried to tackle this... *Laugh*
 

·
Electromagnetic Wave :-h
Joined
·
15,664 Posts
2KGTS said:
Damn, no technical info to go off of either.
Huh?

OK... here's the lesson...

A true diversity antenna system utilizes two or more antennas and internal to the radio there are essentially two receivers, the radio chooses which antenna has the best signal at any given moment. The idea being the physical antenna separation figures that while the signal may fade @ one antenna.... it won't fade equally between the two. There's a certain probability that one of the 2 will have a higher signal and that will be the one chosen @ that instant. There can also be some noise cancellation done between the 2. All depends on how fancy they get with the receivers. http://en.wikipedia.org/wiki/Antenna_diversity

A co-phased antenna system utilizes two antennas joined together to provide directivity & gain in that direction. By using the Y... you can come close to a co-phased system. However, the antenna impedance will be incorrect. Each of the 2 antennas are @ 75 ohm impedence. To reach 75 ohms @ the radio... each antenna would need an impedance of 150 ohms.

Most mobile radio antennas are 1/4 wavelength in length. The Celica's stock whip is the appropriate 1/4 wavelength length for FM use. I have not measured the rear window antenna length. Neither will be long enough to be 1/4 wavelength for the much lower AM frequencies.

I am not sure of the exact mechanism that the OEM radio uses the diverse antennas. Diversity reception would be more appropriate for FM reception where multi-path is more of a problem. I do know that I tap into my rear whip for scanner reception and it does impact AM reception. So, I don't think that it utilizes one antenna for AM & one for FM. It is more likely that AM utilizes the whip and FM is diversity reception between the 2 antennas. Especially where FM stations tend to be circularly polarized.

In the case of the Celica, one of the antennas is nearly vertically polarized (the whip) and the other is horizontally polarized (the rear window).

The S2K is a "loaded" antenna. It is essentially the same length as the stock whip, except that it is a wire which is wound circularly to reduce the overall height. This coiling and reduction in height IS going to reduce the range of the antenna.

To improve your reception w/what you have, you can try using the Y..... using the rear window antenna only, go back to a stock length whip, or add an external antenna amplifier (this is what the Matrix & Corolla do to use their smaller antennas). Otherwise.... you're looking at finding a more sensitive receiver.



These are the specs for the JVC KV-ADX1:
FM
Frequency Range: 87.5 - 107.9 MHz
Usable Sensitivity: 11.3dBf (1.0 uV/75 ohms)
50dB Quieting Sensitivity: 16.3 dBf (1.8 uV/75 ohms)
Stereo Separation: 35dB
Capture Ratio: 1.5dB

AM
Frequency Range: 530 - 1710 kHz
Sensitivity: 20 uV
Selectivity: 35 dB

A Kenwood DPX701 has:
FM
Usable Sensitivity: 9.3dBf (0.8 uV/75 ohms)
50dB Quieting Sensitivity: 15.2 dBf (1.6 uV/75 ohms)
AM
Sensitivity: 25 uV

You can see that the Kenwood has a better FM receiver. But, has a worse AM one. The FM usable sens is 30db of quieting. The 50db quieting sensitivity (20db above usable) is the RF level it takes (w/o modulation) to accomplish 50db of "quiet" vs. complete noise (no signal) at the speakers. The AM specs are for 20db quieting.
 

·
Registered
Joined
·
4,466 Posts
Whoa.

Well, my education for the day. You clearly know your stuff and I greatly appreciate your input and time!

When I said no technical data, I meant on the GM part. It doesn't say what size the smaller plug actually is. In other words, it's tough to say what size the "mini-GM" lead is in order to see if it might fit the Celica diversity lead. And, of course, after reading all you've said, it doesn't sound worth it. Either go back to the whip or try an antenna amplifier.

That begs the questions: a) are any of the external antenna amplifiers worth the trouble? and b) do any of them fit an application with the Celica/S2K antenna and the JVC radio?
 

·
Electromagnetic Wave :-h
Joined
·
15,664 Posts
Yeah.. I can't guarantee that the smaller connector is a GM style... but, sure looks to be.

a) really depends. I know they've improved things since I last used one... lol. Typically, they are only good for rural areas to pick up a distant station. On FM, they will tend to add hiss... and if you are near a FM station.. it could overload the receiver with signal.... basically swamping the receiver... making it hard for your receiver to hear the station you want. I've no experience w/one on AM.

b) most any of them will fit the S2K application.. HU is of little consequence.

An antenna amplifier can only amplify a signal that is there and make it stronger.... if the antenna is too short to even receive some amount of signal... .there's nothing for the amplifier to amplify but noise.

Really, if you're trying to listen to AM... longer is definitely better. Consider returning to the whip, go to a normal length motorized antenna (even lower profile than a S2K when lowered), find an aftermarket windshield wire antenna, or try a GM adapter w/the rear window antenna (probably pretty much the same as an aftermarket window antenna).

About the only other alternative that I can think of that might be worth trying is yanking the antenna & amp assembly from a junked Corolla or Matrix...... certainly don't want to buy a new one..... they're almost $300. But, I've no idea if it'll even fit on a Celica.
 

·
Registered
Joined
·
4,466 Posts
Thanks again!
 

·
Electromagnetic Wave :-h
Joined
·
15,664 Posts
NP Good Luck!
 
1 - 20 of 20 Posts
Top