Antenna Amplifier for my Car

sign216 · May 3, 2016

Would an antenna amp for my car be useful?

Car is a 2006 Mazda 6. It has a "sharkfin" antenna in place of the factory whip antenna, but this reduces the reception. From the factory it comes with an antenna amplifier, but I'd like to add another to get better radio broadcasts.
Would the second amp just increase noise and reduce the signal quality, or would it be useful?

I was hoping to use the Velleman kit, or this circuit I pulled off an old post on this forum (see attached).

**broken link removed**

**broken link removed**

**broken link removed**

MikeMl · May 3, 2016

sign216 said:
Would an antenna amp for my car be useful?
...
Would the second amp just increase noise and reduce the signal quality, or would it be useful?
...

What problem are you trying to solve? Multipath, flutter, long distance from transmitters, overload/intermod due to strong nearby station.

sign216 · May 3, 2016

My problem is weak reception. Stations that come in ok on other cars, I don't get at all, or they are too weak to listen too.
I apologize for my inexperienced understanding of radio; I don't think there's overload, multipath, or flutter.

The commercial FM stations I'm trying to pull are about 12 to 40 miles away. The stations at the far end don't really come in at all. Tonight I'll check, and give you the real distances of the broadcasts I'd like to get.

MikeMl · May 3, 2016

What is the radio? Who installed it?

Mikebits · May 3, 2016

Yipes, I did not realize one of your attached files was in word format, I sure hope it does not have a virus as I already clicked on it, but quickly disabled it. Please don't post word docs, pdf is better. I won't knowingly open MS office files from unknown sources. Thanks

Mikebits · May 3, 2016

I doubt these amp kits will help much, best bet is to get a better radio, or I hear satellite radio is the way to go these days.

sign216 · May 3, 2016

MikeMl said:
What is the radio? Who installed it?

It has Mazda's premium system by Bose, which was the best Mazda put in their cars in 2006.

Getting another radio might be better, or might not at all.

Mikebits · May 3, 2016

sign216 said:
It has Mazda's premium system by Bose, which was the best Mazda put in their cars in 2006.

Getting another radio might be better, or might not at all.

Well shoot, Bose is like top notch.

audioguru · May 4, 2016

It seems that the problem is the "sharkfin antenna" whatever that is (too small?), the problem is not the radio. The extremely simple FM booster will simply get severely overloaded if you ever drive into a city with some FM stations. The strongest few stations will be mixed together and across the entire dial.

sign216 · May 5, 2016

I'd like to keep the "sharkfin" antenna. In addition to the Velleman kit in the first post, I found a Ramsey kit.
The Ramsey unit looks slightly more sophisticated than the simple Velleman one. What do you think?

An earlier Ramsey manual admits that the units by Heathkit and MFJ do a better job, but those are around $100, so for that price they should be better.

audioguru · May 5, 2016

The antenna amplifier works completely differently to a half-decent receiver design therefore it is easily overloaded:
1) A receiver has a tuned input so only the signal frequency you want is passed further into the circuit. The simple antenna amplifier is not tuned so it amplifies and is overloaded by the hundreds of signals that you do not want.
2) A receiver has automatic gain control on its input transistor so when the one signal it selects is strong it turns down its gain so it does not become overloaded and when the signal is weak it has full gain. The simple antenna amplifier is always at the gain it is set at.

My cheap Sony Walkman portable FM radio has a local-distant switch that attenuates its antenna signal to prevent strong stations from appearing all across the dial because its input is untuned and has no AGC. Its switch is always set to "local" to avoid overload then it cannot receive medium to distant stations.

sign216 · May 5, 2016

So Uncle,
Is the Velleman or the Ramsey design is better? Or neither?

They must have some use, after all, my car was designed with an antenna amp. I just want to add a second.

JimB · May 5, 2016

sign216 said:
my car was designed with an antenna amp. I just want to add a second.

I suggest that there is something wrong with the original amplifier.
Adding a second (working) amplifier is probably a bad idea.

How does the radio perform on its own?
Does it receive with a length of wire (say 1 metre long) connected directly into its antenna socket?

If the radio is OK on its own, I suggest that you look at the original amplifier and the cable connecting it to the radio, before adding an extra amplifier.

JimB

MikeMl · May 5, 2016

You can have a shark fin antenna, which isn't worth a damn for anything except "looking cool", or you can have a decent FM antenna (1/4 lambda monopole whip) which is a "real" antenna.

MikeM
(55 years of drilling holes in car roofs to mount antennas of all sorts, mostly for Ham, Public Safety, and commercial VHF/UHF two-way radios)

JimB · May 5, 2016

MikeMl said:
You can have a shark fin antenna, which isn't worth a damn for anything except "looking cool", or you can have a decent FM antenna (1/4 lambda monopole whip) which is a "real" antenna.

I agree 100%

The sharkfin antenna is a ridiculous triumph of form over function.

JimB

sign216 · May 5, 2016

The radio + factory amp appears to function fine, I'm just in a slightly rural area. Unfortunately the factory amp is buried in the C pillar of the car, and not easy to get to, so I can't inspect or test it.

Yes, a quarter or half wave antenna would work better, but in life you make compromises. Sometimes style counts for something.

The Ramsey circuit looks better, so I'll go with that.

audioguru · May 5, 2016

The Velleman kit is garbage that will overload very easily. The Ramsey kit shows no schematic but its photo shows a gain control for you to fiddle with.
Why wasn't your Bose car radio designed to work by itself like every other car radio (why does it need an additional antenna amplifier??)?

Nigel Goodwin · May 5, 2016

audioguru said:
Why wasn't your Bose car radio designed to work by itself like every other car radio (why does it need an additional antenna amplifier??)?

Because Bose is overpriced crap?

Presumably we all know that BOSE stands for "Buy Other Sound Equipment"

audioguru · May 5, 2016

My American cars always had the radio antenna in the windshield glass, not as a whip sticking up. They worked fine.

bountyhunter · May 5, 2016

sign216 said:
I'd like to keep the "sharkfin" antenna. In addition to the Velleman kit in the first post, I found a Ramsey kit.
The Ramsey unit looks slightly more sophisticated than the simple Velleman one. What do you think?

An earlier Ramsey manual admits that the units by Heathkit and MFJ do a better job, but those are around $100, so for that price they should be better.

You don't have the info to answer the question: an antenna amp will help if and only if you have a decent quality (signal to noise) signal that is just too low for the AGC range of the FM receiver. Any receiver is designed to handle signals in a specific range. The signal level depends on how good the antenna is and how strong the signal is coming from the station.

Based on info given, I suspect you need a better antenna.

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