FM Radio Reception Signal - Honda Prelude Forum

abadv8 · 04-06-2011, 10:19 PM

Hello All,

Before anyone drops the "search" bomb, as seems to be the tradition for dumb questions, I did search this. However, I think that my terminology may differ a bit from what would be considered conventional (it's probably just the engineer in me spilling over into reality). I am looking for common issues that cause degradation of FM radio reception, specific to the Honda Prelude platform. I searched "radio reception" and "radio signal", but did not turn up any particularly useful results.

Now that we've gotten the formalities out of the way... what we have here is a '93 Prelude VTEC (I believe that's correct term for the model, but have also seen this model listed as Si) with an older Alpine head unit. FM reception is very poor. The power antenna is non-functional. However, I would tend to believe that as long as it is in the extended position it should not suffer any loss of reception (I could be totally wrong here). Is there a common mode of failure on these cars with respect to the antenna system?

Past experience leads me to believe that the problems are more of Honda thing than a Prelude thing. I had a '93 Civic coupe that exhibited the same poor performance with respect to radio reception. I never did pin point the cause of those problems. One thing that I have noted with the Prelude is that Honda did not seem to do a very good job of eliminating induced voltage or EMI, as evidenced by the faint whine from the speakers that varies with engine RPM. This tells me that there is likely a deficiency in the L-C circuit leaving the alternator, allowing the induced voltage spikes to be passed into the power system. Although, I could be totally wrong...

Anyway, I am just wondering if anyone else has had similar experiences and what you might have done to correct the problem... or did you just deal with it?

Thanks for taking the time to read my post. I know that PO has been a source of many hours of entertainment for me, and there are some very knowledgeable people here. So, thank you for any info that you might be able to share.

Oh yeah, I forgot to pose my obligatory newb question... I wanna turbo my "veetack" H22. Can I run 50 pounds of boost with a stock air filter valve, yo?

Thanks guys (and girls).

jkoni426 · 04-07-2011, 06:52 AM

If you can hear the antenna motor run when you turn on/off the radio but the mast doesn't extend/retract, you probably just have a broken mast. It's a pretty common problem and easily replaced with a new one. The radio doesn't work very well without the mast extended at least a little bit.

If you can't hear the motor running, it's either disconnnected or broken.

rjr1622 · 04-07-2011, 07:24 AM

Or its the older Alpine radio introducing the engine noise. Never had an issue with my 91 civic (to this day), 97 prelude, 93 accord (to this day) or my 97 civic :-)

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abadv8 · 04-07-2011, 11:27 AM

Jkoni,

Yeah the electromechanical part of the antenna is completely defunct. It does not raise with power. The only benefit of that, is that it also does not retract. It's basically a fixed length antenna at this point. I wouldn't think that the failure of the drive motor would have much to do with the quality of reception.

I honestly never thought to check the connection at the antenna. I just assumed that since the antenna was stuck in the extended position that the motor had simply failed.

Rjr,

I don't think that it's radio itself. Since I use exclusively Alpine head units, I am able to easily swap head units from one vehicle to another. This same head unit in another vehicle exhibits no problems with reception or interference. Likewise, known good head units still show degraded reception in the Prelude. For this reason, I attributed the problems that I was seeing in the Prelude to the chassis, and not the radio. I just assumed that Hondas did not have the best power regulation. I suppose it could very well be due to the age and condition of the alternator as well. As a side note, I am using the supplied ferrite core choke/filter that ships with the head units. The other vehicles do not need this device, and still exhibit superior reception.

I think the first thing to try is to check the connection at the antenna. If that brings no joy, in terms of a solution, then I can work my way back to the head unit, testing and replacing components as necessary (which is what, just the antenna and coaxial cable?).

It's interesting to hear that you have had no issues with noise in your previous Hondas. I guess that I'm just lucky.

One point of curiosity though, how is/was your head unit wired? Did you pull new wires to the head unit from the battery or fuse block, or did you simply use the existing wires from the OE dash harness?

Thanks again.

rjr1622 · 04-07-2011, 01:48 PM

OEM wires, except the civic.. OEM wires at first and then constant power to battery and ground to chassis as it was a 60Wx4 Alpine and I did get a little more output that way. Oh, and I've been professional installing mobile electronics for over 14 years so I've done quite a few Honda's that weren't my own too

As said above it very well could be the antenna its self (where the mast connects to coax feed) as it can leak and rust over time inside the antenna assembly as well

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g0ku · 04-07-2011, 06:20 PM

Time to install a new antenna me thinks. If it was anything like mine it started to have those issues when the motor got worn out and didn't retract all the way which in turn accelerated the rusting process.