QuestionHi Jerry,
Thank you for the timely and informative response. I noticed something driving the car last night I had not noticed before. I was sitting in a left turn lane waiting to turn, and everytime a car would pass me on the right, the gurgling sound on AM would flucuate. I could have closed my eyes and told you when a car was passing just from the sound.
But searching for this is still working with the aftermarket antenna's and that is not ideal. One suggestion Alpine Tech had was maybe the Alpine unit did not supply the correct power to the antenna module. Remember, when the module had no power, we had good FM, but no AM. Then we applied power and got AM "clear", but the FM had "crackling". They felt Ovation, a leading electronics installer here in Kentucky and Indiana, should test the power output from the Alpine unit and compare it to the factory unit. This would be easy since the factory unit is still in the car and functioning.
I suggested maybe they just power the antenna module from the factory unit, therefore no change in strength from factory install. Another thought was to go straight to the battery or fuse block for power. This crackling noise seems to be power from all indications I get from people I have consulted. As I mentioned, when I mentioned this to Ovation, they expressed design allows for power changes since an automobile varies in voltage depending on load and driving conditions. So they did not feel this as a strong possibility even though their own Alpine distributor suggested they test this as a source. If I could get rid of the noise from the FM, we would be back on factory antenna, have clear AM, which is usually difficult to do, and all would be happy.
You also said, "The input and output impedances of the radio and the factory booster may not be matched very well, causing the noise problems."
Can you refine this anymore? I thought the booster was mainly for AM, since it has no "ground plane" for the antenna base? And when the module had no power we had clear FM but no AM.
Anything technical you may lend to my argument to persuade them to persue this would help.
Again thanks for your time and knowledge.
Dwight
-------------------------
Followup To
Question -
I had Ovation professionally install in a Cadillac Seville 2002 SLS non-Bose, an Alpine CDA9833, JLA E6450 along with BA speakers. The factory head unit is mounted in right trunk area, power on, to retain OnStar and Chime Alarm, through two 2" speaker we mounted in the dash just for this.
When Ovation gave me my car back it had clear FM but no AM. They left the power wire off of the GM antenna module. When they applied power, I guess from the Alpine head unit supply, it gave me clear AM, but the FM had a crackling noise in it. They tried chokes, grounds....and finally installed two aftermarket antennas on the inside top of the front windshield and unhooked the factory antenna.
Now I have "fringy" FM, and a noise on the AM that sounds like "gurgling" on all freq. but it varies on different freq. and waves with movement. It is more pronounced when going under overpasses, so this indicates to me it is in the background always, and is just covered up by music on strong stations. It is almost like something from outerspace, and the Ovation mgr thinks it sounds like computer information or noise from the car computer. Two shops have suggested they go back to the factory antenna, and find the source of the noise on FM and illiminate it. (I like this suggestion).
Seems Ovation doesn't totally agree with those suggestions and feeling the noise on AM may be computer noise, have asked me to bring the car back in and supposedly the store mgr, asst mgr, installer, and Alpine man will work on it. They also keep insisting Alpine does not support strong AM reception, but Alpine says their AM reception is as good as any on the market.
The sound is very good on CD, but this antenna problem is messing AM, FM up unreasonably so. I would feel better using the GM power antenna modules; and with no power, clear FM - add power, clear AM, crackling noise FM, I feel this should say something. I am not familiar enough to know what would cause crackling noise on FM or why / how the antenna power module works in GM to make sense of this.
I can't help but feel as if they have done something in the installation like most of us do when we check everything looking for a problem only to find out it was a "fuse" to start with.
Any suggestions would be appreciated.
Thanks,
Dwight
Answer -
Interesting situation, Dwight.
But one of the 1st things that comes to mind is that once you have a good 'system', the weakest source link (radio wave reception in a mobile environment) will always stand out as a problem.
Multipath and other forms of interference are very common (but not so well perceived in most factory systems).
Though I prefer Clarions for overall performance and flexibility, that Alpine should have (I know they used to have) an 'antenna trimmer' for adjusting its AM reception performance. This is a common feature in moderate to high end head units.
If the simple trimmer adjustement cannot cure the AM problem, the head unit may be a lemon.
What I would like say is to try a variable FM booster (user adjustable) for the FM section, but since the FM never had a problem until the booster was wired up again, having an FM booster at all seems rather futile and uneeded with this new head unit.
This is a tricky deal to explain to you.. see, the new radios' reception is much greater than the factory one (at least for FM). The input and output impedances of the radio and the factory booster may not be matched very well, causing the noise problems.
What might be best now, is to try an after market FM booster that has a level control the user can adjust if the reception is poor (or too strong).
From what you said, it seems that the factory antenna booster did cure the AM but made the FM too sensitive.
"Two shops have suggested they go back to the factory antenna, and find the source of the noise on FM and illiminate it"
I could not agree more!!
It could BE the computer in the caddy ...but it is the installers job to understand, adapt and overcome it. Let them take it back and work on it.
Good luck with these 'ovationers'.
Sincerely,
Jerry Mael
AnswerWhat I meant was, that from a purely RF aspect, impedance line matching to the load (antenna) is paramount for correct antenna gain. Anything but a perfect match equates to less than optimal performance. Boosters can effect either AM and FM (or both depending on design) as you have seen, but are generally for FM. Most systems will not need 'line transformers' or the likes, to better match the loads. However, these 'impedance matching networks' are very common in esoteric ham radio setups or any high-priority RF system, ect.
Of course, I would not classify any FM or AM as a 'high-priority' RF source, but antenna impedance (gain) could easily be a factor in this case.
While this project is still being done by Ovation, I would let them do their deal.
If they want to disregard their own Alpine Reps, that may be an indicator as to their degree of professionalism and zeallousness in getting this matter solved ASAP. To be fair to Ovation: It may also be the right thing to do in this case, at this time, in their eyes.
I cannot talk bad about the gear or the installers. Once you have entrusted a shop with you vehicle, your choices are to 'go with what they say'.. or not (and 'not' generally means taking your business elsewhere).
Debating issues with them in person is one thing, but arguing with them via 3rd party source (me for instance), can and will lead to bad rapports in almost all cases.
It is kind of like having a 3rd party 'QA' tech their watching them (but only through your eyes). Which is good for YOU (customer), but intimidating for most shops.
To be honest, I would not doubt it is the relocation of the factory head unit that is causing this, but without being there to go through the proper steps to isolate noise, I cannot prove or disprove anything. :(
And yes, using the factory radio to power the antenna module would be one place to start.
This must be very difficult for you to sit through on that end (I have no idea how long they have been in your car) and I really hope they get your problem resolved as soon as possible, Dwight.
Good luck and thanks for the feedback.
Sincerely,
Jerry Mael
